diff --git a/baselines/dom.generated.d.ts b/baselines/dom.generated.d.ts
index ed0f93dfd..5c8d9e791 100644
--- a/baselines/dom.generated.d.ts
+++ b/baselines/dom.generated.d.ts
@@ -10035,7 +10035,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/anchors)
      */
-    readonly anchors: HTMLCollectionOf<HTMLAnchorElement>;
+    readonly anchors: HTMLCollection<HTMLAnchorElement>;
     /**
      * The **`applets`** property of the Document returns an empty HTMLCollection.
      * @deprecated
@@ -10140,7 +10140,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/embeds)
      */
-    readonly embeds: HTMLCollectionOf<HTMLEmbedElement>;
+    readonly embeds: HTMLCollection<HTMLEmbedElement>;
     /**
      * **`fgColor`** gets/sets the foreground color, or text color, of the current document.
      * @deprecated
@@ -10153,7 +10153,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/forms)
      */
-    readonly forms: HTMLCollectionOf<HTMLFormElement>;
+    readonly forms: HTMLCollection<HTMLFormElement>;
     /**
      * The **`fragmentDirective`** read-only property of the Document interface returns the FragmentDirective for the current document.
      *
@@ -10190,7 +10190,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/images)
      */
-    readonly images: HTMLCollectionOf<HTMLImageElement>;
+    readonly images: HTMLCollection<HTMLImageElement>;
     /**
      * The **`Document.implementation`** property returns a A DOMImplementation object.
      *
@@ -10221,7 +10221,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/links)
      */
-    readonly links: HTMLCollectionOf<HTMLAnchorElement | HTMLAreaElement>;
+    readonly links: HTMLCollection<HTMLAnchorElement | HTMLAreaElement>;
     /**
      * The **`Document.location`** read-only property returns a and provides methods for changing that URL and loading another URL.
      *
@@ -10253,7 +10253,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/plugins)
      */
-    readonly plugins: HTMLCollectionOf<HTMLEmbedElement>;
+    readonly plugins: HTMLCollection<HTMLEmbedElement>;
     /**
      * The **`Document.readyState`** property describes the loading state of the document.
      *
@@ -10278,7 +10278,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/scripts)
      */
-    readonly scripts: HTMLCollectionOf<HTMLScriptElement>;
+    readonly scripts: HTMLCollection<HTMLScriptElement>;
     /**
      * The **`scrollingElement`** read-only property of the scrolls the document.
      *
@@ -10525,7 +10525,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/getElementsByClassName)
      */
-    getElementsByClassName(classNames: string): HTMLCollectionOf<Element>;
+    getElementsByClassName(classNames: string): HTMLCollection;
     /**
      * The **`getElementsByName()`** method of the Document object returns a NodeList Collection of elements with a given `name` attribute in the document.
      *
@@ -10537,21 +10537,21 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/getElementsByTagName)
      */
-    getElementsByTagName<K extends keyof HTMLElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<HTMLElementTagNameMap[K]>;
-    getElementsByTagName<K extends keyof SVGElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<SVGElementTagNameMap[K]>;
-    getElementsByTagName<K extends keyof MathMLElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<MathMLElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof HTMLElementTagNameMap>(qualifiedName: K): HTMLCollection<HTMLElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof SVGElementTagNameMap>(qualifiedName: K): HTMLCollection<SVGElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof MathMLElementTagNameMap>(qualifiedName: K): HTMLCollection<MathMLElementTagNameMap[K]>;
     /** @deprecated */
-    getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(qualifiedName: K): HTMLCollectionOf<HTMLElementDeprecatedTagNameMap[K]>;
-    getElementsByTagName(qualifiedName: string): HTMLCollectionOf<Element>;
+    getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(qualifiedName: K): HTMLCollection<HTMLElementDeprecatedTagNameMap[K]>;
+    getElementsByTagName(qualifiedName: string): HTMLCollection;
     /**
      * Returns a list of elements with the given tag name belonging to the given namespace.
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/getElementsByTagNameNS)
      */
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1999/xhtml", localName: string): HTMLCollectionOf<HTMLElement>;
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/2000/svg", localName: string): HTMLCollectionOf<SVGElement>;
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1998/Math/MathML", localName: string): HTMLCollectionOf<MathMLElement>;
-    getElementsByTagNameNS(namespace: string | null, localName: string): HTMLCollectionOf<Element>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1999/xhtml", localName: string): HTMLCollection<HTMLElement>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/2000/svg", localName: string): HTMLCollection<SVGElement>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1998/Math/MathML", localName: string): HTMLCollection<MathMLElement>;
+    getElementsByTagNameNS(namespace: string | null, localName: string): HTMLCollection;
     /**
      * The **`getSelection()`** method of the Document interface returns the Selection object associated with this document, representing the range of text selected by the user, or the current position of the caret.
      *
@@ -11159,27 +11159,27 @@ interface Element extends Node, ARIAMixin, Animatable, ChildNode, NonDocumentTyp
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Element/getElementsByClassName)
      */
-    getElementsByClassName(classNames: string): HTMLCollectionOf<Element>;
+    getElementsByClassName(classNames: string): HTMLCollection;
     /**
      * The **`Element.getElementsByTagName()`** method returns a live All descendants of the specified element are searched, but not the element itself.
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Element/getElementsByTagName)
      */
-    getElementsByTagName<K extends keyof HTMLElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<HTMLElementTagNameMap[K]>;
-    getElementsByTagName<K extends keyof SVGElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<SVGElementTagNameMap[K]>;
-    getElementsByTagName<K extends keyof MathMLElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<MathMLElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof HTMLElementTagNameMap>(qualifiedName: K): HTMLCollection<HTMLElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof SVGElementTagNameMap>(qualifiedName: K): HTMLCollection<SVGElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof MathMLElementTagNameMap>(qualifiedName: K): HTMLCollection<MathMLElementTagNameMap[K]>;
     /** @deprecated */
-    getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(qualifiedName: K): HTMLCollectionOf<HTMLElementDeprecatedTagNameMap[K]>;
-    getElementsByTagName(qualifiedName: string): HTMLCollectionOf<Element>;
+    getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(qualifiedName: K): HTMLCollection<HTMLElementDeprecatedTagNameMap[K]>;
+    getElementsByTagName(qualifiedName: string): HTMLCollection;
     /**
      * The **`Element.getElementsByTagNameNS()`** method returns a live HTMLCollection of elements with the given tag name belonging to the given namespace.
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Element/getElementsByTagNameNS)
      */
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1999/xhtml", localName: string): HTMLCollectionOf<HTMLElement>;
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/2000/svg", localName: string): HTMLCollectionOf<SVGElement>;
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1998/Math/MathML", localName: string): HTMLCollectionOf<MathMLElement>;
-    getElementsByTagNameNS(namespace: string | null, localName: string): HTMLCollectionOf<Element>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1999/xhtml", localName: string): HTMLCollection<HTMLElement>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/2000/svg", localName: string): HTMLCollection<SVGElement>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1998/Math/MathML", localName: string): HTMLCollection<MathMLElement>;
+    getElementsByTagNameNS(namespace: string | null, localName: string): HTMLCollection;
     /**
      * The **`getHTML()`** method of the Element interface is used to serialize an element's DOM to an HTML string.
      *
@@ -13688,7 +13688,7 @@ declare var HTMLCanvasElement: {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLCollection)
  */
-interface HTMLCollectionBase {
+interface HTMLCollectionBase<E extends Element = Element, N = never> {
     /**
      * The **`HTMLCollection.length`** property returns the number of items in a HTMLCollection.
      *
@@ -13700,17 +13700,17 @@ interface HTMLCollectionBase {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLCollection/item)
      */
-    item(index: number): Element | null;
-    [index: number]: Element;
+    item(index: number): E | null;
+    [index: number]: E;
 }
 
-interface HTMLCollection extends HTMLCollectionBase {
+interface HTMLCollection<E extends Element = Element, N = never> extends HTMLCollectionBase {
     /**
      * The **`namedItem()`** method of the HTMLCollection interface returns the first Element in the collection whose `id` or `name` attribute match the specified name, or `null` if no element matches.
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLCollection/namedItem)
      */
-    namedItem(name: string): Element | null;
+    namedItem(name: string): E | N | null;
 }
 
 declare var HTMLCollection: {
@@ -13718,12 +13718,6 @@ declare var HTMLCollection: {
     new(): HTMLCollection;
 };
 
-interface HTMLCollectionOf<T extends Element> extends HTMLCollectionBase {
-    item(index: number): T | null;
-    namedItem(name: string): T | null;
-    [index: number]: T;
-}
-
 /**
  * The **`HTMLDListElement`** interface provides special properties (beyond those of the regular HTMLElement interface it also has available to it by inheritance) for manipulating definition list (dl) elements.
  *
@@ -13782,7 +13776,7 @@ interface HTMLDataListElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLDataListElement/options)
      */
-    readonly options: HTMLCollectionOf<HTMLOptionElement>;
+    readonly options: HTMLCollection<HTMLOptionElement>;
     addEventListener<K extends keyof HTMLElementEventMap>(type: K, listener: (this: HTMLDataListElement, ev: HTMLElementEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
     removeEventListener<K extends keyof HTMLElementEventMap>(type: K, listener: (this: HTMLDataListElement, ev: HTMLElementEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
@@ -14284,7 +14278,7 @@ declare var HTMLFontElement: {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLFormControlsCollection)
  */
-interface HTMLFormControlsCollection extends HTMLCollectionBase {
+interface HTMLFormControlsCollection extends HTMLCollection<Element, RadioNodeList> {
     /**
      * The **`HTMLFormControlsCollection.namedItem()`** method returns the RadioNodeList or the Element in the collection whose `name` or `id` match the specified name, or `null` if no node matches.
      *
@@ -15522,7 +15516,7 @@ interface HTMLMapElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLMapElement/areas)
      */
-    readonly areas: HTMLCollection;
+    readonly areas: HTMLCollection<HTMLAreaElement>;
     /**
      * The **`name`** property of the HTMLMapElement represents the unique name `<map>` element.
      *
@@ -16296,7 +16290,7 @@ declare var HTMLOptionElement: {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLOptionsCollection)
  */
-interface HTMLOptionsCollection extends HTMLCollectionOf<HTMLOptionElement> {
+interface HTMLOptionsCollection extends HTMLCollection<HTMLOptionElement> {
     /**
      * The **`length`** property of the HTMLOptionsCollection interface returns the number of option elements in the collection.
      *
@@ -16752,7 +16746,7 @@ interface HTMLSelectElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLSelectElement/selectedOptions)
      */
-    readonly selectedOptions: HTMLCollectionOf<HTMLOptionElement>;
+    readonly selectedOptions: HTMLCollection<HTMLOptionElement>;
     /**
      * The **`size`** property of the HTMLSelectElement interface specifies the number of options, or rows, that should be visible at one time.
      *
@@ -17255,7 +17249,7 @@ interface HTMLTableElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLTableElement/rows)
      */
-    readonly rows: HTMLCollectionOf<HTMLTableRowElement>;
+    readonly rows: HTMLCollection<HTMLTableRowElement>;
     /**
      * The **`HTMLTableElement.rules`** property indicates which cell borders to render in the table.
      * @deprecated
@@ -17275,7 +17269,7 @@ interface HTMLTableElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLTableElement/tBodies)
      */
-    readonly tBodies: HTMLCollectionOf<HTMLTableSectionElement>;
+    readonly tBodies: HTMLCollection<HTMLTableSectionElement>;
     /**
      * The **`HTMLTableElement.tFoot`** property represents the `null` if there is no such element.
      *
@@ -17393,7 +17387,7 @@ interface HTMLTableRowElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLTableRowElement/cells)
      */
-    readonly cells: HTMLCollectionOf<HTMLTableCellElement>;
+    readonly cells: HTMLCollection<HTMLTableCellElement>;
     /**
      * The **`ch`** property of the HTMLTableRowElement interface does nothing.
      * @deprecated
@@ -17482,7 +17476,7 @@ interface HTMLTableSectionElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLTableSectionElement/rows)
      */
-    readonly rows: HTMLCollectionOf<HTMLTableRowElement>;
+    readonly rows: HTMLCollection<HTMLTableRowElement>;
     /**
      * The **`vAlign`** property of the HTMLTableSectionElement interface is a string indicating how to vertically align text in a thead, tbody or tfoot table section.
      * @deprecated
diff --git a/baselines/dom.iterable.generated.d.ts b/baselines/dom.iterable.generated.d.ts
index 1c7b0f4eb..d7e82303e 100644
--- a/baselines/dom.iterable.generated.d.ts
+++ b/baselines/dom.iterable.generated.d.ts
@@ -146,14 +146,10 @@ interface HTMLAllCollection {
     [Symbol.iterator](): ArrayIterator<Element>;
 }
 
-interface HTMLCollectionBase {
+interface HTMLCollectionBase<E extends Element = Element, N = never> {
     [Symbol.iterator](): ArrayIterator<Element>;
 }
 
-interface HTMLCollectionOf<T extends Element> {
-    [Symbol.iterator](): ArrayIterator<T>;
-}
-
 interface HTMLFormElement {
     [Symbol.iterator](): ArrayIterator<Element>;
 }
diff --git a/baselines/serviceworker.generated.d.ts b/baselines/serviceworker.generated.d.ts
index c4b8089df..c60f37977 100644
--- a/baselines/serviceworker.generated.d.ts
+++ b/baselines/serviceworker.generated.d.ts
@@ -11489,6 +11489,8 @@ type GLsizei = number;
 type GLsizeiptr = number;
 type GLuint = number;
 type GLuint64 = number;
+/** @deprecated */
+type HTMLCollectionOf<T extends Element> = HTMLCollection<T>;
 type HashAlgorithmIdentifier = AlgorithmIdentifier;
 type HeadersInit = [string, string][] | Record<string, string> | Headers;
 type IDBValidKey = number | string | Date | BufferSource | IDBValidKey[];
diff --git a/baselines/sharedworker.generated.d.ts b/baselines/sharedworker.generated.d.ts
index b72ab2c8f..35af05efd 100644
--- a/baselines/sharedworker.generated.d.ts
+++ b/baselines/sharedworker.generated.d.ts
@@ -11178,6 +11178,8 @@ type GLsizei = number;
 type GLsizeiptr = number;
 type GLuint = number;
 type GLuint64 = number;
+/** @deprecated */
+type HTMLCollectionOf<T extends Element> = HTMLCollection<T>;
 type HashAlgorithmIdentifier = AlgorithmIdentifier;
 type HeadersInit = [string, string][] | Record<string, string> | Headers;
 type IDBValidKey = number | string | Date | BufferSource | IDBValidKey[];
diff --git a/baselines/ts5.5/dom.generated.d.ts b/baselines/ts5.5/dom.generated.d.ts
index b94da6da0..7ea6e39a2 100644
--- a/baselines/ts5.5/dom.generated.d.ts
+++ b/baselines/ts5.5/dom.generated.d.ts
@@ -10027,7 +10027,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/anchors)
      */
-    readonly anchors: HTMLCollectionOf<HTMLAnchorElement>;
+    readonly anchors: HTMLCollection<HTMLAnchorElement>;
     /**
      * The **`applets`** property of the Document returns an empty HTMLCollection.
      * @deprecated
@@ -10132,7 +10132,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/embeds)
      */
-    readonly embeds: HTMLCollectionOf<HTMLEmbedElement>;
+    readonly embeds: HTMLCollection<HTMLEmbedElement>;
     /**
      * **`fgColor`** gets/sets the foreground color, or text color, of the current document.
      * @deprecated
@@ -10145,7 +10145,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/forms)
      */
-    readonly forms: HTMLCollectionOf<HTMLFormElement>;
+    readonly forms: HTMLCollection<HTMLFormElement>;
     /**
      * The **`fragmentDirective`** read-only property of the Document interface returns the FragmentDirective for the current document.
      *
@@ -10182,7 +10182,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/images)
      */
-    readonly images: HTMLCollectionOf<HTMLImageElement>;
+    readonly images: HTMLCollection<HTMLImageElement>;
     /**
      * The **`Document.implementation`** property returns a A DOMImplementation object.
      *
@@ -10213,7 +10213,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/links)
      */
-    readonly links: HTMLCollectionOf<HTMLAnchorElement | HTMLAreaElement>;
+    readonly links: HTMLCollection<HTMLAnchorElement | HTMLAreaElement>;
     /**
      * The **`Document.location`** read-only property returns a and provides methods for changing that URL and loading another URL.
      *
@@ -10245,7 +10245,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/plugins)
      */
-    readonly plugins: HTMLCollectionOf<HTMLEmbedElement>;
+    readonly plugins: HTMLCollection<HTMLEmbedElement>;
     /**
      * The **`Document.readyState`** property describes the loading state of the document.
      *
@@ -10270,7 +10270,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/scripts)
      */
-    readonly scripts: HTMLCollectionOf<HTMLScriptElement>;
+    readonly scripts: HTMLCollection<HTMLScriptElement>;
     /**
      * The **`scrollingElement`** read-only property of the scrolls the document.
      *
@@ -10517,7 +10517,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/getElementsByClassName)
      */
-    getElementsByClassName(classNames: string): HTMLCollectionOf<Element>;
+    getElementsByClassName(classNames: string): HTMLCollection;
     /**
      * The **`getElementsByName()`** method of the Document object returns a NodeList Collection of elements with a given `name` attribute in the document.
      *
@@ -10529,21 +10529,21 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/getElementsByTagName)
      */
-    getElementsByTagName<K extends keyof HTMLElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<HTMLElementTagNameMap[K]>;
-    getElementsByTagName<K extends keyof SVGElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<SVGElementTagNameMap[K]>;
-    getElementsByTagName<K extends keyof MathMLElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<MathMLElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof HTMLElementTagNameMap>(qualifiedName: K): HTMLCollection<HTMLElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof SVGElementTagNameMap>(qualifiedName: K): HTMLCollection<SVGElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof MathMLElementTagNameMap>(qualifiedName: K): HTMLCollection<MathMLElementTagNameMap[K]>;
     /** @deprecated */
-    getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(qualifiedName: K): HTMLCollectionOf<HTMLElementDeprecatedTagNameMap[K]>;
-    getElementsByTagName(qualifiedName: string): HTMLCollectionOf<Element>;
+    getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(qualifiedName: K): HTMLCollection<HTMLElementDeprecatedTagNameMap[K]>;
+    getElementsByTagName(qualifiedName: string): HTMLCollection;
     /**
      * Returns a list of elements with the given tag name belonging to the given namespace.
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/getElementsByTagNameNS)
      */
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1999/xhtml", localName: string): HTMLCollectionOf<HTMLElement>;
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/2000/svg", localName: string): HTMLCollectionOf<SVGElement>;
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1998/Math/MathML", localName: string): HTMLCollectionOf<MathMLElement>;
-    getElementsByTagNameNS(namespace: string | null, localName: string): HTMLCollectionOf<Element>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1999/xhtml", localName: string): HTMLCollection<HTMLElement>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/2000/svg", localName: string): HTMLCollection<SVGElement>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1998/Math/MathML", localName: string): HTMLCollection<MathMLElement>;
+    getElementsByTagNameNS(namespace: string | null, localName: string): HTMLCollection;
     /**
      * The **`getSelection()`** method of the Document interface returns the Selection object associated with this document, representing the range of text selected by the user, or the current position of the caret.
      *
@@ -11149,27 +11149,27 @@ interface Element extends Node, ARIAMixin, Animatable, ChildNode, NonDocumentTyp
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Element/getElementsByClassName)
      */
-    getElementsByClassName(classNames: string): HTMLCollectionOf<Element>;
+    getElementsByClassName(classNames: string): HTMLCollection;
     /**
      * The **`Element.getElementsByTagName()`** method returns a live All descendants of the specified element are searched, but not the element itself.
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Element/getElementsByTagName)
      */
-    getElementsByTagName<K extends keyof HTMLElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<HTMLElementTagNameMap[K]>;
-    getElementsByTagName<K extends keyof SVGElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<SVGElementTagNameMap[K]>;
-    getElementsByTagName<K extends keyof MathMLElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<MathMLElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof HTMLElementTagNameMap>(qualifiedName: K): HTMLCollection<HTMLElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof SVGElementTagNameMap>(qualifiedName: K): HTMLCollection<SVGElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof MathMLElementTagNameMap>(qualifiedName: K): HTMLCollection<MathMLElementTagNameMap[K]>;
     /** @deprecated */
-    getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(qualifiedName: K): HTMLCollectionOf<HTMLElementDeprecatedTagNameMap[K]>;
-    getElementsByTagName(qualifiedName: string): HTMLCollectionOf<Element>;
+    getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(qualifiedName: K): HTMLCollection<HTMLElementDeprecatedTagNameMap[K]>;
+    getElementsByTagName(qualifiedName: string): HTMLCollection;
     /**
      * The **`Element.getElementsByTagNameNS()`** method returns a live HTMLCollection of elements with the given tag name belonging to the given namespace.
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Element/getElementsByTagNameNS)
      */
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1999/xhtml", localName: string): HTMLCollectionOf<HTMLElement>;
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/2000/svg", localName: string): HTMLCollectionOf<SVGElement>;
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1998/Math/MathML", localName: string): HTMLCollectionOf<MathMLElement>;
-    getElementsByTagNameNS(namespace: string | null, localName: string): HTMLCollectionOf<Element>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1999/xhtml", localName: string): HTMLCollection<HTMLElement>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/2000/svg", localName: string): HTMLCollection<SVGElement>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1998/Math/MathML", localName: string): HTMLCollection<MathMLElement>;
+    getElementsByTagNameNS(namespace: string | null, localName: string): HTMLCollection;
     /**
      * The **`getHTML()`** method of the Element interface is used to serialize an element's DOM to an HTML string.
      *
@@ -13675,7 +13675,7 @@ declare var HTMLCanvasElement: {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLCollection)
  */
-interface HTMLCollectionBase {
+interface HTMLCollectionBase<E extends Element = Element, N = never> {
     /**
      * The **`HTMLCollection.length`** property returns the number of items in a HTMLCollection.
      *
@@ -13687,17 +13687,17 @@ interface HTMLCollectionBase {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLCollection/item)
      */
-    item(index: number): Element | null;
-    [index: number]: Element;
+    item(index: number): E | null;
+    [index: number]: E;
 }
 
-interface HTMLCollection extends HTMLCollectionBase {
+interface HTMLCollection<E extends Element = Element, N = never> extends HTMLCollectionBase {
     /**
      * The **`namedItem()`** method of the HTMLCollection interface returns the first Element in the collection whose `id` or `name` attribute match the specified name, or `null` if no element matches.
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLCollection/namedItem)
      */
-    namedItem(name: string): Element | null;
+    namedItem(name: string): E | N | null;
 }
 
 declare var HTMLCollection: {
@@ -13705,12 +13705,6 @@ declare var HTMLCollection: {
     new(): HTMLCollection;
 };
 
-interface HTMLCollectionOf<T extends Element> extends HTMLCollectionBase {
-    item(index: number): T | null;
-    namedItem(name: string): T | null;
-    [index: number]: T;
-}
-
 /**
  * The **`HTMLDListElement`** interface provides special properties (beyond those of the regular HTMLElement interface it also has available to it by inheritance) for manipulating definition list (dl) elements.
  *
@@ -13769,7 +13763,7 @@ interface HTMLDataListElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLDataListElement/options)
      */
-    readonly options: HTMLCollectionOf<HTMLOptionElement>;
+    readonly options: HTMLCollection<HTMLOptionElement>;
     addEventListener<K extends keyof HTMLElementEventMap>(type: K, listener: (this: HTMLDataListElement, ev: HTMLElementEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
     removeEventListener<K extends keyof HTMLElementEventMap>(type: K, listener: (this: HTMLDataListElement, ev: HTMLElementEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
@@ -14271,7 +14265,7 @@ declare var HTMLFontElement: {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLFormControlsCollection)
  */
-interface HTMLFormControlsCollection extends HTMLCollectionBase {
+interface HTMLFormControlsCollection extends HTMLCollection<Element, RadioNodeList> {
     /**
      * The **`HTMLFormControlsCollection.namedItem()`** method returns the RadioNodeList or the Element in the collection whose `name` or `id` match the specified name, or `null` if no node matches.
      *
@@ -15504,7 +15498,7 @@ interface HTMLMapElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLMapElement/areas)
      */
-    readonly areas: HTMLCollection;
+    readonly areas: HTMLCollection<HTMLAreaElement>;
     /**
      * The **`name`** property of the HTMLMapElement represents the unique name `<map>` element.
      *
@@ -16278,7 +16272,7 @@ declare var HTMLOptionElement: {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLOptionsCollection)
  */
-interface HTMLOptionsCollection extends HTMLCollectionOf<HTMLOptionElement> {
+interface HTMLOptionsCollection extends HTMLCollection<HTMLOptionElement> {
     /**
      * The **`length`** property of the HTMLOptionsCollection interface returns the number of option elements in the collection.
      *
@@ -16732,7 +16726,7 @@ interface HTMLSelectElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLSelectElement/selectedOptions)
      */
-    readonly selectedOptions: HTMLCollectionOf<HTMLOptionElement>;
+    readonly selectedOptions: HTMLCollection<HTMLOptionElement>;
     /**
      * The **`size`** property of the HTMLSelectElement interface specifies the number of options, or rows, that should be visible at one time.
      *
@@ -17234,7 +17228,7 @@ interface HTMLTableElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLTableElement/rows)
      */
-    readonly rows: HTMLCollectionOf<HTMLTableRowElement>;
+    readonly rows: HTMLCollection<HTMLTableRowElement>;
     /**
      * The **`HTMLTableElement.rules`** property indicates which cell borders to render in the table.
      * @deprecated
@@ -17254,7 +17248,7 @@ interface HTMLTableElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLTableElement/tBodies)
      */
-    readonly tBodies: HTMLCollectionOf<HTMLTableSectionElement>;
+    readonly tBodies: HTMLCollection<HTMLTableSectionElement>;
     /**
      * The **`HTMLTableElement.tFoot`** property represents the `null` if there is no such element.
      *
@@ -17372,7 +17366,7 @@ interface HTMLTableRowElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLTableRowElement/cells)
      */
-    readonly cells: HTMLCollectionOf<HTMLTableCellElement>;
+    readonly cells: HTMLCollection<HTMLTableCellElement>;
     /**
      * The **`ch`** property of the HTMLTableRowElement interface does nothing.
      * @deprecated
@@ -17461,7 +17455,7 @@ interface HTMLTableSectionElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLTableSectionElement/rows)
      */
-    readonly rows: HTMLCollectionOf<HTMLTableRowElement>;
+    readonly rows: HTMLCollection<HTMLTableRowElement>;
     /**
      * The **`vAlign`** property of the HTMLTableSectionElement interface is a string indicating how to vertically align text in a thead, tbody or tfoot table section.
      * @deprecated
diff --git a/baselines/ts5.5/dom.iterable.generated.d.ts b/baselines/ts5.5/dom.iterable.generated.d.ts
index 3bf93bb9a..ddab3c71f 100644
--- a/baselines/ts5.5/dom.iterable.generated.d.ts
+++ b/baselines/ts5.5/dom.iterable.generated.d.ts
@@ -142,14 +142,10 @@ interface HTMLAllCollection {
     [Symbol.iterator](): IterableIterator<Element>;
 }
 
-interface HTMLCollectionBase {
+interface HTMLCollectionBase<E extends Element = Element, N = never> {
     [Symbol.iterator](): IterableIterator<Element>;
 }
 
-interface HTMLCollectionOf<T extends Element> {
-    [Symbol.iterator](): IterableIterator<T>;
-}
-
 interface HTMLFormElement {
     [Symbol.iterator](): IterableIterator<Element>;
 }
diff --git a/baselines/ts5.5/serviceworker.generated.d.ts b/baselines/ts5.5/serviceworker.generated.d.ts
index 42749c941..1a68b35a1 100644
--- a/baselines/ts5.5/serviceworker.generated.d.ts
+++ b/baselines/ts5.5/serviceworker.generated.d.ts
@@ -11489,6 +11489,8 @@ type GLsizei = number;
 type GLsizeiptr = number;
 type GLuint = number;
 type GLuint64 = number;
+/** @deprecated */
+type HTMLCollectionOf<T extends Element> = HTMLCollection<T>;
 type HashAlgorithmIdentifier = AlgorithmIdentifier;
 type HeadersInit = [string, string][] | Record<string, string> | Headers;
 type IDBValidKey = number | string | Date | BufferSource | IDBValidKey[];
diff --git a/baselines/ts5.5/sharedworker.generated.d.ts b/baselines/ts5.5/sharedworker.generated.d.ts
index e1dd7e2be..827716a1a 100644
--- a/baselines/ts5.5/sharedworker.generated.d.ts
+++ b/baselines/ts5.5/sharedworker.generated.d.ts
@@ -11178,6 +11178,8 @@ type GLsizei = number;
 type GLsizeiptr = number;
 type GLuint = number;
 type GLuint64 = number;
+/** @deprecated */
+type HTMLCollectionOf<T extends Element> = HTMLCollection<T>;
 type HashAlgorithmIdentifier = AlgorithmIdentifier;
 type HeadersInit = [string, string][] | Record<string, string> | Headers;
 type IDBValidKey = number | string | Date | BufferSource | IDBValidKey[];
diff --git a/baselines/ts5.5/webworker.generated.d.ts b/baselines/ts5.5/webworker.generated.d.ts
index be3f9748b..6ab5bf35d 100644
--- a/baselines/ts5.5/webworker.generated.d.ts
+++ b/baselines/ts5.5/webworker.generated.d.ts
@@ -13146,6 +13146,8 @@ type GLsizei = number;
 type GLsizeiptr = number;
 type GLuint = number;
 type GLuint64 = number;
+/** @deprecated */
+type HTMLCollectionOf<T extends Element> = HTMLCollection<T>;
 type HashAlgorithmIdentifier = AlgorithmIdentifier;
 type HeadersInit = [string, string][] | Record<string, string> | Headers;
 type IDBValidKey = number | string | Date | BufferSource | IDBValidKey[];
diff --git a/baselines/ts5.6/dom.generated.d.ts b/baselines/ts5.6/dom.generated.d.ts
index 14a864267..053c4e930 100644
--- a/baselines/ts5.6/dom.generated.d.ts
+++ b/baselines/ts5.6/dom.generated.d.ts
@@ -10035,7 +10035,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/anchors)
      */
-    readonly anchors: HTMLCollectionOf<HTMLAnchorElement>;
+    readonly anchors: HTMLCollection<HTMLAnchorElement>;
     /**
      * The **`applets`** property of the Document returns an empty HTMLCollection.
      * @deprecated
@@ -10140,7 +10140,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/embeds)
      */
-    readonly embeds: HTMLCollectionOf<HTMLEmbedElement>;
+    readonly embeds: HTMLCollection<HTMLEmbedElement>;
     /**
      * **`fgColor`** gets/sets the foreground color, or text color, of the current document.
      * @deprecated
@@ -10153,7 +10153,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/forms)
      */
-    readonly forms: HTMLCollectionOf<HTMLFormElement>;
+    readonly forms: HTMLCollection<HTMLFormElement>;
     /**
      * The **`fragmentDirective`** read-only property of the Document interface returns the FragmentDirective for the current document.
      *
@@ -10190,7 +10190,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/images)
      */
-    readonly images: HTMLCollectionOf<HTMLImageElement>;
+    readonly images: HTMLCollection<HTMLImageElement>;
     /**
      * The **`Document.implementation`** property returns a A DOMImplementation object.
      *
@@ -10221,7 +10221,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/links)
      */
-    readonly links: HTMLCollectionOf<HTMLAnchorElement | HTMLAreaElement>;
+    readonly links: HTMLCollection<HTMLAnchorElement | HTMLAreaElement>;
     /**
      * The **`Document.location`** read-only property returns a and provides methods for changing that URL and loading another URL.
      *
@@ -10253,7 +10253,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/plugins)
      */
-    readonly plugins: HTMLCollectionOf<HTMLEmbedElement>;
+    readonly plugins: HTMLCollection<HTMLEmbedElement>;
     /**
      * The **`Document.readyState`** property describes the loading state of the document.
      *
@@ -10278,7 +10278,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/scripts)
      */
-    readonly scripts: HTMLCollectionOf<HTMLScriptElement>;
+    readonly scripts: HTMLCollection<HTMLScriptElement>;
     /**
      * The **`scrollingElement`** read-only property of the scrolls the document.
      *
@@ -10525,7 +10525,7 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/getElementsByClassName)
      */
-    getElementsByClassName(classNames: string): HTMLCollectionOf<Element>;
+    getElementsByClassName(classNames: string): HTMLCollection;
     /**
      * The **`getElementsByName()`** method of the Document object returns a NodeList Collection of elements with a given `name` attribute in the document.
      *
@@ -10537,21 +10537,21 @@ interface Document extends Node, DocumentOrShadowRoot, FontFaceSource, GlobalEve
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/getElementsByTagName)
      */
-    getElementsByTagName<K extends keyof HTMLElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<HTMLElementTagNameMap[K]>;
-    getElementsByTagName<K extends keyof SVGElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<SVGElementTagNameMap[K]>;
-    getElementsByTagName<K extends keyof MathMLElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<MathMLElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof HTMLElementTagNameMap>(qualifiedName: K): HTMLCollection<HTMLElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof SVGElementTagNameMap>(qualifiedName: K): HTMLCollection<SVGElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof MathMLElementTagNameMap>(qualifiedName: K): HTMLCollection<MathMLElementTagNameMap[K]>;
     /** @deprecated */
-    getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(qualifiedName: K): HTMLCollectionOf<HTMLElementDeprecatedTagNameMap[K]>;
-    getElementsByTagName(qualifiedName: string): HTMLCollectionOf<Element>;
+    getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(qualifiedName: K): HTMLCollection<HTMLElementDeprecatedTagNameMap[K]>;
+    getElementsByTagName(qualifiedName: string): HTMLCollection;
     /**
      * Returns a list of elements with the given tag name belonging to the given namespace.
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Document/getElementsByTagNameNS)
      */
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1999/xhtml", localName: string): HTMLCollectionOf<HTMLElement>;
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/2000/svg", localName: string): HTMLCollectionOf<SVGElement>;
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1998/Math/MathML", localName: string): HTMLCollectionOf<MathMLElement>;
-    getElementsByTagNameNS(namespace: string | null, localName: string): HTMLCollectionOf<Element>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1999/xhtml", localName: string): HTMLCollection<HTMLElement>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/2000/svg", localName: string): HTMLCollection<SVGElement>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1998/Math/MathML", localName: string): HTMLCollection<MathMLElement>;
+    getElementsByTagNameNS(namespace: string | null, localName: string): HTMLCollection;
     /**
      * The **`getSelection()`** method of the Document interface returns the Selection object associated with this document, representing the range of text selected by the user, or the current position of the caret.
      *
@@ -11159,27 +11159,27 @@ interface Element extends Node, ARIAMixin, Animatable, ChildNode, NonDocumentTyp
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Element/getElementsByClassName)
      */
-    getElementsByClassName(classNames: string): HTMLCollectionOf<Element>;
+    getElementsByClassName(classNames: string): HTMLCollection;
     /**
      * The **`Element.getElementsByTagName()`** method returns a live All descendants of the specified element are searched, but not the element itself.
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Element/getElementsByTagName)
      */
-    getElementsByTagName<K extends keyof HTMLElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<HTMLElementTagNameMap[K]>;
-    getElementsByTagName<K extends keyof SVGElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<SVGElementTagNameMap[K]>;
-    getElementsByTagName<K extends keyof MathMLElementTagNameMap>(qualifiedName: K): HTMLCollectionOf<MathMLElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof HTMLElementTagNameMap>(qualifiedName: K): HTMLCollection<HTMLElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof SVGElementTagNameMap>(qualifiedName: K): HTMLCollection<SVGElementTagNameMap[K]>;
+    getElementsByTagName<K extends keyof MathMLElementTagNameMap>(qualifiedName: K): HTMLCollection<MathMLElementTagNameMap[K]>;
     /** @deprecated */
-    getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(qualifiedName: K): HTMLCollectionOf<HTMLElementDeprecatedTagNameMap[K]>;
-    getElementsByTagName(qualifiedName: string): HTMLCollectionOf<Element>;
+    getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(qualifiedName: K): HTMLCollection<HTMLElementDeprecatedTagNameMap[K]>;
+    getElementsByTagName(qualifiedName: string): HTMLCollection;
     /**
      * The **`Element.getElementsByTagNameNS()`** method returns a live HTMLCollection of elements with the given tag name belonging to the given namespace.
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/Element/getElementsByTagNameNS)
      */
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1999/xhtml", localName: string): HTMLCollectionOf<HTMLElement>;
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/2000/svg", localName: string): HTMLCollectionOf<SVGElement>;
-    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1998/Math/MathML", localName: string): HTMLCollectionOf<MathMLElement>;
-    getElementsByTagNameNS(namespace: string | null, localName: string): HTMLCollectionOf<Element>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1999/xhtml", localName: string): HTMLCollection<HTMLElement>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/2000/svg", localName: string): HTMLCollection<SVGElement>;
+    getElementsByTagNameNS(namespaceURI: "http://www.w3.org/1998/Math/MathML", localName: string): HTMLCollection<MathMLElement>;
+    getElementsByTagNameNS(namespace: string | null, localName: string): HTMLCollection;
     /**
      * The **`getHTML()`** method of the Element interface is used to serialize an element's DOM to an HTML string.
      *
@@ -13688,7 +13688,7 @@ declare var HTMLCanvasElement: {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLCollection)
  */
-interface HTMLCollectionBase {
+interface HTMLCollectionBase<E extends Element = Element, N = never> {
     /**
      * The **`HTMLCollection.length`** property returns the number of items in a HTMLCollection.
      *
@@ -13700,17 +13700,17 @@ interface HTMLCollectionBase {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLCollection/item)
      */
-    item(index: number): Element | null;
-    [index: number]: Element;
+    item(index: number): E | null;
+    [index: number]: E;
 }
 
-interface HTMLCollection extends HTMLCollectionBase {
+interface HTMLCollection<E extends Element = Element, N = never> extends HTMLCollectionBase {
     /**
      * The **`namedItem()`** method of the HTMLCollection interface returns the first Element in the collection whose `id` or `name` attribute match the specified name, or `null` if no element matches.
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLCollection/namedItem)
      */
-    namedItem(name: string): Element | null;
+    namedItem(name: string): E | N | null;
 }
 
 declare var HTMLCollection: {
@@ -13718,12 +13718,6 @@ declare var HTMLCollection: {
     new(): HTMLCollection;
 };
 
-interface HTMLCollectionOf<T extends Element> extends HTMLCollectionBase {
-    item(index: number): T | null;
-    namedItem(name: string): T | null;
-    [index: number]: T;
-}
-
 /**
  * The **`HTMLDListElement`** interface provides special properties (beyond those of the regular HTMLElement interface it also has available to it by inheritance) for manipulating definition list (dl) elements.
  *
@@ -13782,7 +13776,7 @@ interface HTMLDataListElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLDataListElement/options)
      */
-    readonly options: HTMLCollectionOf<HTMLOptionElement>;
+    readonly options: HTMLCollection<HTMLOptionElement>;
     addEventListener<K extends keyof HTMLElementEventMap>(type: K, listener: (this: HTMLDataListElement, ev: HTMLElementEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;
     removeEventListener<K extends keyof HTMLElementEventMap>(type: K, listener: (this: HTMLDataListElement, ev: HTMLElementEventMap[K]) => any, options?: boolean | EventListenerOptions): void;
@@ -14284,7 +14278,7 @@ declare var HTMLFontElement: {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLFormControlsCollection)
  */
-interface HTMLFormControlsCollection extends HTMLCollectionBase {
+interface HTMLFormControlsCollection extends HTMLCollection<Element, RadioNodeList> {
     /**
      * The **`HTMLFormControlsCollection.namedItem()`** method returns the RadioNodeList or the Element in the collection whose `name` or `id` match the specified name, or `null` if no node matches.
      *
@@ -15522,7 +15516,7 @@ interface HTMLMapElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLMapElement/areas)
      */
-    readonly areas: HTMLCollection;
+    readonly areas: HTMLCollection<HTMLAreaElement>;
     /**
      * The **`name`** property of the HTMLMapElement represents the unique name `<map>` element.
      *
@@ -16296,7 +16290,7 @@ declare var HTMLOptionElement: {
  *
  * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLOptionsCollection)
  */
-interface HTMLOptionsCollection extends HTMLCollectionOf<HTMLOptionElement> {
+interface HTMLOptionsCollection extends HTMLCollection<HTMLOptionElement> {
     /**
      * The **`length`** property of the HTMLOptionsCollection interface returns the number of option elements in the collection.
      *
@@ -16752,7 +16746,7 @@ interface HTMLSelectElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLSelectElement/selectedOptions)
      */
-    readonly selectedOptions: HTMLCollectionOf<HTMLOptionElement>;
+    readonly selectedOptions: HTMLCollection<HTMLOptionElement>;
     /**
      * The **`size`** property of the HTMLSelectElement interface specifies the number of options, or rows, that should be visible at one time.
      *
@@ -17255,7 +17249,7 @@ interface HTMLTableElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLTableElement/rows)
      */
-    readonly rows: HTMLCollectionOf<HTMLTableRowElement>;
+    readonly rows: HTMLCollection<HTMLTableRowElement>;
     /**
      * The **`HTMLTableElement.rules`** property indicates which cell borders to render in the table.
      * @deprecated
@@ -17275,7 +17269,7 @@ interface HTMLTableElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLTableElement/tBodies)
      */
-    readonly tBodies: HTMLCollectionOf<HTMLTableSectionElement>;
+    readonly tBodies: HTMLCollection<HTMLTableSectionElement>;
     /**
      * The **`HTMLTableElement.tFoot`** property represents the `null` if there is no such element.
      *
@@ -17393,7 +17387,7 @@ interface HTMLTableRowElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLTableRowElement/cells)
      */
-    readonly cells: HTMLCollectionOf<HTMLTableCellElement>;
+    readonly cells: HTMLCollection<HTMLTableCellElement>;
     /**
      * The **`ch`** property of the HTMLTableRowElement interface does nothing.
      * @deprecated
@@ -17482,7 +17476,7 @@ interface HTMLTableSectionElement extends HTMLElement {
      *
      * [MDN Reference](https://developer.mozilla.org/docs/Web/API/HTMLTableSectionElement/rows)
      */
-    readonly rows: HTMLCollectionOf<HTMLTableRowElement>;
+    readonly rows: HTMLCollection<HTMLTableRowElement>;
     /**
      * The **`vAlign`** property of the HTMLTableSectionElement interface is a string indicating how to vertically align text in a thead, tbody or tfoot table section.
      * @deprecated
diff --git a/baselines/ts5.6/dom.iterable.generated.d.ts b/baselines/ts5.6/dom.iterable.generated.d.ts
index f26da3b31..688a76f01 100644
--- a/baselines/ts5.6/dom.iterable.generated.d.ts
+++ b/baselines/ts5.6/dom.iterable.generated.d.ts
@@ -146,14 +146,10 @@ interface HTMLAllCollection {
     [Symbol.iterator](): ArrayIterator<Element>;
 }
 
-interface HTMLCollectionBase {
+interface HTMLCollectionBase<E extends Element = Element, N = never> {
     [Symbol.iterator](): ArrayIterator<Element>;
 }
 
-interface HTMLCollectionOf<T extends Element> {
-    [Symbol.iterator](): ArrayIterator<T>;
-}
-
 interface HTMLFormElement {
     [Symbol.iterator](): ArrayIterator<Element>;
 }
diff --git a/baselines/ts5.6/serviceworker.generated.d.ts b/baselines/ts5.6/serviceworker.generated.d.ts
index 42749c941..1a68b35a1 100644
--- a/baselines/ts5.6/serviceworker.generated.d.ts
+++ b/baselines/ts5.6/serviceworker.generated.d.ts
@@ -11489,6 +11489,8 @@ type GLsizei = number;
 type GLsizeiptr = number;
 type GLuint = number;
 type GLuint64 = number;
+/** @deprecated */
+type HTMLCollectionOf<T extends Element> = HTMLCollection<T>;
 type HashAlgorithmIdentifier = AlgorithmIdentifier;
 type HeadersInit = [string, string][] | Record<string, string> | Headers;
 type IDBValidKey = number | string | Date | BufferSource | IDBValidKey[];
diff --git a/baselines/ts5.6/sharedworker.generated.d.ts b/baselines/ts5.6/sharedworker.generated.d.ts
index e1dd7e2be..827716a1a 100644
--- a/baselines/ts5.6/sharedworker.generated.d.ts
+++ b/baselines/ts5.6/sharedworker.generated.d.ts
@@ -11178,6 +11178,8 @@ type GLsizei = number;
 type GLsizeiptr = number;
 type GLuint = number;
 type GLuint64 = number;
+/** @deprecated */
+type HTMLCollectionOf<T extends Element> = HTMLCollection<T>;
 type HashAlgorithmIdentifier = AlgorithmIdentifier;
 type HeadersInit = [string, string][] | Record<string, string> | Headers;
 type IDBValidKey = number | string | Date | BufferSource | IDBValidKey[];
diff --git a/baselines/ts5.6/webworker.generated.d.ts b/baselines/ts5.6/webworker.generated.d.ts
index be3f9748b..6ab5bf35d 100644
--- a/baselines/ts5.6/webworker.generated.d.ts
+++ b/baselines/ts5.6/webworker.generated.d.ts
@@ -13146,6 +13146,8 @@ type GLsizei = number;
 type GLsizeiptr = number;
 type GLuint = number;
 type GLuint64 = number;
+/** @deprecated */
+type HTMLCollectionOf<T extends Element> = HTMLCollection<T>;
 type HashAlgorithmIdentifier = AlgorithmIdentifier;
 type HeadersInit = [string, string][] | Record<string, string> | Headers;
 type IDBValidKey = number | string | Date | BufferSource | IDBValidKey[];
diff --git a/baselines/webworker.generated.d.ts b/baselines/webworker.generated.d.ts
index b8a2a5c53..14d582beb 100644
--- a/baselines/webworker.generated.d.ts
+++ b/baselines/webworker.generated.d.ts
@@ -13146,6 +13146,8 @@ type GLsizei = number;
 type GLsizeiptr = number;
 type GLuint = number;
 type GLuint64 = number;
+/** @deprecated */
+type HTMLCollectionOf<T extends Element> = HTMLCollection<T>;
 type HashAlgorithmIdentifier = AlgorithmIdentifier;
 type HeadersInit = [string, string][] | Record<string, string> | Headers;
 type IDBValidKey = number | string | Date | BufferSource | IDBValidKey[];
diff --git a/inputfiles/addedTypes.jsonc b/inputfiles/addedTypes.jsonc
index fbc48d8dd..d7d4ae852 100644
--- a/inputfiles/addedTypes.jsonc
+++ b/inputfiles/addedTypes.jsonc
@@ -695,45 +695,6 @@
                     ]
                 }
             },
-            "HTMLCollectionOf": {
-                "name": "HTMLCollectionOf",
-                "typeParameters": [
-                    {
-                        "name": "T",
-                        "extends": "Element"
-                    }
-                ],
-                "exposed": "Window",
-                "extends": "HTMLCollection",
-                "methods": {
-                    "method": {
-                        "item": {
-                            "getter": true,
-                            "signature": [
-                                {
-                                    "nullable": true,
-                                    "overrideType": "T",
-                                    "param": [
-                                        {
-                                            "name": "index",
-                                            "type": "unsigned long"
-                                        }
-                                    ]
-                                }
-                            ],
-                            "specs": "html5",
-                            "name": "item"
-                        },
-                        "namedItem": {
-                            "name": "namedItem",
-                            "overrideSignatures": [
-                                "namedItem(name: string): T | null"
-                            ]
-                        }
-                    }
-                },
-                "noInterfaceObject": true
-            },
             "Element": {
                 "name": "Element",
                 "methods": {
@@ -742,7 +703,7 @@
                             "name": "getElementsByClassName",
                             "signature": {
                                 "0": {
-                                    "overrideType": "HTMLCollectionOf<Element>"
+                                    "overrideType": "HTMLCollection"
                                 }
                             }
                         },
@@ -1618,6 +1579,17 @@
                     }
                 ]
             },
+            {
+                "name": "HTMLCollectionOf",
+                "deprecated": true,
+                "typeParameters": [
+                    {
+                        "name": "T",
+                        "extends": "Element"
+                    }
+                ],
+                "overrideType": "HTMLCollection<T>"
+            },
             {
                 "name": "ReadableStreamReadResult",
                 "typeParameters": [
diff --git a/inputfiles/knownTypes.json b/inputfiles/knownTypes.json
index d0ba44099..9746c695f 100644
--- a/inputfiles/knownTypes.json
+++ b/inputfiles/knownTypes.json
@@ -83,6 +83,7 @@
         "HkdfParams",
         "HmacImportParams",
         "HmacKeyGenParams",
+        "HTMLCollectionOf",
         "ImageBitmapRenderingContextSettings",
         "NamedCurve",
         "Pbkdf2Params",
diff --git a/inputfiles/overridingTypes.jsonc b/inputfiles/overridingTypes.jsonc
index 8a5a30d30..11f025e6e 100644
--- a/inputfiles/overridingTypes.jsonc
+++ b/inputfiles/overridingTypes.jsonc
@@ -824,13 +824,13 @@
                         "getElementsByTagNameNS": {
                             "name": "getElementsByTagNameNS",
                             "additionalSignatures": [
-                                "getElementsByTagNameNS(namespaceURI: \"http://www.w3.org/1999/xhtml\", localName: string): HTMLCollectionOf<HTMLElement>",
-                                "getElementsByTagNameNS(namespaceURI: \"http://www.w3.org/2000/svg\", localName: string): HTMLCollectionOf<SVGElement>",
-                                "getElementsByTagNameNS(namespaceURI: \"http://www.w3.org/1998/Math/MathML\", localName: string): HTMLCollectionOf<MathMLElement>"
+                                "getElementsByTagNameNS(namespaceURI: \"http://www.w3.org/1999/xhtml\", localName: string): HTMLCollection<HTMLElement>",
+                                "getElementsByTagNameNS(namespaceURI: \"http://www.w3.org/2000/svg\", localName: string): HTMLCollection<SVGElement>",
+                                "getElementsByTagNameNS(namespaceURI: \"http://www.w3.org/1998/Math/MathML\", localName: string): HTMLCollection<MathMLElement>"
                             ],
                             "signature": {
                                 "0": {
-                                    "overrideType": "HTMLCollectionOf<Element>"
+                                    "overrideType": "HTMLCollection"
                                 }
                             }
                         },
@@ -838,7 +838,7 @@
                             "name": "getElementsByClassName",
                             "signature": {
                                 "0": {
-                                    "overrideType": "HTMLCollectionOf<Element>"
+                                    "overrideType": "HTMLCollection"
                                 }
                             }
                         },
@@ -874,31 +874,31 @@
                         },
                         "anchors": {
                             "name": "anchors",
-                            "overrideType": "HTMLCollectionOf<HTMLAnchorElement>"
+                            "overrideType": "HTMLCollection<HTMLAnchorElement>"
                         },
                         "embeds": {
                             "name": "embeds",
-                            "overrideType": "HTMLCollectionOf<HTMLEmbedElement>"
+                            "overrideType": "HTMLCollection<HTMLEmbedElement>"
                         },
                         "forms": {
                             "name": "forms",
-                            "overrideType": "HTMLCollectionOf<HTMLFormElement>"
+                            "overrideType": "HTMLCollection<HTMLFormElement>"
                         },
                         "images": {
                             "name": "images",
-                            "overrideType": "HTMLCollectionOf<HTMLImageElement>"
+                            "overrideType": "HTMLCollection<HTMLImageElement>"
                         },
                         "links": {
                             "name": "links",
-                            "overrideType": "HTMLCollectionOf<HTMLAnchorElement | HTMLAreaElement>"
+                            "overrideType": "HTMLCollection<HTMLAnchorElement | HTMLAreaElement>"
                         },
                         "plugins": {
                             "name": "plugins",
-                            "overrideType": "HTMLCollectionOf<HTMLEmbedElement>"
+                            "overrideType": "HTMLCollection<HTMLEmbedElement>"
                         },
                         "scripts": {
                             "name": "scripts",
-                            "overrideType": "HTMLCollectionOf<HTMLScriptElement>"
+                            "overrideType": "HTMLCollection<HTMLScriptElement>"
                         },
                         "location": {
                             // Pre-TS-5.1 hack to make document.location assignable
@@ -1506,7 +1506,7 @@
                         },
                         "selectedOptions": {
                             "name": "selectedOptions",
-                            "overrideType": "HTMLCollectionOf<HTMLOptionElement>"
+                            "overrideType": "HTMLCollection<HTMLOptionElement>"
                         },
                         "labels": {
                             "name": "labels",
@@ -1523,7 +1523,7 @@
                     "property": {
                         "options": {
                             "name": "options",
-                            "overrideType": "HTMLCollectionOf<HTMLOptionElement>"
+                            "overrideType": "HTMLCollection<HTMLOptionElement>"
                         }
                     }
                 }
@@ -1570,11 +1570,11 @@
                     "property": {
                         "rows": {
                             "name": "rows",
-                            "overrideType": "HTMLCollectionOf<HTMLTableRowElement>"
+                            "overrideType": "HTMLCollection<HTMLTableRowElement>"
                         },
                         "tBodies": {
                             "name": "tBodies",
-                            "overrideType": "HTMLCollectionOf<HTMLTableSectionElement>"
+                            "overrideType": "HTMLCollection<HTMLTableSectionElement>"
                         }
                     }
                 }
@@ -1584,7 +1584,7 @@
                     "property": {
                         "rows": {
                             "name": "rows",
-                            "overrideType": "HTMLCollectionOf<HTMLTableRowElement>"
+                            "overrideType": "HTMLCollection<HTMLTableRowElement>"
                         }
                     }
                 }
@@ -1595,13 +1595,13 @@
                         "getElementsByTagNameNS": {
                             "name": "getElementsByTagNameNS",
                             "additionalSignatures": [
-                                "getElementsByTagNameNS(namespaceURI: \"http://www.w3.org/1999/xhtml\", localName: string): HTMLCollectionOf<HTMLElement>",
-                                "getElementsByTagNameNS(namespaceURI: \"http://www.w3.org/2000/svg\", localName: string): HTMLCollectionOf<SVGElement>",
-                                "getElementsByTagNameNS(namespaceURI: \"http://www.w3.org/1998/Math/MathML\", localName: string): HTMLCollectionOf<MathMLElement>"
+                                "getElementsByTagNameNS(namespaceURI: \"http://www.w3.org/1999/xhtml\", localName: string): HTMLCollection<HTMLElement>",
+                                "getElementsByTagNameNS(namespaceURI: \"http://www.w3.org/2000/svg\", localName: string): HTMLCollection<SVGElement>",
+                                "getElementsByTagNameNS(namespaceURI: \"http://www.w3.org/1998/Math/MathML\", localName: string): HTMLCollection<MathMLElement>"
                             ],
                             "signature": {
                                 "0": {
-                                    "overrideType": "HTMLCollectionOf<Element>"
+                                    "overrideType": "HTMLCollection"
                                 }
                             }
                         }
@@ -1717,7 +1717,7 @@
                 ]
             },
             "HTMLOptionsCollection": {
-                "extends": "HTMLCollectionOf<HTMLOptionElement>"
+                "extends": "HTMLCollection<HTMLOptionElement>"
             },
             "SubtleCrypto": {
                 "methods": {
@@ -2137,7 +2137,7 @@
                     "property": {
                         "cells": {
                             "name": "cells",
-                            "overrideType": "HTMLCollectionOf<HTMLTableCellElement>"
+                            "overrideType": "HTMLCollection<HTMLTableCellElement>"
                         }
                     }
                 }
@@ -2567,6 +2567,16 @@
                     }
                 }
             },
+            "HTMLMapElement": {
+                "properties": {
+                    "property": {
+                        "areas": {
+                            "name": "areas",
+                            "overrideType": "HTMLCollection<HTMLAreaElement>"
+                        }
+                    }
+                }
+            },
             "HTMLMarqueeElement": {
                 "element": [
                     {
@@ -3550,6 +3560,39 @@
             "ContactAddress": {
                 "name": "PaymentAddress"
             },
+            "HTMLCollection": {
+                "typeParameters": [
+                    {
+                        "name": "E",
+                        "extends": "Element",
+                        "default": "Element"
+                    },
+                    {
+                        "name": "N",
+                        "default": "never"
+                    }
+                ],
+                "methods": {
+                    "method": {
+                        "item": {
+                            "overrideSignatures": [
+                                "item(index: number): E | null"
+                            ]
+                        },
+                        "namedItem": {
+                            "overrideSignatures": [
+                                "namedItem(name: string): E | N | null"
+                            ]
+                        }
+                    }
+                },
+                "overrideIndexSignatures": [
+                    "[index: number]: E"
+                ]
+            },
+            "HTMLFormControlsCollection": {
+                "extends": "HTMLCollection<Element, RadioNodeList>"
+            },
             "HTMLMediaElement": {
                 "properties": {
                     "property": {
diff --git a/src/build/emitter.ts b/src/build/emitter.ts
index 14189ed17..f19c8cc4f 100644
--- a/src/build/emitter.ts
+++ b/src/build/emitter.ts
@@ -600,15 +600,15 @@ export function emitWebIdl(
       const paramName = m.signature[0].param![0].name;
       for (const mapName of tagNameMapNames) {
         printer.printLine(
-          `getElementsByTagName<K extends keyof ${mapName}>(${paramName}: K): HTMLCollectionOf<${mapName}[K]>;`,
+          `getElementsByTagName<K extends keyof ${mapName}>(${paramName}: K): HTMLCollection<${mapName}[K]>;`,
         );
       }
       printer.printLine("/** @deprecated */");
       printer.printLine(
-        `getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(${paramName}: K): HTMLCollectionOf<HTMLElementDeprecatedTagNameMap[K]>;`,
+        `getElementsByTagName<K extends keyof HTMLElementDeprecatedTagNameMap>(${paramName}: K): HTMLCollection<HTMLElementDeprecatedTagNameMap[K]>;`,
       );
       printer.printLine(
-        `getElementsByTagName(${paramName}: string): HTMLCollectionOf<Element>;`,
+        `getElementsByTagName(${paramName}: string): HTMLCollection;`,
       );
     }
   }