diff --git a/src/core/main.js b/src/core/main.js
index 0e19d75ec1..831735ece9 100644
--- a/src/core/main.js
+++ b/src/core/main.js
@@ -867,6 +867,23 @@ class p5 {
 
 // This is a pointer to our global mode p5 instance, if we're in
 // global mode.
+/**
+ * A variable that stores a reference to the sketch's p5 instance.
+ *
+ * In global mode, `p5.instance` refers to the sketch's p5 instance. It's
+ * useful when a function or method needs a reference to the sketch. For
+ * example, it can be used with
+ * <a href="#/p5.Shader/copyToContext">copyToContext()</a> to copy a
+ * <a href="#/p5.Shader">p5.Shader</a> object from a
+ * <a href="#/p5.Graphics">p5.Graphics</a> object to the main canvas.
+ *
+ * Note: `p5.instance` is only available in global mode. In instance mode,
+ * use the instance variable instead.
+ *
+ * @property {p5} instance
+ * @for p5
+ * @readOnly
+ */
 p5.instance = null;
 
 /**
diff --git a/src/webgl/p5.Shader.js b/src/webgl/p5.Shader.js
index a82f112361..18af8d78a2 100644
--- a/src/webgl/p5.Shader.js
+++ b/src/webgl/p5.Shader.js
@@ -587,7 +587,7 @@ p5.Shader = class {
    * <a href="#/p5.Graphics">p5.Graphics</a>, as in
    * `myShader.copyToContext(pg)`. The shader can also be copied from a
    * <a href="#/p5.Graphics">p5.Graphics</a> object to the main canvas using
-   * the `window` variable, as in `myShader.copyToContext(window)`.
+   * <a href="#/p5/instance">p5.instance</a>, as in `myShader.copyToContext(p5.instance)`.
    *
    * Note: A <a href="#/p5.Shader">p5.Shader</a> object created with
    * <a href="#/p5/createShader">createShader()</a>,
@@ -729,7 +729,7 @@ p5.Shader = class {
    *   pg.shader(original);
    *
    *   // Copy the original shader to the main canvas.
-   *   copied = original.copyToContext(window);
+   *   copied = original.copyToContext(p5.instance);
    *
    *   // Apply the copied shader to the main canvas.
    *   shader(copied);