diff --git a/src/storage/sanitizeTag.js b/src/storage/sanitizeTag.js
new file mode 100644
index 0000000..ac5a10e
--- /dev/null
+++ b/src/storage/sanitizeTag.js
@@ -0,0 +1,44 @@
+/**
+ * Sanitizes a snapshot tag into a safe filename.
+ *
+ * Only allows A-Z, a-z, 0-9, '.', '_', and '-'.
+ * All other characters are replaced with '_'.
+ *
+ * This prevents:
+ * - Path traversal attacks via '../' or '..\'
+ * - Invalid filename characters on Windows (e.g. ':', '*', '?', '"', '<', '>', '|')
+ * - Accidental subdirectory creation via '/' or '\'
+ *
+ * @param {string} tag - The raw snapshot tag from user input.
+ * @returns {string} A sanitized tag safe for use as a filename.
+ */
+export function sanitizeTag(tag) {
+  if (typeof tag !== "string" || tag.length === 0) {
+    return "untitled";
+  }
+
+  // Replace any character that is NOT alphanumeric, dot, underscore, or hyphen
+  let sanitized = tag.replace(/[^A-Za-z0-9._-]/g, "_");
+
+  // Collapse consecutive underscores (e.g. "foo___bar" -> "foo_bar")
+  sanitized = sanitized.replace(/_+/g, "_");
+
+  // Strip leading/trailing underscores and dots for safety
+  sanitized = sanitized.replace(/^[_\.]+|[_\.]+$/g, "");
+
+  // Replace any remaining '..' sequences (path traversal) with '_'
+  sanitized = sanitized.replace(/\.\./g, "_");
+
+  // Collapse any new consecutive underscores from the '..' replacement
+  sanitized = sanitized.replace(/_+/g, "_");
+
+  // Strip again after '..' replacement
+  sanitized = sanitized.replace(/^[_\.]+|[_\.]+$/g, "");
+
+  // Final safety: if sanitization produced an empty string, return a default
+  if (sanitized.length === 0) {
+    return "untitled";
+  }
+
+  return sanitized;
+}
diff --git a/src/storage/snapshotStore.js b/src/storage/snapshotStore.js
index 0af020d..0b624a6 100644
--- a/src/storage/snapshotStore.js
+++ b/src/storage/snapshotStore.js
@@ -1,6 +1,7 @@
 import fs from "fs";
 import path from "path";
 import os from "os";
+import { sanitizeTag } from "./sanitizeTag.js";
 
 // Stores globally in ~/.apidrift/snapshots/
 const SNAP_DIR = path.join(os.homedir(), ".apidrift", "snapshots");
@@ -8,13 +9,15 @@ const SNAP_DIR = path.join(os.homedir(), ".apidrift", "snapshots");
 if (!fs.existsSync(SNAP_DIR)) fs.mkdirSync(SNAP_DIR, { recursive: true });
 
 export function saveSnapshot(tag, data) {
-  const file = path.join(SNAP_DIR, `${tag}.json`);
+  const safeTag = sanitizeTag(tag);
+  const file = path.join(SNAP_DIR, `${safeTag}.json`);
   fs.writeFileSync(file, JSON.stringify(data, null, 2));
   return file;
 }
 
 export function loadSnapshot(tag) {
-  const file = path.join(SNAP_DIR, `${tag}.json`);
+  const safeTag = sanitizeTag(tag);
+  const file = path.join(SNAP_DIR, `${safeTag}.json`);
   if (!fs.existsSync(file)) {
     console.error(`Snapshot "${tag}" not found. Run: apidrift list`);
     process.exit(1);
diff --git a/tests/core/sanitizeTag.test.js b/tests/core/sanitizeTag.test.js
new file mode 100644
index 0000000..e6f2e99
--- /dev/null
+++ b/tests/core/sanitizeTag.test.js
@@ -0,0 +1,68 @@
+import { sanitizeTag } from "../../src/storage/sanitizeTag.js";
+
+describe("sanitizeTag", () => {
+  it("passes through safe tags unchanged", () => {
+    expect(sanitizeTag("v1.0")).toBe("v1.0");
+    expect(sanitizeTag("v1.0.13")).toBe("v1.0.13");
+    expect(sanitizeTag("prod-users")).toBe("prod-users");
+    expect(sanitizeTag("my_snapshot")).toBe("my_snapshot");
+    expect(sanitizeTag("abc123")).toBe("abc123");
+  });
+
+  it("replaces colons with underscores", () => {
+    expect(sanitizeTag("v1:0:0")).toBe("v1_0_0");
+    expect(sanitizeTag("2026-05-19T12:00:00")).toBe("2026-05-19T12_00_00");
+  });
+
+  it("prevents path traversal via ../", () => {
+    expect(sanitizeTag("../etc/passwd")).toBe("etc_passwd");
+    expect(sanitizeTag("..\\windows\\system32")).toBe("windows_system32");
+    expect(sanitizeTag("foo/../../bar")).toBe("foo_bar");
+  });
+
+  it("blocks path separators", () => {
+    expect(sanitizeTag("foo/bar")).toBe("foo_bar");
+    expect(sanitizeTag("foo\\bar")).toBe("foo_bar");
+  });
+
+  it("handles Windows-invalid characters", () => {
+    expect(sanitizeTag("con:nul")).toBe("con_nul");
+    expect(sanitizeTag("file?.json")).toBe("file_.json");
+    expect(sanitizeTag("star*test")).toBe("star_test");
+    expect(sanitizeTag('quote"test')).toBe("quote_test");
+    expect(sanitizeTag("less<than")).toBe("less_than");
+    expect(sanitizeTag("greater>than")).toBe("greater_than");
+    expect(sanitizeTag("pipe|test")).toBe("pipe_test");
+  });
+
+  it("handles empty and invalid input", () => {
+    expect(sanitizeTag("")).toBe("untitled");
+    expect(sanitizeTag(null)).toBe("untitled");
+    expect(sanitizeTag(undefined)).toBe("untitled");
+    expect(sanitizeTag(123)).toBe("untitled");
+  });
+
+  it("handles tags that are entirely unsafe characters", () => {
+    expect(sanitizeTag("../../")).toBe("untitled");
+    expect(sanitizeTag("...")).toBe("untitled");
+    expect(sanitizeTag("///")).toBe("untitled");
+    expect(sanitizeTag("   ")).toBe("untitled");
+  });
+
+  it("collapses consecutive unsafe replacements", () => {
+    expect(sanitizeTag("foo   bar")).toBe("foo_bar");
+    expect(sanitizeTag("a//b//c")).toBe("a_b_c");
+    expect(sanitizeTag("x:y:z")).toBe("x_y_z");
+  });
+
+  it("strips leading and trailing underscores from sanitization", () => {
+    expect(sanitizeTag("/foo")).toBe("foo");
+    expect(sanitizeTag("foo/")).toBe("foo");
+    expect(sanitizeTag(":v1.0:")).toBe("v1.0");
+  });
+
+  it("preserves dots, underscores, and hyphens in the middle", () => {
+    expect(sanitizeTag("my-app_v2.1.0-beta")).toBe("my-app_v2.1.0-beta");
+    expect(sanitizeTag("a.b_c-d")).toBe("a.b_c-d");
+  });
+});