diff --git a/src/htmlLanguageTypes.ts b/src/htmlLanguageTypes.ts
index fd75c7e..e87e334 100644
--- a/src/htmlLanguageTypes.ts
+++ b/src/htmlLanguageTypes.ts
@@ -84,6 +84,12 @@ export interface Node {
 	children: Node[];
 	parent?: Node;
 	attributes?: { [name: string]: string | null } | undefined;
+	/**
+	 * Returns true if this is a `<script type="module">` node.
+	 * Module scripts have isolated scopes per the HTML specification,
+	 * unlike classic scripts which share a global scope.
+	 */
+	readonly isModule: boolean;
 }
 
 export enum TokenType {
diff --git a/src/parser/htmlParser.ts b/src/parser/htmlParser.ts
index 652e7ac..ab071bc 100644
--- a/src/parser/htmlParser.ts
+++ b/src/parser/htmlParser.ts
@@ -15,6 +15,18 @@ export class Node {
 	public endTagStart: number | undefined;
 	public attributes: { [name: string]: string | null } | undefined;
 	public get attributeNames(): string[] { return this.attributes ? Object.keys(this.attributes) : []; }
+	public get isModule(): boolean {
+		if (this.tag !== 'script') {
+			return false;
+		}
+		const type = this.attributes?.type;
+		if (!type) {
+			return false;
+		}
+		// Attribute values are stored with surrounding quotes (e.g., '"module"' or "'module'")
+		const unquoted = type.replace(/^['"]|['"]$/g, '');
+		return unquoted === 'module';
+	}
 	constructor(public start: number, public end: number, public children: Node[], public parent?: Node) {
 	}
 	public isSameTag(tagInLowerCase: string | undefined) {
diff --git a/src/test/parser.test.ts b/src/test/parser.test.ts
index f4fbf0e..aea59d1 100644
--- a/src/test/parser.test.ts
+++ b/src/test/parser.test.ts
@@ -130,4 +130,36 @@ suite('HTML Parser', () => {
 			children: []
 		}]);
 	});
+
+	test('Script isModule', () => {
+		// Module scripts have isolated scopes (issue #133)
+		const doc1 = parse('<script type="module">let a = 0;</script>');
+		assert.strictEqual(doc1.roots[0].isModule, true);
+
+		// Classic scripts share the global scope
+		const doc2 = parse('<script>let a = 0;</script>');
+		assert.strictEqual(doc2.roots[0].isModule, false);
+
+		// Single-quoted attribute value
+		const doc3 = parse("<script type='module'>let a = 0;</script>");
+		assert.strictEqual(doc3.roots[0].isModule, true);
+
+		// Other type values are not modules
+		const doc4 = parse('<script type="text/javascript">let a = 0;</script>');
+		assert.strictEqual(doc4.roots[0].isModule, false);
+
+		// Non-script tags are not modules
+		const doc5 = parse('<div type="module"></div>');
+		assert.strictEqual(doc5.roots[0].isModule, false);
+
+		// Multiple scripts: module scripts have isolated scopes
+		const doc6 = parse('<script type="module">let a = 0;</script><script type="module">let a = 0;</script>');
+		assert.strictEqual(doc6.roots[0].isModule, true);
+		assert.strictEqual(doc6.roots[1].isModule, true);
+
+		// Mixed: module and classic scripts
+		const doc7 = parse('<script type="module">let a = 0;</script><script>let a = 0;</script>');
+		assert.strictEqual(doc7.roots[0].isModule, true);
+		assert.strictEqual(doc7.roots[1].isModule, false);
+	});
 });