Web/JavaScript/Reference/Global objects/Symbol/toStringTag

The Symbol.toStringTag well-known symbol is a string valued property that is used in the creation of the default string description of an object. It is accessed internally by the Object.prototype.toString() method.

Property attributes of `Symbol.toStringTag`
Writable	no
Enumerable	no
Configurable	no

Examples

Default tags

Object.prototype.toString.call('foo');     // "[object String]"
Object.prototype.toString.call([1, 2]);    // "[object Array]"
Object.prototype.toString.call(3);         // "[object Number]"
Object.prototype.toString.call(true);      // "[object Boolean]"
Object.prototype.toString.call(undefined); // "[object Undefined]"
Object.prototype.toString.call(null);      // "[object Null]"
// ... and more

Built-in toStringTag symbols

Object.prototype.toString.call(new Map());       // "[object Map]"
Object.prototype.toString.call(function* () {}); // "[object GeneratorFunction]"
Object.prototype.toString.call(Promise.resolve()); // "[object Promise]"
// ... and more

Custom classes default to object tag

When creating your own class, JavaScript defaults to the "Object" tag:

class ValidatorClass {}

Object.prototype.toString.call(new ValidatorClass()); // "[object Object]"

Custom tag with toStringTag

Now, with the help of toStringTag, you are able to set your own custom tag:

class ValidatorClass {
  get [Symbol.toStringTag]() {
    return 'Validator';
  }
}

Object.prototype.toString.call(new ValidatorClass()); // "[object Validator]"

toStringTag available on all DOM prototype objects

Due to a WebIDL spec change in mid-2020, browsers are adding a Symbol.toStringTag property to all DOM prototype objects. For example, to acccess the Symbol.toStringTag property on HTMLButtonElement:

let test = document.createElement('button');
test.toString(); // Returns [object HTMLButtonElement]
test[Symbol.toStringTag];  // Returns HTMLButtonElement

Specifications

Specification
ECMAScript (ECMA-262)The definition of 'Symbol.toStringTag' in that specification.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`toStringTag`	Chrome Full support 49	Edge Full support 15	Firefox Full support 51	IE No support No	Opera Full support 36	Safari Full support 10	WebView Android Full support 49	Chrome Android Full support 49	Firefox Android Full support 51	Opera Android Full support 36	Safari iOS Full support 10	Samsung Internet Android Full support 5.0	nodejs Full support 6.0.0 Full support 6.0.0 Full support 4.0.0 Disabled' Disabled' From version 4.0.0: this feature is behind the `--harmony` runtime flag.
`toStringTag` available on all DOM prototype objects	Chrome Full support 50	Edge Full support 79	Firefox Full support 78	IE No support No	Opera Full support 37	Safari Full support 14	WebView Android Full support 50	Chrome Android Full support 50	Firefox Android No support No	Opera Android Full support 37	Safari iOS Full support 14	Samsung Internet Android Full support 5.0	nodejs No support No

Legend

Full support: Full support
No support: No support
User must explicitly enable this feature.': User must explicitly enable this feature.