Web/HTML/Element/script

The HTML <script> element is used to embed executable code or data; this is typically used to embed or refer to JavaScript code. The <script> element can also be used with other languages, such as WebGL's GLSL shader programming language and JSON.

Content categories	Metadata content, Flow content, Phrasing content.
Permitted content	Dynamic script such as `text/javascript`.
Tag omission	None, both the starting and ending tag are mandatory.
Permitted parents	Any element that accepts metadata content, or any element that accepts phrasing content.
Implicit ARIA role	No corresponding role
Permitted ARIA roles	No `role` permitted
DOM interface	`HTMLScriptElement`

Attributes

This element includes the global attributes.

asyncHTML5

For classic scripts, if the async attribute is present, then the classic script will be fetched in parallel to parsing and evaluated as soon as it is available.

For module scripts, if the async attribute is present then the scripts and all their dependencies will be executed in the defer queue, therefore they will get fetched in parallel to parsing and evaluated as soon as they are available.

This attribute allows the elimination of parser-blocking JavaScript where the browser would have to load and evaluate scripts before continuing to parse. defer has a similar effect in this case.

This is a boolean attribute: the presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.

See Browser compatibility for notes on browser support. See also Async scripts for asm.js.

crossorigin

Normal script elements pass minimal information to the window.onerror for scripts which do not pass the standard CORS checks. To allow error logging for sites which use a separate domain for static media, use this attribute. See CORS settings attributes for a more descriptive explanation of its valid arguments.

defer

This Boolean attribute is set to indicate to a browser that the script is meant to be executed after the document has been parsed, but before firing DOMContentLoaded.

Scripts with the defer attribute will prevent the DOMContentLoaded event from firing until the script has loaded and finished evaluating.

This attribute must not be used if the src attribute is absent (i.e. for inline scripts), in this case it would have no effect.

The defer attribute has no effect on module scripts — they defer by default.

Scripts with the defer attribute will execute in the order in which they appear in the document.

This attribute allows the elimination of parser-blocking JavaScript where the browser would have to load and evaluate scripts before continuing to parse. async has a similar effect in this case.

integrity

This attribute contains inline metadata that a user agent can use to verify that a fetched resource has been delivered free of unexpected manipulation. See Subresource Integrity.

nomodule

This Boolean attribute is set to indicate that the script should not be executed in browsers that support ES2015 modules — in effect, this can be used to serve fallback scripts to older browsers that do not support modular JavaScript code.

nonce

A cryptographic nonce (number used once) to whitelist scripts in a script-src Content-Security-Policy. The server must generate a unique nonce value each time it transmits a policy. It is critical to provide a nonce that cannot be guessed as bypassing a resource's policy is otherwise trivial.

referrerpolicy

Indicates which referrer to send when fetching the script, or resources fetched by the script:

no-referrer: The Referer header will not be sent.
no-referrer-when-downgrade (default): The Referer header will not be sent to origins without TLS (HTTPS).
origin: The sent referrer will be limited to the origin of the referring page: its scheme, host, and port.
origin-when-cross-origin: The referrer sent to other origins will be limited to the scheme, the host, and the port. Navigations on the same origin will still include the path.
same-origin: A referrer will be sent for same origin, but cross-origin requests will contain no referrer information.
strict-origin: Only send the origin of the document as the referrer when the protocol security level stays the same (e.g. HTTPS→HTTPS), but don't send it to a less secure destination (e.g. HTTPS→HTTP).
strict-origin-when-cross-origin: Send a full URL when performing a same-origin request, but only send the origin when the protocol security level stays the same (e.g.HTTPS→HTTPS), and send no header to a less secure destination (e.g. HTTPS→HTTP).
unsafe-url: The referrer will include the origin and the path (but not the fragment, password, or username). This value is unsafe, because it leaks origins and paths from TLS-protected resources to insecure origins.

Note: An empty string value ("") is both the default value, and a fallback value if referrerpolicy is not supported. If referrerpolicy is not explicitly specified on the <script> element, it will adopt a higher-level referrer policy, i.e. one set on the whole document or domain. If a higher-level policy is not available, the empty string is treated as being equivalent to no-referrer-when-downgrade.

src

This attribute specifies the URI of an external script; this can be used as an alternative to embedding a script directly within a document.

type

This attribute indicates the type of script represented. The value of this attribute will be in one of the following categories:

Omitted or a JavaScript MIME type: This indicates the script is JavaScript. The HTML5 specification urges authors to omit the attribute rather than provide a redundant MIME type. In earlier browsers, this identified the scripting language of the embedded or imported (via the src attribute) code. JavaScript MIME types are listed in the specification.
module: Causes the code to be treated as a JavaScript module. The processing of the script contents is not affected by the charset and defer attributes. For information on using module, see our JavaScript modules guide. Unlike classic scripts, module scripts require the use of the CORS protocol for cross-origin fetching.
Any other value: The embedded content is treated as a data block which won't be processed by the browser. Developers must use a valid MIME type that is not a JavaScript MIME type to denote data blocks. The src attribute will be ignored.

Deprecated attributes

charset ': If present, its value must be an ASCII case-insensitive match for "utf-8". It’s unnecessary to specify the charset attribute, because documents must use UTF-8, and the script element inherits its character encoding from the document.
language ': Like the type attribute, this attribute identifies the scripting language in use. Unlike the type attribute, however, this attribute’s possible values were never standardized. The type attribute should be used instead.

Notes

Scripts without async , defer or type="module" attributes, as well as inline scripts, are fetched and executed immediately, before the browser continues to parse the page.

The script should be served with the text/javascript MIME type, but browsers are lenient and only block them if the script is served with an image type (image/*); a video type (video/*); an audio (audio/*) type; or text/csv. If the script is blocked, an error is sent to the element, if not a load event is sent.

Examples

Basic usage

These examples show how to import (an external) script using the <script> element.

<script src="javascript.js"></script>

And the following examples show how to put (an inline) script inside the <script> element.

<script>
  alert("Hello World!");
</script>

Module fallback

Browsers that support the module value for the type attribute ignore any script with a nomodule attribute. That enables you to use module scripts while also providing nomodule-marked fallback scripts for non-supporting browsers.

<script type="module" src="main.js"></script>
<script nomodule src="fallback.js"></script>

Embedding data in HTML

You can also use the <script> element to embed data in HTML with server-side rendering by specifying a valid non-JavaScript MIME type in the type attribute.

<!-- Generated by the server -->
<script id="data" type="application/json">{"userId":1234,"userName":"John Doe","memberSince":"2000-01-01T00:00:00.000Z"}</script>

<!-- Static -->
<script>
  const userInfo = JSON.parse(document.getElementById("data").text);
  console.log("User information: %o", userInfo);
</script>

Specifications

Specification	Status	Comments
HTML Living StandardThe definition of '<script>' in that specification.	Living Standard	Removed the `charset` attribute
HTML5The definition of '<script>' in that specification.	Recommendation
HTML 4.01 SpecificationThe definition of '<script>' in that specification.	Recommendation

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`script`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1 Notes' Full support 1 Notes' Notes' Starting in Firefox 4, inserting <script> elements that have been created by calling `document.createElement("script")` no longer enforces execution in insertion order. This change lets Firefox properly abide by the specification. To make script-inserted external scripts execute in their insertion order, set `.async=false` on them.	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
`async`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
`crossorigin`	Chrome Full support 30	Edge Full support ≤18	Firefox Full support 13	IE No support No	Opera Full support 12	Safari Full support Yes Notes' Full support Yes Notes' Notes' The `crossorigin` attribute was implemented in WebKit in WebKit bug 81438.	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 14	Opera Android ?	Safari iOS ?	Samsung Internet Android Full support Yes
`defer`	Chrome Full support Yes Notes' Full support Yes Notes' Notes' Chrome does not defer scripts with the `defer` attribute when the page is served as XHTML (`application/xhtml+xml`) - Chromium Issue #611136, Chromium Issue #874749	Edge Full support 12	Firefox Full support 3.5 Notes' Full support 3.5 Notes' Notes' Since Firefox 3.6, the `defer` attribute is ignored on scripts that don't have the `src` attribute. However, in Firefox 3.5 even inline scripts are deferred if the `defer` attribute is set.	IE Full support 10 Notes' Full support 10 Notes' Notes' In versions prior to Internet Explorer 10, it implemented `defer` by a proprietary specification. Since version 10 it conforms to the W3C specification.	Opera Full support Yes Notes' Full support Yes Notes' Notes' Opera does not defer scripts with the `defer` attribute when the page is served as XHTML (`application/xhtml+xml`) - Chromium Issue #611136, Chromium Issue #874749	Safari Full support Yes	WebView Android Full support Yes Notes' Full support Yes Notes' Notes' WebView does not defer scripts with the `defer` attribute when the page is served as XHTML (`application/xhtml+xml`) - Chromium Issue #611136, Chromium Issue #874749	Chrome Android Full support Yes Notes' Full support Yes Notes' Notes' Chrome does not defer scripts with the `defer` attribute when the page is served as XHTML (`application/xhtml+xml`) - Chromium Issue #611136, Chromium Issue #874749	Firefox Android Full support 4	Opera Android Full support Yes Notes' Full support Yes Notes' Notes' Opera does not defer scripts with the `defer` attribute when the page is served as XHTML (`application/xhtml+xml`) - Chromium Issue #611136, Chromium Issue #874749	Safari iOS Full support Yes	Samsung Internet Android Full support Yes Notes' Full support Yes Notes' Notes' Samsung Internet does not defer scripts with the `defer` attribute when the page is served as XHTML (`application/xhtml+xml`) - Chromium Issue #611136, Chromium Issue #874749
`integrity`	Chrome Full support 45	Edge Partial support 17	Firefox Full support 43	IE No support No	Opera Full support Yes	Safari Full support Yes	WebView Android Full support 45	Chrome Android Full support 45	Firefox Android Full support 43	Opera Android ?	Safari iOS No support No	Samsung Internet Android Full support 5.0
`language` Deprecated'Non-standard'	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
`nomodule` Experimental'	Chrome Full support 61	Edge Full support 16	Firefox Full support 60 Full support 60 No support 55 — 60 Disabled' Disabled' From version 55 until version 60 (exclusive): this feature is behind the `dom.moduleScripts.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera Full support 48	Safari Full support 11	WebView Android Full support 61	Chrome Android Full support 61	Firefox Android Full support 60 Full support 60 No support 55 — 60 Disabled' Disabled' From version 55 until version 60 (exclusive): this feature is behind the `dom.moduleScripts.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android Full support 45	Safari iOS Full support 11	Samsung Internet Android Full support 8.0
`referrerPolicy`	Chrome Full support 70	Edge Full support ≤79	Firefox Full support 65	IE No support No	Opera Full support Yes	Safari No support No	WebView Android Full support 70	Chrome Android Full support 70	Firefox Android Full support 65	Opera Android ?	Safari iOS No support No	Samsung Internet Android Full support 10.0
`src`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
`text`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
`type`	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support 4	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes
`type.module`	Chrome Full support 61	Edge Full support 16	Firefox Full support 60 Full support 60 No support 54 — 60 Disabled' Disabled' From version 54 until version 60 (exclusive): this feature is behind the `dom.moduleScripts.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera Full support 48	Safari Full support 10.1	WebView Android Full support 61	Chrome Android Full support 61	Firefox Android Full support 60 Full support 60 No support 54 — 60 Disabled' Disabled' From version 54 until version 60 (exclusive): this feature is behind the `dom.moduleScripts.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android Full support 45	Safari iOS Full support 10.3	Samsung Internet Android Full support 8.0
`type`: The `version` parameter of the `type` attribute Non-standard'	Chrome No support No	Edge No support No	Firefox No support ? — 59	IE No support No	Opera No support No	Safari No support No	WebView Android No support No	Chrome Android No support No	Firefox Android No support ? — 59	Opera Android No support No	Safari iOS No support No	Samsung Internet Android No support No

Legend

Full support: Full support
Partial support: Partial support
No support: No support
Compatibility unknown: Compatibility unknown
Experimental. Expect behavior to change in the future.': Experimental. Expect behavior to change in the future.
Non-standard. Expect poor cross-browser support.': Non-standard. Expect poor cross-browser support.
Deprecated. Not for use in new websites.': Deprecated. Not for use in new websites.
See implementation notes.': See implementation notes.
User must explicitly enable this feature.': User must explicitly enable this feature.

Compatibility notes

In older browsers that don't support the async attribute, parser-inserted scripts block the parser; script-inserted scripts execute asynchronously in IE and WebKit, but synchronously in Opera and pre-4 Firefox. In Firefox 4, the async DOM property defaults to true for script-created scripts, so the default behaviour matches the behaviour of IE and WebKit.

To request script-inserted external scripts be executed in the insertion order in browsers where the document.createElement("script").async evaluates to true (such as Firefox 4), set async="false" on the scripts you want to maintain order.

Never call document.write() from an async script. In Firefox 3.6, calling document.write() has an unpredictable effect. In Firefox 4, calling document.write() from an async script has no effect (other than printing a warning to the error console).