The HTML <script> element is used to embed or reference executable code; 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.

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.
Permitted ARIA roles None
DOM interface HTMLScriptElement


This element includes the global attributes.

This is a Boolean attribute indicating that the browser should, if possible, execute the script asynchronously.

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

Browsers usually assume the worst case scenario and load scripts synchronously, (i.e. async=false) during HTML parsing.

Dynamically inserted scripts (using document.createElement) execute asynchronously by default, so to turn on synchronous execution (i.e. scripts execute in the order they were inserted) set async=false.

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

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.
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.

To achieve a similar effect for dynamically inserted scripts use async=false instead. Scripts with the defer attribute will execute in the order in which they appear in the document.
Indicates the relative importance of the script. Priority hints are delegated using the values:

auto: Indicates no preference. The browser may use its own heuristics to decide the priority of the script.

high: Indicates to the browser that the script is of high priority.

low: Indicates to the browser that the script is of low priority.

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.
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.
A cryptographic nonce (number used once) to whitelist inline 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.
This attribute specifies the URI of an external script; this can be used as an alternative to embedding a script directly within a document.

If a script element has a src attribute specified, it should not have a script embedded inside its tags.

Like the textContent attribute, this attribute sets the text content of the element. Unlike the textContent attribute, however, this attribute is evaluated as executable code after the node is inserted into the DOM.

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: For HTML5-compliant browsers this indicates the script is JavaScript. 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: HTML5 For HTML5-compliant browsers the code is 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 ES6 in Depth: Modules. Code may behave differently when the module keyword is used.
  • 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.

Note: in Firefox you could specify the version of JavaScript contained in a <script> element by including a non-standard version parameter inside the type attribute — for example type="text/javascript;version=1.8". This has been removed in Firefox 59 (see bug 1428745).

Deprecated attributes

If present, its value must be an ASCII case-insensitive match for "utf-8". Both 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.
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.


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.



These examples show how to import script using the <script> element in both HTML4 and HTML5.

<!-- HTML4 -->
<script type="text/javascript" src="javascript.js"></script>

<!-- HTML5 -->
<script src="javascript.js"></script>

Module Fallback

Browsers that support module for the type attribute ignore scripts with a nomodule attribute. This provides a way to use a module with a fallback for non-supporting browsers.

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


Specification Status Comments
HTML Living Standard
The definition of '<script>' in that specification.
Living Standard Removed the charset attribute
The definition of '<script>' in that specification.
Unknown Removed the charset attribute
HTML 5.2
The definition of '<script>' in that specification.
Recommendation Adds the module type
HTML 5.1
The definition of '<script>' in that specification.
The definition of '<script>' in that specification.
HTML 4.01 Specification
The definition of '<script>' in that specification.
Subresource Integrity
The definition of '<script>' in that specification.
Recommendation Adds the integrity attribute.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support1 Yes11 Yes Yes Yes
async1 Yes1 Yes Yes Yes
crossorigin30 Yes13 No12 Yes2
defer Yes3 Yes3.54105 No Yes
integrity45 No43 No ? No6
language1 Yes1 Yes Yes Yes
nomodule Yes No


55 — 607

No No No
src1 Yes1 Yes Yes Yes
text1 Yes1 Yes Yes Yes
type1 Yes1 Yes Yes Yes


54 — 608

type: The version parameter of the type attribute No No Yes — 59 No No No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes Yes4 Yes Yes Yes
async Yes Yes Yes4 Yes Yes Yes
crossorigin Yes Yes ?14 ? ? Yes
defer Yes Yes Yes4 ? Yes Yes
integrity4545 No43 ? No5.0
language Yes Yes Yes4 Yes Yes Yes
nomodule Yes Yes No


55 — 607

? No Yes
src Yes Yes Yes4 Yes Yes Yes
text Yes Yes Yes4 Yes Yes Yes
type Yes Yes Yes4 Yes Yes Yes


54 — 608

4810.3 No
type: The version parameter of the type attribute No No No Yes — 59 No No No

1. 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.

2. The crossorigin attribute was implemented in WebKit in WebKit bug 81438.

3. 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

4. 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.

5. In versions prior to Internet Explorer 10, it implemented defer by a proprietary specification. Since version 10 it conforms to the W3C specification.

6. WebKit bug 148363 tracks WebKit implementation of Subresource Integrity (which includes the integrity attribute).

7. 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.

8. 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.

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).

See also