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

Attributes

This element includes the global attributes.

asyncHTML5

This is a Boolean attribute indicating that the browser should, if possible, load 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()) load asynchronously by default, so to turn on synchronous loading (i.e. scripts load in the order they were inserted) set async="false".

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.

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.

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 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.
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.

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

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.
  • 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

charset
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.
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 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 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>

Specifications

Specification Status Comments
HTML Living Standard
The definition of '<script>' in that specification.
Living Standard Removed the charset attribute
Unknown
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.
Recommendation  
HTML5
The definition of '<script>' in that specification.
Recommendation  
HTML 4.01 Specification
The definition of '<script>' in that specification.
Recommendation  
Subresource Integrity
The definition of '<script>' in that specification.
Recommendation Adds the integrity attribute.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
scriptChrome Full support 1Edge Full support YesFirefox 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 YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes
asyncChrome Full support 1Edge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes
crossoriginChrome Full support 30Edge Full support YesFirefox Full support 13IE No support NoOpera Full support 12Safari Full support Yes
Notes
Full support Yes
Notes
Notes The crossorigin attribute was implemented in WebKit in WebKit bug 81438.
WebView Android Full support YesChrome Android Full support YesEdge Mobile ? Firefox Android Full support 14Opera Android ? Safari iOS ? Samsung Internet Android Full support Yes
deferChrome 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 YesFirefox 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 No support NoSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android ? Safari iOS Full support YesSamsung Internet Android Full support Yes
integrityChrome Full support 45Edge Partial support 17Firefox Full support 43IE No support NoOpera Full support YesSafari Full support YesWebView Android Full support 45Chrome Android Full support 45Edge Mobile No support NoFirefox Android Full support 43Opera Android ? Safari iOS No support NoSamsung Internet Android Full support 5.0
language
DeprecatedNon-standard
Chrome Full support 1Edge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes
nomodule
Experimental
Chrome Full support 61Edge Full support 16Firefox 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 NoOpera Full support 48Safari Full support 11WebView Android Full support 61Chrome Android Full support 61Edge Mobile No support NoFirefox 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 45Safari iOS Full support 11Samsung Internet Android Full support Yes
referrerPolicyChrome Full support 70Edge ? Firefox Full support 65IE No support NoOpera Full support YesSafari No support NoWebView Android Full support 70Chrome Android Full support 70Edge Mobile ? Firefox Android Full support 65Opera Android ? Safari iOS No support NoSamsung Internet Android ?
srcChrome Full support 1Edge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes
textChrome Full support 1Edge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes
typeChrome Full support 1Edge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes
type.moduleChrome Full support 61Edge Full support 16Firefox 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 NoOpera Full support 48Safari Full support 10.1WebView Android Full support 61Chrome Android Full support 61Edge Mobile No support NoFirefox 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 45Safari iOS Full support 10.3Samsung Internet Android No support No
type: The version parameter of the type attribute
Non-standard
Chrome No support NoEdge No support NoFirefox No support ? — 59IE No support NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoEdge Mobile No support NoFirefox Android No support ? — 59Opera Android No support NoSafari iOS No support NoSamsung 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).

See also