HTML <script> Tag
The HTML <script> tag is used for declaring a script within your HTML document.
Many web pages use scripts (usually JavaScript) to provide extra functionality that cannot be accomplished with HTML alone. Any time a script is embedded into an HTML document, it must be enclosed within <script> tags.
Syntax
The <script> tag is written as <script></script> with the script inserted between the start and end tags.
Like this:
Examples
Basic tag usage
Using the <noscript> Tag
You can use the <noscript> tag to provide content for user agents/browsers that don't support scripting.
Any content enclosed between the <noscript> tags is only displayed on browsers that don't support scripting.
Attributes
Attributes can be added to an HTML element to provide more information about how the element should appear or behave.
The <script> element accepts the following attributes.
| Attribute | Description | ||||||
|---|---|---|---|---|---|---|---|
src | Specifies a URI/URL of an external script. | ||||||
async | Specifies whether a script will executed asynchronously, as soon as it is available.
This is a boolean attribute. If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace (i.e. either Possible values:
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defer | Specifies whether the script is executed after the page has finished parsing, or immediately. If the async attribute is not present but the defer attribute is present, then the script is executed when the page has finished parsing. If neither attribute is present, then the script is fetched and executed immediately, before the user agent continues parsing the page.
This is a boolean attribute. If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace (i.e. either Possible values:
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type | Specifies the scripting language as a content-type (MIME type). Modern JavaScript is usually written without this attribute, since text/javascript is the default. One important exception is type="module", which treats the script as a JavaScript module rather than a classic script — module scripts are deferred by default, run in strict mode, and require CORS for cross-origin fetches. |
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nomodule | This is a boolean attribute. If present, the script is not executed in browsers that support JavaScript modules. This lets you provide a fallback script (without type="module") for older browsers, alongside a type="module" version for browsers that support it. |
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charset | Defines the character encoding that the script uses. This is unnecessary in practice today, since documents should use UTF-8 throughout, and the <script> element inherits its encoding from the document. |
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crossorigin | This attribute is a CORS settings attribute. CORS stands for Cross-Origin Resource Sharing. The purpose of the crossorigin attribute is to allow you to configure the CORS requests for the element's fetched data. The values for the crossorigin attribute are enumerated.
Possible values:
If this attribute is not specified, CORS is not used at all. An invalid keyword and an empty string will be handled as the |
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integrity | Contains a base64-encoded cryptographic hash of the external script, which the browser can use to verify the fetched file hasn't been tampered with (Subresource Integrity). Only valid when src is specified, and not valid on module scripts. |
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referrerpolicy | Indicates which referrer to send when fetching the script, and for any fetches the script itself makes, e.g. no-referrer or strict-origin-when-cross-origin. |
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fetchpriority | Provides a hint to the browser about the relative priority to use when fetching the script, compared to other scripts.
Possible values:
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Global Attributes
The following attributes are standard across all HTML elements. Therefore, you can use these attributes with the <script> tag , as well as with all other HTML tags.
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For a full explanation of these attributes, see HTML 5 global attributes.
Event Handlers
Event handler content attributes enable you to invoke a script from within your HTML. The script is invoked when a certain "event" occurs. Each event handler content attribute deals with a different event.
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Most event handler content attributes can be used on all HTML elements, but some event handlers have specific rules around when they can be used and which elements they are applicable to.
For more detail, see HTML event handler content attributes.