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.

There are 3 kinds of attributes that you can add to your HTML tags: Element-specific, global, and event handler content attributes.

The <script> element accepts the following attributes.

Element-Specific Attributes

This table shows the attributes that are specific to the <script> tag/element.

AttributeDescription
srcSpecifies a URI/URL of an external script.
asyncSpecifies 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 async or async="async").

Possible values:

  • [Empty string]
  • async
deferSpecifies 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 defer or defer="defer").

Possible values:

  • [Empty string]
  • defer
typeSpecifies the scripting language as a content-type (MIME type).
charsetDefines the character encoding that the script uses.
crossoriginThis 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:

ValueDescription
anonymousCross-origin CORS requests for the element will not have the credentials flag set. In other words, there will be no exchange of user credentials via cookies, client-side SSL certificates or HTTP authentication.
use-credentialsCross-origin CORS requests for the element will have the credentials flag set.

If this attribute is not specified, CORS is not used at all.

An invalid keyword and an empty string will be handled as the anonymous value.

Global Attributes

The following attributes are standard across all HTML5 elements. Therefore, you can use these attributes with the <script> tag , as well as with all other HTML tags.

For a full explanation of these attributes, see HTML 5 global attributes.

Event Handler Content Attributes

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.

Below are the standard HTML5 event handler content attributes.

Again, you can use any of these with the <script> element, as well as any other HTML5 element.

For a full explanation of these attributes, see HTML 5 event handler content attributes.

Differences Between HTML 4 & HTML 5

HTML5 does not support the language attribute, which is deprecated in HTML 4.

HTML5 introduced the following attributes:

The type attribute is a required attribute in HTML 4 but it is optional in HTML5. Also, in HTML 4 there is no default value for this attribute. In HTML5, the default value is text/javascript.

To see more detail on the two versions see HTML5 <script> Tag and HTML4 <script> Tag. Also check out the links to the official specifications below.

Template

Here's a template for the <script> tag with all available attributes for the tag (based on HTML5). These are grouped into attribute types, each type separated by a space. In many cases, you will probably only need one or two (if any) attributes. Simply remove the attributes you don't need.

For more information on attributes for this tag, see HTML5 <script> Tag and HTML4 <script> Tag.

Tag Details

For more details about the <script> tag, see HTML5 <script> Tag and HTML4 <script> Tag.

Specifications

Here are the official specifications for the <script> element.

What's the Difference?

W3C creates "snapshot" specifications that don't change once defined. So the HTML5 specification won't change once it becomes an official recommendation. WHATWG on the other hand, develops a "living standard" that is updated on a regular basis. In general, you will probably find that the HTML living standard will be more closely aligned to the current W3C draft than to the HTML5 specification.

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