The id global attribute defines a unique identifier (ID) which must be unique in the whole document. Its purpose is to identify the element when linking (using a fragment identifier), scripting, or styling (with CSS).

This attribute's value is an opaque string: this means that web author must not use it to convey any information. Particular meaning, for example semantic meaning, must not be derived from the string.

This attribute's value must not contain whitespace (spaces, tabs etc.). Browsers treat non-conforming IDs that contain whitespace as if the whitespace is part of the ID. In contrast to the class attribute, which allows space-separated values, elements can only have one single ID.

Note: Using characters except ASCII letters, digits, '_', '-' and '.' may cause compatibility problems, as they weren't allowed in HTML 4. Though this restriction has been lifted in HTML 5, an ID should start with a letter for compatibility.

Specifications

Specification Status Comment
HTML Living Standard
The definition of 'id' in that specification.
Living Standard No change from latest snapshot, HTML 5.1
HTML 5.1
The definition of 'id' in that specification.
Recommendation Snapshot of HTML Living Standard, no change from HTML5
HTML5
The definition of 'id' in that specification.
Recommendation Snapshot of HTML Living Standard, now accept '_', '-' and '.' if not at the beginning fo the id. It is also a true global attribute.
HTML 4.01 Specification
The definition of 'id' in that specification.
Recommendation Supported on all elements but <base>, <head>, <html>, <meta>, <script>, <style>, and <title>.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes Yes

32

Yes — 321

Yes Yes Yes
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support Yes Yes Yes

32

Yes — 321

Yes Yes Yes

1. id is a true global attribute only since Firefox 32.

See also

Document Tags and Contributors

Contributors to this page: wbamberg, fscholz, auramgold, Ms2ger, markg, Sebastianz, teoli
Last updated by: wbamberg,