The id global attribute defines an 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).
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This attribute's value is an opaque string: this means that web authors should not rely on it to convey human-readable information (although having your IDs somewhat human-readable can be useful for code comprehension, e.g. consider ticket-18659 versus r45tgfe-freds&$@).
id'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 value.
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 HTML5, 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 of 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
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
id | Chrome Full support Yes | Edge Full support 12 | Firefox
Full support
32
| IE Full support Yes | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Firefox Android
Full support
32
| Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes |
Legend
- Full support
- Full support
- See implementation notes.
- See implementation notes.
See also
- All global attributes.
Element.idthat reflects this attribute.