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).
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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 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 | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Basic support | Chrome Full support Yes | Edge Full support Yes | 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 | Edge Mobile 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.