Web/CSS/ident

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The <ident> CSS data type denotes an arbitrary string used as an identifier.

Syntax

The syntax of <custom-ident> is similar to CSS identifiers (such as property names), except that it is case-sensitive. It consists of one or more characters, where characters can be any of the following:

any alphabetical character (A to Z, or a to z),
any decimal digit (0 to 9),
a hyphen (-),
an underscore (_),
an escaped character (preceded by a backslash, \),
a Unicode character (in the format of a backslash, \, followed by one to six hexadecimal digits, representing its Unicode code point)

Note that id1, Id1, iD1 and ID1 are all different identifiers as they are case-sensitive. On the other hand, as there are several ways to escape a character, toto\? and toto\3F are the same identifiers.

Examples

Valid identifiers

nono79       A mix of alphanumeric characters and numbers
ground-level    A mix of alphanumeric characters and a dash
-test           A dash followed by alphanumeric characters
--toto          A custom-property like identifier
_internal       An underscore followed by alphanumeric characters
\22 toto        A Unicode character followed by a sequence of alphanumeric characters
bili\.bob       A correctly escaped period

Invalid identifiers

34rem      It must not start with a decimal digit.
-12rad      It must not start with a dash followed by a decimal digit.
bili.bob    Only alphanumeric characters, _, and - needn't be escaped.
'bilibob'   This would be a <string>.
"bilibob"   This would be a <string>.

Specifications

Specification	Status	Comment
CSS Values and Units Module Level 4The definition of '`<ident>`' in that specification.	Editor's Draft
CSS Values and Units Module Level 3The definition of '`<ident>`' in that specification.	Candidate Recommendation

Browser compatibility

As this type is not a real type but a convenience type used to simplify the definition of other CSS syntax.