The<ident>CSSdata type denotes an arbitrary string used as anidentifier.

Syntax

A CSS identifier consists of one or more characters, which can be any of the following:

• anyASCII character in the rangesA-Z anda-z
• any decimal digit (0 to9)
• a hyphen (-)
• an underscore (_)
• any otherUnicode characterU+00A0 and higher (that is, any other non-ASCII Unicode character)
• anescaped character

Additionally, an identifier must not start with an unescaped digit, and must not start with an unescaped hyphen followed by an unescaped digit.

Note thatid1,Id1,iD1 andID1 are all different identifiers because they arecase-sensitive. On the other hand, since there are several ways to escape a character,toto\? andtoto\3F are the same identifiers.

Escaping characters

Escaping a character means representing it in a way that changes how it is interpreted by a software system. In CSS, you can escape a character by adding a backslash (\) in front of the character. Any character, except the hexadecimal digits0-9,a-f, andA-F, can be escaped in this way. For example,& can be escaped as\&.

You can also escape any character with a backslash followed by the character'sUnicodecode point represented by one to six hexadecimal digits. For example,& can be escaped as\26. In this usage, if the escaped character is followed by a hexadecimal digit, do one of the following:

• Place a space or other whitespace character after the Unicode code point.
• Provide the full six-digit Unicode code point of the character being escaped.

For example, the string&123 can be escaped as\26 123 (with a whitespace) or\000026123 (with the six-digit Unicode code point for&) to ensure that123 is not considered as part of the escape pattern.

Examples

Valid identifiers

nono79        /* A mix of alphanumeric characters and numbers */ground-level  /* A mix of alphanumeric characters and a dash */-test         /* A hyphen followed by alphanumeric characters */--toto        /* A custom-property like identifier */_internal     /* An underscore followed by alphanumeric characters */\22 toto      /* An escaped character followed by alphanumeric characters */\000022toto   /* Same as the previous example */scooby\.doo   /* A correctly escaped period */🔥123         /* A non-ASCII character followed by numbers */

Invalid identifiers

34rem     /* Must not start with a decimal digit */-12rad    /* Must not start with a dash followed by a decimal digit */scooby.doo  /* ASCII characters apart from alphanumerics must be escaped */'scoobyDoo' /* Treated as a string */"scoobyDoo" /* Treated as a string */

Specifications

Browser compatibility

As this type is not a real type but a convenience type used to simplify the definition of other CSS syntax, there is no browser compatibility information as such.

See also

• <custom-ident>
• <dashed-ident>