files/en-us/glossary/identifier/index.md
An identifier is a sequence of characters in the code that identifies a {{glossary("variable")}}, {{glossary("function")}}, or {{glossary("property")}}. In most languages, identifiers are case-sensitive and not quoted.
In {{glossary("JavaScript")}}, identifiers can contain {{glossary("Unicode")}} letters, $, _, and digits (0-9), but may not start with a digit. An identifier differs from a string in that a {{glossary("string")}} is data, while an identifier is part of the code. In JavaScript, there is no way to convert identifiers to strings, but sometimes it is possible to parse strings into identifiers.
In {{glossary("CSS")}}, there are two identifier data types: {{cssxref("custom-ident")}} and {{cssxref("dashed-ident")}}. The CSS {{cssxref("ident")}} can contain almost any character, but non-letter/digit ASCII characters such as ", \, and * must be escaped, it must not start with a digit, and emojis are valid as identifiers that do not require escaping.