In Unicode, the main emoji specification is Unicode Technical Standard #51, abbreviated UTS #51.
The standard is titled “Unicode Emoji” and defines the structure of emoji characters and sequences. It documents properties such as which characters count as emoji, whether they normally appear in text or emoji presentation, how skin-tone modifiers work, and how sequences using variation selectors or zero-width joiners are formed.
UTS #51 is maintained by the Unicode Consortium and is updated alongside Unicode releases, although its revisions can have their own publication schedule. As of September 2026, the current listed specification is version 18.0. The document also publishes supporting emoji data files used by software developers and font makers.
The number is easy to confuse with other Unicode standards. UTS #46 concerns Internationalized Domain Names, UTS #18 covers Unicode regular expressions, and UTS #10 defines the Unicode Collation Algorithm. Those are genuine Unicode standards, but they are not the main specification for emoji.