The maximum length of a Twitter username was 15 characters before the X rebrand.
Usernames, also called handles, identify accounts in profile URLs, mentions, replies, and direct messages. They were separate from display names, which could be longer and could include spaces. A handle commonly began with the @ symbol, although the symbol was not technically part of the username itself.
The limit helped keep mentions compact and was especially important when Twitter posts had a 140-character limit. It also made handles suitable for older mobile interfaces and SMS-based interactions. Display names and usernames are often confused: changing a display name does not change the account’s handle or profile address.
After Elon Musk’s acquisition and Twitter’s 2023 rebrand as X, account naming rules and verification policies changed in several ways, but the historic 15-character limit remains a commonly cited fact about Twitter’s original identity system.