Roblox username format checker
Check length, allowed characters and underscore placement before trying a name on Roblox. This tool runs in your browser and checks text format only.
What this check can tell you
A username must have 3–20 characters, use letters and digits, and contain at most one underscore inside the name. For example, Moon_Otter has a valid format; _MoonOtter starts with an underscore and fails this check. Neither example has been checked for availability.
Roblox Support: username format guidance. Reference checked October 6, 2026.
What Roblox still needs to decide
Roblox checks whether the username is already in use and whether it passes moderation. A local format pass cannot answer either question. Confirm your final choice in Roblox’s own account flow.