Username-with-only-letters-numbers-and-underscore

200+ TikTok Username Ideas (and how to pick one)

Nicknames Can Only Contain Alphanumeric Characters And Underscores - Catalog Library

Mistake in help text - should be underscore NOT hyphens · Issue #20 · backdrop-contrib/fanciblock · GitHub

Manage Users

Usernames can only use letters numbers underscores and periods

Fix Instagram Username can Only Use Letters, Numbers, Underscore, and Periods Problem Solved

General Banter — Vanilla Forums

Username, Roblox Wiki

UUKI Community Platform Blog