Nothing kills the momentum of picking a new username like reaching the sign-up screen and getting “this username isn’t allowed.” Every platform enforces its own rules for length and characters, and they are rarely the same twice. This guide collects the essentials so you can choose a handle that will actually be accepted. Rules do change, so always confirm on the platform itself before you commit.
Instagram usernames can contain letters, numbers, periods, and underscores — no spaces, no other symbols. The limit is 30 characters, though most people stay far shorter. Usernames are not case-sensitive, so capital letters in your handle are stored as lowercase. Note that your username (the @handle) is separate from your display name, which can include spaces, emoji, and other characters. When you are ready to build one, the Instagram username generator keeps every suggestion within these limits automatically.
TikTok
TikTok usernames also allow letters, numbers, underscores, and periods, up to 24 characters. You cannot end a username with a period, and TikTok requires that a handle not be purely numeric. Like Instagram, TikTok separates the unique username from the display nickname. If your Instagram handle is free here too, grab it — matching handles make you far easier to follow across apps. The TikTok username generator is tuned to these constraints.
Discord
Discord moved to a new username system built around unique, lowercase handles. Usernames use lowercase letters, numbers, periods, and underscores, and must be between 2 and 32 characters. You cannot use two periods or underscores in a row, and some words are reserved. Separately, each server lets you set a display nickname with far looser rules. The Discord username generator produces handles that fit the lowercase format.
Roblox
Roblox is one of the stricter platforms. Usernames are 3 to 20 characters, can include letters, numbers, and a single underscore (but not at the start or end), and no other symbols or spaces. Roblox also filters names for anything resembling personal information or inappropriate content. Because the rules are tight, it helps to generate ideas that already fit — the Roblox username generator does exactly that.
YouTube
YouTube handles (the @name that appears on your channel URL) are 3 to 30 characters and can include letters, numbers, underscores, periods, and hyphens. Handles cannot look like a URL or phone number. Your channel name — the larger display name — is separate and far more flexible. The YouTube username generator helps you find a handle that fits the format and matches your brand.
Why the differences matter
These inconsistencies are exactly why a name that is perfect on one app fails on another. A handle with a hyphen works on YouTube but not on Instagram. A mixed-case tag looks fine until Discord lowercases it. A three-character name is fine on Roblox but might be reserved elsewhere. If you want one consistent identity, you have to choose within the intersection of all your platforms’ rules — the strictest common denominator.
A quick strategy
Pick your primary platform and design your username around its rules first, keeping it short, lowercase-safe, and free of exotic symbols. A handle that is 4 to 15 lowercase letters and numbers with at most one separator will pass on almost every major platform. Then test that exact handle everywhere before committing.
Once you have a shortlist, verify availability on each service — our guide on how to check if a username is available walks through the fastest method for each platform. And if you want help generating options that respect these limits from the start, browse the platform-specific tools linked throughout this post. Getting the character rules right up front means you only fall in love with usernames you can actually claim.