Username Rules Compared
Character limits and allowed symbols for the platforms people ask about most. These rules come from each platform's help pages and sign-up behaviour as of 2026; platforms change them occasionally, so the sign-up screen always has the final say.
| Platform | Length | Allowed characters | Other rules | Changing it |
|---|---|---|---|---|
| 1–30 | Letters, numbers, period, underscore | No two periods in a row; can't end with a period | Any time (old name can be reclaimed by you for about 14 days) | |
| TikTok | 2–24 | Letters, numbers, period, underscore | Can't end with a period | Once every 30 days |
| X (Twitter) | 4–15 | Letters, numbers, underscore | No periods or hyphens | Any time |
| YouTube handle | 3–30 | Letters, numbers, period, underscore, hyphen | Symbols can't be first or last | In YouTube Studio; changes are limited within a 14-day window |
| Twitch | 4–25 | Letters, numbers, underscore | Can't start with an underscore | Once every 60 days |
| Discord | 2–32 | Lowercase letters, numbers, period, underscore | No two periods in a row; no more #1234 tags | In User Settings (rate-limited) |
| Snapchat | 3–15 | Letters, numbers and one of - _ . | Must start with a letter; can't end with a symbol | Once a year |
| 3–20 | Letters, numbers, underscore, hyphen | — | Cannot be changed | |
| Roblox | 3–20 | Letters, numbers, one underscore | Underscore can't be first or last | Costs 1,000 Robux (display name is free to change) |
| GitHub | 1–39 | Letters, numbers, hyphen | No double hyphens; can't start or end with a hyphen | Any time (old links redirect until someone claims the name) |
| LinkedIn URL | 3–100 | Letters and numbers | No spaces, symbols or special characters | Any time in Edit public profile & URL |
Want to test a name against all of these at once? Use the username checker.
The One Username That Works Everywhere
If you want a single handle across every platform above, these constraints combine into a simple rule:
Platform Notes
Instagram and TikTok
Both allow periods and underscores, which makes them the most flexible for aesthetic handles like moon.diary. TikTok limits name changes to once every 30 days, so decide before you start posting.
X (Twitter)
The 4–15 character range and the ban on periods make X the hardest platform for long or dotted names. Check X first if consistency matters to you.
Discord
Since 2023, Discord usernames are lowercase and unique, with no #1234 discriminator. Capitals, spaces and symbols belong in your display name instead. See the Discord username generator.
Roblox
Roblox allows a single underscore that can't be first or last, and changing your username costs Robux, so choose carefully. Ideas on the Roblox username page.
Reddit usernames are permanent. If you want a new name you need a new account, which is another reason to use a name that doesn't reveal personal details.
Frequently Asked Questions
Which platform has the shortest username limit?
Among the big platforms, X (Twitter) and Snapchat both cap usernames at 15 characters. If you want the same handle everywhere, keep it to 15 characters or fewer and use only letters, numbers and underscores.
Which characters work on every platform?
Lowercase letters and numbers work everywhere. Underscores work almost everywhere (not in GitHub or LinkedIn URLs); periods do not work on X, Twitch or Roblox.
Are usernames case-sensitive?
On the platforms listed here, no: capital letters are either converted to lowercase or ignored when matching, so JaneDoe and janedoe are the same username.
What is the difference between a username and a display name?
The username (handle) is unique, appears in your profile URL and @mentions, and follows strict rules. The display name is the friendly name shown on your profile; on most platforms it can contain spaces and emojis and does not need to be unique.