A Roblox username is 3 to 20 characters, uses only a-z, A-Z, 0-9 and the underscore, and may contain at most one underscore, which cannot be the first or last character. No spaces, no dots, no hyphens, no emoji, no Cyrillic. Your display name is the separate, free, changeable-once-a-week name people actually see; it is also 3 to 20 characters but does allow single spaces between words. Changing the username itself costs Robux, and your old usernames stay findable afterwards.
The exact rules, in Roblox's own words
Every line below is the message Roblox's own validation service returns when a name breaks that rule, checked live on 5 September 2026.
| Rule | What Roblox answers when you break it |
|---|---|
| Length 3-20 characters | Usernames can be 3 to 20 characters long |
Only Latin letters, digits and _ |
Only a-z, A-Z, 0-9, and _ are allowed |
| At most one underscore | Usernames can have at most one _ |
| Underscore not at the start or end | Username can't start or end with _ |
| Must be unique | Username is already in use |
The length bounds are inclusive: a 3-character name passes, a 20-character name passes, 21 does not. There is no separate "no numbers at the start" rule — 123abc is a perfectly valid shape, it is just usually taken.
What gets rejected, with examples
| Attempt | Result | Reason |
|---|---|---|
ab |
Rejected | Under 3 characters |
Frost_Byte |
Valid shape | One underscore, in the middle |
Frost__Byte |
Rejected | Two underscores |
_FrostByte |
Rejected | Underscore at the start |
FrostByte_ |
Rejected | Underscore at the end |
Frost.Byte |
Rejected | Dot is not an allowed character |
Frost-Byte |
Rejected | Hyphen is not an allowed character |
Frost Byte |
Rejected | Space is not an allowed character |
Хорошо12 |
Rejected | Non-Latin characters |
This is the part that surprises people coming from Discord or Free Fire: on Roblox there is no symbol layer at all. Decorative frames, Japanese kaomoji and Unicode fonts do not fail the moderation filter — they fail the character check before moderation ever sees them.
Username vs display name
Roblox splits identity into two names, and almost every "how do I get a cool Roblox name" question is really about the second one.
| Username | Display name | |
|---|---|---|
| Length | 3-20 | 3-20 |
| Allowed characters | a-z A-Z 0-9 _ |
Latin letters, digits, underscore, single spaces |
| Spaces | No | Yes, one between words (double spaces and a leading space are rejected) |
| Unique | Yes | No — other players may have the same one |
| Cost to change | Robux | Free |
| How often | Any time you pay | Once every 7 days |
| Visible as | @username under your display name |
The name shown in experiences and on your profile |
Display names have their own validator, and it is stricter than people assume. Checked live on the same day:
| Attempt | Result |
|---|---|
Cool Name |
Accepted — one space between words |
Nice_Name |
Accepted |
Cool Name |
Rejected — a double space counts as an invalid character |
Cool |
Rejected — a leading space counts as an invalid character |
Cool-Name |
Rejected — no hyphens here either |
Ник2026 |
Rejected — invalid characters |
★star |
Rejected — invalid characters |
So the gain over a username is exactly one thing: you may separate words with a single space. That is enough to turn FrostByte7 into Frost Byte, and it is why the display name is the one worth thinking about.
Two details from Roblox's own display name article are worth keeping: a display name that breaks the Community Rules or Terms of Use "may be reset to your Username", and Japanese character support exists as a beta for some accounts, with more character support planned. That beta is the single exception to "Latin only", and you should not count on having it.
The filter
Roblox filters text continuously across the platform — chat, usernames and display names alike — against its Community Standards. Two practical consequences:
- A name that passes the character rules can still be refused or later reset if moderation reads it as inappropriate. Passing the validator is not approval.
- The filter is applied on a per-account basis with age in mind, so a name your friend uses is not a guarantee that yours will survive.
There is no published list of blocked words, and hunting for one is the wrong instinct. Pick something that reads cleanly out loud and move on.
How to change your username
The steps from Roblox Support:
- Log in, and open account Settings — the gear icon in the top right on the web, or the three-dot More menu in the mobile apps.
- Open the Account Info tab.
- Press Change Username (the pencil icon).
- Enter the new username, then your current password.
- Press Buy.
You sign in with the new username and the same password afterwards.
What a name change does not do
Roblox is explicit about the limits, and they are the part people find out too late:
- Old usernames remain visible in your Settings, on your Profile and through People search. Other players can look them up.
- You cannot take a name that belongs to another account, and you cannot swap names with your own alt.
- There is no discount for a trivial change — capitalising a letter costs the same as a whole new name.
- The original account creation date carries over, so a rename does not make the account look new.
- Changing back to an old username still costs Robux.
The help article says each change requires Robux but does not name the amount; the figure appears at the Buy step. Read it there before you confirm.
Picking a name that actually passes
The constraint is tight enough that trial and error is slow: most short, readable names have been taken since roughly 2008. A workable order of operations:
- Write the name you want with no symbols at all.
- If it is taken, extend it rather than decorating it — a word pair, a suffix, or a number that means something.
- Use the one allowed underscore as the only separator.
- Keep it under 20 characters so it is not truncated visually in feeds.
Our Roblox username generator builds names against those exact rules, so what it hands you cannot fail on characters or length — only on being taken. If you want the same handle across platforms, the gamertag generator checks the length limits of several services at once, and the Discord name generator follows Discord's own narrower a-z 0-9 . _ rule.
One honest warning about the fancy fonts you have seen on other games: the fancy text generator produces Unicode styles that Roblox usernames will reject outright, and display names too. Use them where they work — Discord display names, bios, profiles on other platforms — and keep your Roblox name plain.
Testing a name without spending Robux
The validation happens before the payment. Type the name you want into the Change Username field and the site runs it through the same length, character and availability rules listed above before it ever gets you to the Buy button. A rejection on any of those costs you nothing.
Check availability from the other direction too: old usernames stay in People search, so a name can be sitting on an account that has not been used in years. You cannot swap with it and you cannot free it — the rule that you cannot use a name belonging to another account applies to abandoned accounts as well.
If you lost the name
Recovery goes through the account, not the name: on the login page choose Forgot Username or Password, then enter your verified email or your phone number, and Roblox returns the usernames attached to it. A purchase receipt sometimes contains the username too. Roblox states plainly that without an email, phone number or purchase history there is no way to recover the account — which is the best argument there is for adding both before you need them.
FAQ
Can a Roblox username have a space?
No. The validator only accepts a-z, A-Z, 0-9 and the underscore, and a space is rejected like any other symbol. Display names are the opposite case: a single space between words is accepted there, which is why so many players write their real nickname as a display name and keep a plain username underneath.
How many underscores can a Roblox username have?
Exactly one, and not at the ends. Two underscores return the message that usernames can have at most one, and an underscore at the start or end returns that a username cannot start or end with one. So x_y is fine, x__y is not, and _xy is not.
Does changing your username hide your old one?
No. Roblox states that previous usernames stay visible in your Settings, on your Profile and through People search, and that other players can find them. The original account creation date carries over as well. Treat a name change as adding a name, not erasing one.
How much does a Roblox username change cost?
Roblox does not name a price in the help article; it only says each change requires Robux and that the amount is shown at the Buy step in Account Info. Check the figure in that dialog before confirming, and note that changing back to an old username costs the same again.
Can I use Cyrillic, Japanese or emoji in a Roblox name?
Not in a username: the validator answers that only a-z, A-Z, 0-9 and the underscore are allowed, so Cyrillic and emoji are rejected outright. For display names Roblox says Japanese characters are supported for some users as a beta feature, with more character support planned, but this is not available to everyone.