Roblox User Lookup (User ID and Username)

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roblox username checker

Roblox Username Checker with the reason for the rejection

In the Username checker tab, write the name you want. Format rules are evaluated instantly, with no network, and names with a valid format go through the same check Roblox runs at sign-up.

The rules, in the order Roblox applies them

A valid name has 3 to 20 characters, only letters A to Z without accents, digits 0 to 9 and at most one underscore, which cannot sit at the start or the end, and no space. When several problems stack up, the returned code follows an order we measured on the API: length first (code 3), then a disallowed character (7), underscore at the ends (4), more than one underscore (5) and, last, a space (6). That is why "a b-c" gets 7, not 6, and "a b_" gets 4.
What is left depends on Roblox: 0 is available, 1 is a name already in use, 2 is a rejection by the moderation filter, 10 describes a name with personal information and 12 a reserved name. Codes 10 and 12 come from the official documentation and we did not trigger them in tests, so their text follows the documentation. A code outside the table is shown as an unrecognized answer and never as available.
Available is not reserved. The result holds for the moment of the check and stays cached for up to 1 minute; anyone can register the name before you, and the real sign-up may apply filters beyond this check. The route requires a birth date, and the tool sends a fixed adult date, so the result for an underage account may differ.

Names and the code each one gets

Too short

Input: ab
Expected output: 3

The minimum is 3 characters.

Hyphen

Input: ab-c
Expected output: 7

Only letters, numbers and underscore.

Leading underscore

Input: _abc
Expected output: 4

It also applies to the end: abc_.

Two underscores

Input: a_b_c
Expected output: 5

At most one in the middle of the name.

With a space

Input: a b
Expected output: 6

Swap the space for an underscore.

A name that exists

Input: builderman
Expected output: 1

Answer from Roblox: in use.

Full tool FAQ

How do I find someone's User ID on Roblox?

Type the username in the Lookup tab. The ID shows up large, with a copy button. On the website the same number is in the profile address: roblox.com/users/156/profile is the account with ID 156 (builderman). You can also paste that whole link here and the tool extracts the ID.

Does the User ID change when someone changes their username?

What is the difference between a username and a display name?

How do I know if a username is available?

Why does a name show as in use when the account is gone in the app?

How do I see an account's past usernames?

How many usernames or IDs can I convert at once?

How do I convert a username to an ID inside a Luau script?

Why are friends, followers or following sometimes blank?

Does the tool store data or access private information?

Frequently asked questions

Does checking a name put my account at risk?

Not here. The check leaves from our server, without your account, login or cookie, and it is a read-only query. Extensions that automate checks inside your session are another story and can trigger blocks.

Why do digits-only names often show as in use?

Digits-only names are valid in format and many were already registered: 12345678, for example, belongs to the account with ID 22025. The checker returns code 1 and the Lookup tab shows whose it is.

Can I check several names at once?

The checker tests one name at a time, with a 0.7 s delay after the last keystroke. To find out which names in a list already have an owner, paste them in the Batch tab: it returns the ID of those that exist and marks the others as not found.

Next steps

The rules, in the order Roblox applies them

Code	Meaning
0	Available to register Roblox accepted this name in the sign-up check.
1	Already in use An account with this name exists. Usernames are unique and not case sensitive.
2	Rejected by moderation Roblox's content filter blocked this name as inappropriate for the platform.
3	Invalid length The name must be 3 to 20 characters long.
4	Underscore at the start or end The name cannot start or end with _.
5	Too many underscores The name can have at most one _.
6	Contains spaces Spaces are not allowed. Use an underscore instead.
7	Characters not allowed Only letters A to Z (no accents), digits 0 to 9 and one underscore are valid.
10	Looks like personal information Roblox's documentation describes this code as a name that contains personal data, such as a phone number or email.
12	Reserved name Roblox's documentation describes this code as a name reserved by the platform.

A valid name has 3 to 20 characters, only letters A to Z without accents, digits 0 to 9 and at most one underscore, which cannot sit at the start or the end, and no space. When several problems stack up, the returned code follows an order we measured on the API: length first (code 3), then a disallowed character (7), underscore at the ends (4), more than one underscore (5) and, last, a space (6). That is why "a b-c" gets 7, not 6, and "a b_" gets 4.

What is left depends on Roblox: 0 is available, 1 is a name already in use, 2 is a rejection by the moderation filter, 10 describes a name with personal information and 12 a reserved name. Codes 10 and 12 come from the official documentation and we did not trigger them in tests, so their text follows the documentation. A code outside the table is shown as an unrecognized answer and never as available.

Available is not reserved. The result holds for the moment of the check and stays cached for up to 1 minute; anyone can register the name before you, and the real sign-up may apply filters beyond this check. The route requires a birth date, and the tool sends a fixed adult date, so the result for an underage account may differ.

Names and the code each one gets

Too short

Input: ab
Expected output: 3

The minimum is 3 characters.

Hyphen

Input: ab-c
Expected output: 7

Only letters, numbers and underscore.

Leading underscore

Input: _abc
Expected output: 4

It also applies to the end: abc_.

Two underscores

Input: a_b_c
Expected output: 5

At most one in the middle of the name.

With a space

Input: a b
Expected output: 6

Swap the space for an underscore.

A name that exists

Input: builderman
Expected output: 1

Answer from Roblox: in use.

Full tool FAQ

How do I find someone's User ID on Roblox?

Does the User ID change when someone changes their username?

What is the difference between a username and a display name?

How do I know if a username is available?

Why does a name show as in use when the account is gone in the app?

How do I see an account's past usernames?

How many usernames or IDs can I convert at once?

How do I convert a username to an ID inside a Luau script?

Why are friends, followers or following sometimes blank?

Does the tool store data or access private information?

Frequently asked questions

Does checking a name put my account at risk?

Why do digits-only names often show as in use?

Digits-only names are valid in format and many were already registered: 12345678, for example, belongs to the account with ID 22025. The checker returns code 1 and the Lookup tab shows whose it is.