UUID generator
Generate up to 1,000 UUIDs at once: random version 4 or time-ordered version 7. Choose upper case, no dashes or {braces}, then copy them all or download a text file.
Common mistakes
Using v4 as a database primary key at scale
Random keys land all over a B-tree index, which slows inserts on big tables. v7 keys arrive in time order and avoid that.
Treating a v7 UUID as private
Its first 12 hex digits are the creation time in milliseconds. Anyone can read when the ID was made; the checker below shows it.
Comparing UUIDs as case-sensitive strings
UUIDs are case-insensitive: 550E8400… and 550e8400… are the same ID. Normalise to lower case before comparing or storing.
Storing UUIDs as 36-character text
Most databases have a native UUID type that stores the 16 bytes. Text takes more than twice the space and compares more slowly.
How it works
- 1
Pick a version and how many
v4 is fully random. v7 starts with the current time in milliseconds, so new IDs sort after older ones.
- 2
Choose the format
Lower or upper case, with or without dashes, and with braces for the Windows GUID style. Changing the format doesn’t change the IDs.
- 3
Copy or download
Copy all of them, download a .txt with one per line, or press Regenerate for a fresh batch. Paste any UUID in the checker to see its version.
Questions
- What is the difference between UUID v4 and v7?
- Version 4 is 122 random bits. Version 7 (RFC 9562) puts a 48-bit Unix timestamp in milliseconds first, then random bits, so IDs created later sort later. That keeps database indexes compact when UUIDs are primary keys.
- Is a UUID the same as a GUID?
- Yes. GUID is Microsoft’s name for the same 128-bit format. Windows tools often show it in upper case inside braces, like {3F2504E0-4F89-41D3-9A0C-0305E82C3301}; the Braces and Uppercase switches give you that form.
- Can two generated UUIDs collide?
- In practice, no. With 122 random bits you would need to generate around 2.7 quintillion v4 UUIDs for a 50% chance of a single duplicate. Within one v7 batch, a counter keeps every ID in the same millisecond distinct and in order.
- Are these UUIDs random enough for secrets?
- They come from crypto.getRandomValues, the browser’s secure random source. Still, a UUID is an identifier, not a password: v7 also reveals when it was made.
- Are the UUIDs saved or sent anywhere?
- No. They are generated in this tab and aren’t stored; only your options are remembered in this browser.