UUID Generator — Bulk UUID v4 and v7
Create UUID v4 and sortable v7 values in bulk
Runs in your browser · nothing is uploaded
What it is
A UUID is a 128-bit identifier that can be created independently on any machine with a negligible chance of repeating, which is why it shows up in database keys, file names and request tracing. This tool makes v4 or v7 UUIDs, up to 1000 per click.
How to use
- Choose the version: v4 is fully random, v7 is time-ordered.
- Set how many you want, from 1 to 1000.
- Switch on uppercase or turn off hyphens if you need that style.
- The list updates immediately. Copy puts the whole list on your clipboard, one UUID per line.
- Press Generate again for a fresh batch.
How it works
- Output follows RFC 9562 (which replaced RFC 4122): 32 hex digits grouped 8-4-4-4-12.
- v4 comes from the browser’s
crypto.randomUUID: version nibble 4, variant bits 10, and 122 random bits. - v7 is built by hand: a 48-bit Unix timestamp in milliseconds, version 7, a 12-bit counter, variant bits 10, then 62 random bits.
- Sort order is guaranteed within one generated batch (and across batches in the same browser session). Several ids in the same millisecond increment the 12-bit counter. If the clock stalls or steps backwards the value never drops below the previous one, so sorting the strings gives the creation order. If the counter would overflow within one millisecond, the timestamp moves forward by one.
- All randomness comes from
crypto.getRandomValues;Math.randomis never used.
Examples
| Item | Shape |
|---|---|
| v4 | xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx (y is 8, 9, a or b) |
| v7 | tttttttt-tttt-7xxx-yxxx-xxxxxxxxxxxx (t is the millisecond timestamp, y is 8, 9, a or b) |
| No hyphens | One run of 32 hex digits |
| Uppercase | The same value with A–F capitalised |
Generate a v7 batch and sort the lines alphabetically: the order will not change.
FAQ
Should I pick v4 or v7?
Use v4 when you only need a unique ID. Use v7 for things like database primary keys, where ids that sort by creation time keep indexes friendlier.
Can two UUIDs collide?
In theory yes, but a v4 has 122 random bits, so collisions are not a practical worry at normal scale. v7 adds a counter so ids made in the same millisecond stay unique and ordered.
Is it a problem that v7 contains a timestamp?
The first 48 bits of a v7 are the creation time in milliseconds. Use it only where revealing creation time is fine, and choose v4 when it is not.
Are the UUIDs stored anywhere?
No. They are produced with the browser's cryptographic random source and never sent anywhere.
