UUID Generator — Free Online v4 and v7 UUIDs
Generate cryptographically random UUIDs in bulk, in any format you need.
🔒 Runs in your browser — files never uploaded ⚡ No signup 💯 Free
crypto.randomUUID(), backed by
the same cryptographic random source as encryption keys — not Math.random().
Nothing is sent to a server, so these are safe to use as real identifiers.
Generate up to 1,000 UUIDs at a time. Version 4 uses your browser's cryptographic random source — the same one that backs encryption keys — so these are safe to use as real identifiers in production.
How to use UUID Generator
- Pick a version — v4 for general use, v7 when the IDs become database keys.
- Set how many you need.
- Choose a format — lowercase, uppercase, braced or dashless.
- Copy or download the list.
v4 vs v7 — and why it matters for your database
v4 is 122 random bits. It is the right default almost everywhere, and collisions are not a practical concern: you would need to generate about 2.7 quintillion of them for a 50% chance of a single duplicate.
v7 puts a millisecond timestamp in the high bits, so UUIDs sort chronologically. This solves a genuine performance problem — inserting random v4 UUIDs into a B-tree primary key scatters writes across the whole index, fragmenting it and hurting insert throughput. v7 appends to the end of the index the way an auto-increment integer does, while staying globally unique and safe to generate on many machines at once. If your UUIDs are going in a primary key column, use v7.
Formats
The canonical form is 36 characters: 32 hex digits in 8-4-4-4-12 groups. The braced form is common in Microsoft ecosystems, and the dashless 32-character form is used where storage is tight — a UUID also fits in 16 raw bytes as a BINARY(16) column.
Frequently asked questions
Are these UUIDs safe to use in production?
Yes. v4 UUIDs come from crypto.randomUUID(), which uses the same cryptographic random source as encryption keys — not Math.random(). They are generated on your device and never transmitted.
Should I use v4 or v7?
Use v7 if the UUIDs will be a database primary key — they sort by creation time, so inserts append to the index instead of fragmenting it. Use v4 everywhere else.
Can two UUIDs ever collide?
In theory, but not in practice. A v4 UUID has 122 random bits; you would need roughly 2.7 quintillion of them for a 50% chance of one duplicate.