BracketUUID / ULID Generator
Generate v4 UUIDs or ULIDs in bulk, one click to copy. Uses your browser's cryptographically secure random number generator.
🔒 Runs entirely in your browser — no data is ever sent anywhereWhen you need a UUID or ULID
Any time you need a unique identifier that doesn't depend on a central database counter — a primary key for a new database row, an idempotency key for a payment API call, a request ID to trace through distributed logs, or just realistic-looking mock data for a test fixture — a UUID or ULID does the job without any coordination between services. ULIDs specifically are a good fit wherever you also want IDs to sort in the order they were created, something a random UUID can't give you.
v4 UUID vs ULID — and how the randomness is generated
A v4 UUID is 128 bits, of which 122 are genuinely random (the remaining 6 are fixed to mark the version and variant per the UUID spec) — with no relationship to when it was created. A ULID instead spends its first 48 bits on a millisecond timestamp and the remaining 80 on randomness, so ULIDs generated later always sort lexicographically after earlier ones, which is genuinely useful for a database index. Both are generated here using crypto.getRandomValues(), the browser's cryptographically secure random number source — not Math.random(), which isn't designed to be unpredictable and shouldn't be used anywhere uniqueness or security matters.
Frequently asked questions
What's the difference between a UUID and a ULID?
A v4 UUID is 128 bits of random data with no inherent ordering. A ULID encodes a timestamp in its first 48 bits, so ULIDs generated later always sort after earlier ones — useful for database primary keys where you want both uniqueness and chronological order.
Are the generated UUIDs cryptographically random?
Yes — this tool uses the browser's crypto.getRandomValues() API, a cryptographically secure random number generator, not Math.random().
Can two generated UUIDs ever collide?
Technically possible but astronomically unlikely: a v4 UUID has 122 random bits, so even generating a billion of them per second, it would take roughly 86 years before you'd have a 50% chance of one collision.
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