UUID & ULID generator
UUID v4, UUID v7 (time-based, RFC 9562) and ULIDs — bulk generation and validator.
UUID v4 is random. UUID v7 and ULID start with the time and can therefore be sorted in order.
How many identifiers are generated at once, 1 to 10,000.
Paste a UUID with hyphens (36 characters) or a ULID (26 characters) to check its format and version.
How this tool works
Generates UUIDs (Universally Unique Identifiers) in the common versions 4 (random, RFC 4122) and 7 (time-based, new since 2024), as well as ULIDs (Universally Unique Lexicographically Sortable Identifier — compact, sortable, 128 bit). Bulk-generate 1, 10, 100 or 1000 IDs on click. The tool also includes a validator that identifies which version a pasted UUID belongs to, plus converters between UUID, hex and base64 forms. All operations run in-browser via crypto.randomUUID().
Typical use cases
- Generate test data for databases or API mocks
- Assign IDs in frontend lists before server response (optimistic UI)
- Generate tracking IDs for logs and distributed tracing
- Bulk IDs for migration scripts or seed data
- Validate: is this UUID v4 or v7? Does it have correct variant bits?
Frequently asked questions
What is the difference between UUID v4 and v7?
v4 is 100% random — best for privacy, bad for database index performance. v7 contains a timestamp in the first 48 bits — sortable, dramatically faster B-tree inserts. Standardised in RFC 9562 (2024).
What is a ULID?
A 128-bit ID like UUID but encoded as 26-character Crockford base32 — shorter, URL-safe, lexicographically sortable. Often a better choice than UUID v7 because more compact.
Are UUIDs cryptographically secure?
Yes — we use crypto.randomUUID() which is backed by the browser CSPRNG. Still: 122 random bits (UUID v4) are enough for session tokens — for highly sensitive tokens prefer raw 256-bit random.
How many UUIDs can I generate at once?
Up to 10,000 are performant in-browser. Beyond that, prefer batch generation in Node.js or a database function.
Are generated UUIDs stored?
No. IDs are generated purely in your browser — no server, no log, no cache.
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