UUID Generator: Create UUID v4, ULID, and NanoID Online
Need a unique identifier? Whether you're setting up database records, generating API keys, or building test data, a UUID generator is one of those tools developers reach for constantly. This one generates UUID v4, ULID, and NanoID formats — take your pick.
UUID v4: The Classic Choice
UUID v4 is the most common format. It's a 128-bit random identifier that looks like this: 550e8400-e29b-41d4-a716-446655440000. The odds of generating a duplicate are astronomically small — we're talking about 2^122 possible combinations. You could generate a billion UUIDs per second for 85 years and still have less than a 50% chance of a collision.
I use UUID v4 for most things — database primary keys, session tokens, file identifiers, tracking IDs. It's the default choice when you just need something unique and don't have special requirements.
ULID: When Sorting Matters
ULIDs (Universally Unique Lexicographically Sortable Identifiers) solve a real annoyance with UUIDs — they're sortable by creation time. A ULID looks like 01ARZ3NDEKTSV4RRFFQ69G5FAV and encodes a timestamp in the first 48 bits.
This matters when you're using IDs as database primary keys and want them to be roughly ordered by creation time. With regular UUIDs, new records get scattered randomly across your index. With ULIDs, they're naturally sequential, which is better for database performance.
NanoID: Short and Sweet
NanoID generates shorter identifiers — typically 21 characters by default, compared to UUID's 36. They look like V1StGXR8_Z5jdHi6B-myT. Same level of uniqueness guarantees, smaller footprint.
I reach for NanoID when the identifier shows up in URLs or user-facing contexts where a full UUID feels too long. It's URL-safe by default and uses a larger alphabet, so you get the same entropy in fewer characters.
Bulk Generation
Need more than one? The UUID generator lets you create up to 1000 identifiers at once. Just set your quantity, pick your format, and click generate. The results are ready to copy — one per line, perfect for pasting into a script or SQL insert statement.
I honestly use the bulk feature all the time when I'm setting up test data. Way faster than writing a script to generate them.
Which Format Should You Use?
Here's my quick take: UUID v4 for most database and backend use cases. ULID when you need time-sortable IDs (especially as primary keys). NanoID when you need shorter IDs for URLs or user-facing contexts. All three give you effectively zero collision risk.