UUID / ULID Generator

How to use the UUID / ULID Generator

1. Select the identifier type: UUID v4 or ULID.
2. Set the count (1-100) and click Generate.
3. Click Copy All to copy every generated ID to your clipboard at once.

UUID v4

UUID (Universally Unique Identifier) v4 is a 128-bit identifier generated from cryptographically secure random numbers. It is formatted as five hyphen-separated groups of hexadecimal digits: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. The 4 in the third group indicates the version, and the first one or two bits of the fourth group indicate the variant.

The probability of generating two identical UUID v4s is astronomically small, you would need to generate about 2.7 quintillion UUIDs before having a 50% chance of a collision. They are safe to use as primary keys, session tokens, and correlation IDs without coordination between systems.

ULID

ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit identifier that encodes a millisecond-precision Unix timestamp in the first 10 characters, followed by 16 random characters. Format: 01ARZ3NDEKTSV4RRFFQ69G5FAV (26 characters, Crockford Base32).

The key advantage over UUID: ULIDs sort lexicographically in creation order. This makes them much more efficient as database primary keys, B-tree indexes stay ordered, and range queries by creation time work naturally without a separate timestamp column.

UUID vs ULID: which to choose?

Common use cases

• Database primary keys: UUID or ULID as the ID for any record, avoiding auto-increment integers that leak record counts
• Session tokens: generate a UUID to identify a user session stored server-side
• File names: rename uploaded files with a UUID to prevent conflicts and enumeration
• Distributed systems: generate IDs on any node without coordination or a central sequence generator

Privacy

Generation uses the browser's crypto.randomUUID() API and crypto.getRandomValues(). Nothing is sent to any server.