UUID & ID Generator
Generate unique identifiers instantly.
Generated IDs 0
UUID v4
Universally Unique Identifier version 4. 128-bit random value formatted as 32 hex digits in 8-4-4-4-12 groups. Standard for most applications.
ULID
Universally Unique Lexicographically Sortable Identifier. Time-ordered so IDs sort chronologically. Great for database primary keys.
Nano ID
Compact, URL-safe unique string identifier. 21 characters using A-Za-z0-9_-. Smaller and faster than UUID.
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit value used to uniquely identify
information across distributed systems without requiring a central authority. Defined by RFC 4122, UUIDs are formatted as 32 hexadecimal digits displayed in five groups separated by
hyphens (8-4-4-4-12), such as 550e8400-e29b-41d4-a716-446655440000. Version 4 UUIDs,
which this tool generates by default, are created using cryptographically secure random
numbers, providing 122 bits of randomness and an astronomically low collision probability.
While UUIDs are the most widely adopted standard, alternatives like ULID and Nano ID have emerged to address specific use cases. ULIDs embed a timestamp prefix that makes them lexicographically sortable, which is ideal for database indexing. Nano IDs offer a more compact 21-character format using a URL-safe alphabet, making them suitable for client-side identifiers and short URLs. All three formats rely on cryptographic randomness for uniqueness.
UUID vs ULID vs Nano ID
| Feature | UUID v4 | ULID | Nano ID |
|---|---|---|---|
| Format | Random | Time-sortable | Compact, URL-safe |
| Length | 36 characters | 26 characters | 21 characters |
| Encoding | Hexadecimal | Crockford Base32 | A-Za-z0-9_- |
| Standard | RFC 4122 | ULID spec | Community |
| Best for | Maximum compatibility, cross-system identifiers | Database primary keys, time-ordered records | Short URLs, client-side IDs, compact tokens |
FAQ
Can UUIDs collide?
Theoretically yes, but the probability is astronomically low. UUID v4 has 122 bits of randomness, giving a collision probability of roughly 1 in 2122. You would need to generate about 2.7 quintillion UUIDs to have a 50% chance of a single collision. For all practical purposes, they are unique.
Should I use UUID or ULID for database primary keys?
Use ULID if you need time-ordering and better index performance. Because ULIDs are lexicographically sortable by creation time, they produce sequential inserts that are friendlier to B-tree indexes. Use UUID v4 when maximum compatibility is the priority, since virtually every database, language, and framework supports them natively.
Are generated IDs cryptographically secure?
Yes. All three formats produced by this tool use crypto.getRandomValues() for randomness, which is a cryptographically secure pseudorandom number generator (CSPRNG)
provided by your browser. The IDs are safe for use as tokens, session identifiers, and other
security-sensitive contexts.
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