ULID Generator
Generate compact, sortable, URL-safe unique identifiers
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Click "Generate" to create UUIDs
UUID v4
Random UUIDs. Most commonly used for general purposes.
UUID v7
Time-ordered and random. Best for databases and sorting.
ULID
Sortable 26-char IDs. Perfect for distributed systems.
NanoID
Compact 21-char URL-safe IDs. Great for frontend use.
01ARZ3NDEKTSV4RRFFQ69G5FAVWhat is ULID?
ULID (Universally Unique Lexicographically Sortable Identifier) addresses UUID's main weaknesses: poor sortability and inefficient string representation. At 26 characters using Crockford's Base32, ULIDs are shorter than UUIDs while maintaining 128-bit uniqueness.
The first 10 characters encode a 48-bit Unix timestamp in milliseconds, while the remaining 16 characters encode 80 bits of randomness. This gives you time-ordering by default with collision resistance comparable to UUID v4.
Why Use ULID?
ULIDs are more practical than UUIDs in many scenarios. They're URL-safe without encoding, case-insensitive, and sort correctly as strings. Database indexes on ULID columns perform better because of natural time-ordering.
The compact representation (26 vs 36 characters) saves storage and bandwidth. In URLs, API responses, and logs, this 28% reduction adds up across millions of identifiers.
How ULID Works
ULID generation:
1. Get Unix timestamp in milliseconds (48 bits) 2. Generate 80 bits of randomness 3. Encode timestamp as 10 Crockford Base32 characters 4. Encode randomness as 16 Crockford Base32 characters 5. Concatenate: TTTTTTTTTTРRRRRRRRRRRRRRRR
Crockford's Base32 excludes I, L, O, U to avoid confusion and profanity.
Common Use Cases
- URL-friendly resource identifiers
- Log correlation across services
- Database primary keys needing sortability
- APIs prioritizing compact responses
Pro Tip
ULID's monotonic option ensures IDs generated in the same millisecond are still ordered correctly.
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