ULID Generator
CryptoGenerate sortable Universally Unique Lexicographic IDs (128-bit, timestamp-based). Time-ordered IDs that sort naturally in databases, logs and indexes.
Related Tools
About ULID Generator
A ULID is a 26-character identifier that is globally unique like a UUID but adds a key advantage: its first 48 bits are a millisecond timestamp, so generated IDs are naturally time-ordered and sortable. This tool generates spec-compliant ULIDs locally using the browser's cryptographically secure random source, encoded in case-insensitive Crockford Base32 that drops ambiguous characters, and can emit them in bulk. Every ID is computed locally with no network call, ideal for database primary keys, log entries, or events that need to be both unique and time-sortable.
How to Use
- Open the ULID Generator tool
- Enter the content and set the parameters
- Adjust the output options as needed
- Click the Generate button; results appear in real time
- Copy or export the result
Use Cases
- Sortable primary keys — Use ULIDs as DB primary keys so insert order matches time, aiding range queries and index locality.
- Log/event IDs — Assign time-sortable unique IDs to logs or event streams to trace ordering.
- Distributed generation — Multiple nodes generate collision-free, roughly ordered IDs without coordination.
- Replace auto-increment — Get ordered IDs without revealing record counts, safer than sequential keys.
- Bulk pre-generation — Produce many ULIDs at once for bulk imports or pre-allocated identifiers.
- Event sourcing IDs — Generate ULIDs for event store entries so replay order matches the original event timeline.
- Migration key mapping — Pre-generate ULIDs for new rows before a data migration to keep foreign key references intact.
FAQ
How do I choose between ULID and UUID?
Pick UUID for pure randomness and broad standard compatibility; pick ULID for time ordering and friendlier DB indexes. The ULID time prefix keeps new rows at the end, avoiding the index fragmentation random UUIDs cause. Use our UUID generator if you need a UUID.
Is a ULID strictly monotonic?
It increases with time at millisecond granularity, but the order of multiple ULIDs within the same millisecond is set by the random part. The spec offers a monotonic mode that increments the random bits within a millisecond for strict ordering.
Why Crockford Base32?
This encoding drops characters like I, L, O, and U that confuse with digits or spell unwanted words, is case-insensitive, and is friendlier for hand-copying and use in URLs.
Does a ULID expose its creation time?
Yes. The first 10 characters decode to a millisecond timestamp, which is a plus when you need ordering, but if you do not want to reveal creation time, switch to a purely random identifier.
Can 26 characters collide?
The timestamp takes 48 bits and the random part 80 bits. A collision within the same millisecond would require generating an astronomical number of IDs, so in practice they are unique.
Is ULID faster to generate than UUID?
They are essentially the same order of magnitude. The timestamp comes from the system clock and the random part from a single cryptographically secure call — purely local, with no network or coordination, so it easily serves high-throughput flows producing an ID per request. If you ever need a huge burst of ULIDs within a single millisecond, the spec's monotonic mode increments the random bits for strict ordering. In practice no caching or pre-generation is required to hit performance targets.
Does ULID really reduce database index fragmentation?
Yes — that is its main advantage over random UUIDs. The 48-bit millisecond prefix puts new IDs mostly at the tail of the index, making writes near-append-only with higher page-hit ratios, fewer splits, and friendlier range reads. Ordering, however, is only at millisecond granularity; multiple IDs within the same millisecond remain random-ordered. For strict global ordering across nodes, look at a snowflake-style scheme; when all you need is sortable and unique, ULID is usually the lighter, well-specified choice.