ULID Generator

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What Is a ULID and Why Should You Care?

ULIDs, or Universally Unique Lexicographically Sortable Identifiers, are the modern answer to a problem that has plagued developers for years: generating unique IDs that are also sortable by creation time. Our ULID Generator creates these identifiers instantly in your browser, giving you production-ready IDs that you can use in databases, distributed systems, URLs, and anywhere else you need unique, time-ordered identifiers.

If you have ever used UUIDs and been frustrated by their random ordering, inability to extract timestamps, or ugly visual appearance, ULIDs are designed to solve exactly those problems. A ULID looks like 01ARZ3NDEKTSV4RRFFQ69G5FAV: 26 characters, all uppercase alphanumeric, encoding both a millisecond-precision timestamp and 80 bits of randomness. They sort correctly in string order because the timestamp component comes first, encoded in a way that preserves chronological ordering.

ULID vs UUID: The Key Differences

UUIDs (specifically v4) are 128 bits of pure randomness formatted as 32 hex characters with dashes. They are unique, but they tell you nothing about when they were created, and sorting them produces a random order. ULIDs are also 128 bits, but the first 48 bits encode a Unix timestamp in milliseconds, and the remaining 80 bits are random. This design means ULIDs created one after another will sort in creation order, which is enormously useful for database indexing and time-based queries.

ULIDs also avoid the visual noise of dashes and lowercase hex characters. A ULID is a clean, compact, case-insensitive string that works well in URLs, filenames, and user-facing contexts. Many developers who switch from UUIDs to ULIDs find that the improved readability alone justifies the change.

How Our ULID Generator Works

The ULID Generator creates identifiers following the official ULID specification. Each generated ULID contains a 48-bit timestamp component representing the current time in milliseconds since Unix epoch, encoded in Crockford's Base32. The remaining 80 bits are cryptographically random, generated using your browser's secure random number generator. The result is a 26-character string that is globally unique, time-sortable, and URL-safe.

You can generate single ULIDs or batches of multiple ULIDs at once. The tool also typically displays the decoded timestamp so you can verify the embedded time component. Everything runs in your browser with no server involvement.

Where to Use ULIDs

Database primary keys are the most common use case. Using ULIDs as primary keys gives you the uniqueness of UUIDs with the indexing performance of sequential IDs. Because ULIDs are roughly time-ordered, B-tree indexes remain efficient and page splits are minimised. This matters enormously at scale: databases with millions of rows see measurable performance improvements from ULID primary keys compared to random UUIDs.

Distributed systems benefit particularly from ULIDs because they can be generated independently on multiple nodes without coordination, yet they still maintain global time ordering. This eliminates the need for a centralised ID generation service, which would be a single point of failure and a performance bottleneck.

Event sourcing architectures use ULIDs as event IDs because the time-ordering property means events naturally sort in causal order without needing a separate sequence number. Message queues, audit logs, and analytics pipelines all benefit from IDs that carry implicit temporal information.

Crockford's Base32 Encoding

ULIDs use Crockford's Base32, a character encoding that excludes visually ambiguous characters like I, L, O, and U. This reduces transcription errors when humans need to read or type ULIDs. The encoding uses digits 0-9 and letters A-H, J-K, M-N, P-T, V-Z, producing strings that are easy to read, easy to pronounce, and resistant to mistakes.

Generate ULIDs with Confidence

Our browser-based ULID Generator uses cryptographically secure randomness and accurate timestamps to produce specification-compliant ULIDs. No data leaves your browser, no account is required, and there are no usage limits. Whether you need one ULID for a quick test or a hundred for seeding a development database, the tool delivers instantly.