ULID Generator
Generate universally unique lexicographically sortable identifiers (ULID) online. Decode ULIDs, extract timestamps, and batch create IDs for databases and distributed systems.
What is a ULID?
ULID stands for Universally Unique Lexicographically Sortable Identifier. It is a 126-bit identifier compatible with UUIDs but with improved characteristics for modern distributed systems.
How long is a ULID?
A ULID is 26 characters long when encoded in Crockford Base32, representing 126 bits of data. The format is TTTTTTTTMMMMMMMMMMMMMMMM, where T is timestamp and M is randomness.
What is the difference between ULID and UUID?
ULIDs are lexicographically sortable by creation time, use Crockford Base32 encoding (case-insensitive, no ambiguous characters), and are URL-safe. UUIDs lack time-based sorting and use hex encoding with hyphens.
How does ULID encoding work?
ULID uses Crockford Base32 encoding which uses characters 0-9 and A-Z (excluding I, L, O, U to avoid confusion). This makes ULIDs case-insensitive and URL-safe.
Can I extract the timestamp from a ULID?
Yes, the first 10 characters of a ULID encode a 48-bit Unix timestamp in milliseconds. Our decoder extracts this timestamp and displays it in human-readable format.
Are ULIDs collision-resistant?
Yes, ULIDs have 80 bits of randomness, providing approximately 1.2 x 10^24 possible values per millisecond, making collisions astronomically unlikely.
Can ULIDs be used as database primary keys?
Yes, ULIDs are excellent for database primary keys because they are time-sortable (improving index performance), globally unique, and don't require coordination between nodes.
How many ULIDs can I generate at once?
Our tool supports batch generation of hundreds or thousands of ULIDs at once. Simply specify the quantity and click generate.
Is ULID a standard?
ULID is defined by a public specification at ulid.spec.app. While not an official RFC like UUID (RFC 4122), it is widely adopted in modern software development.
Are ULIDs URL-safe?
Yes, ULIDs use Crockford Base32 encoding which contains only alphanumeric characters, making them safe for URLs, filenames, and other contexts without encoding.
Can ULIDs be sorted chronologically?
Yes, this is one of ULID's key advantages. Since the timestamp is in the most significant position, ULIDs naturally sort in chronological order when compared as strings.
What are ULIDs used for?
ULIDs are used for database keys, distributed tracing, session IDs, resource identifiers in APIs, event sourcing, and anywhere globally unique time-sortable identifiers are needed.
How to Use ULID Generator
Generate ULIDs — universally unique, lexicographically sortable identifiers — and decode existing ones, entirely in your browser. No data is uploaded; everything runs on your device.
- Set how many ULIDs you need and generate a batch in one go — handy for seeding databases or building test fixtures.
- Copy the generated identifiers straight from the output list, one at a time or all together.
- Paste an existing ULID into the decoder to split it into its timestamp and randomness parts.
- Read the extracted timestamp to see exactly when the identifier was created, down to the millisecond.
ULIDs sort chronologically as plain strings, so a database index on them gives you time-ordered rows for free.
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