Generate, decode, and validate ULIDs instantly
Free ULID generator to create universally unique, lexicographically sortable identifiers. Generate single or bulk ULIDs, decode timestamps, and validate format. 100% client-side, your data never leaves your browser.
01ARZ3NDEKTSV4RRFFQ69G5FAV
| Length | 26 characters |
| Encoding | Crockford Base32 |
| Size | 128 bits (16 bytes) |
| Sortable | Yes, lexicographically |
| Case | Case-insensitive |
| Length | ULID: 26, UUID: 36 |
| Sortable | ULID: Always, UUID v4: No |
| Encoding | ULID: Base32, UUID: Hex |
| Timestamp | ULID: Always, UUID v4: No |
| URL-safe | ULID: Yes, UUID: Needs encoding |
ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit identifier that combines a timestamp with randomness. It is encoded as a 26-character string using Crockford Base32. Unlike UUID v4 which is random and unsortable, ULIDs are always sorted by creation time when you sort them as strings.
ULIDs were created as a modern alternative to UUIDs for cases where time-ordering matters, like database primary keys, event logs, and distributed systems.
A ULID has two parts:
The encoding uses Crockford Base32, which excludes the letters I, L, O, and U to avoid visual confusion with digits. This makes ULIDs easy to read, copy, and type.
When multiple ULIDs are generated in the same millisecond, the random portion can either be fully random (which doesn't guarantee sort order within that ms) or monotonically incremented.
Monotonic generation takes the previous ULID's random bits and adds 1. This guarantees strict ordering even when generating thousands of IDs per millisecond. Most ULID libraries support this mode.
Generate UUIDs with our UUID Generator or decode distributed IDs with the Snowflake ID Decoder.
ULIDs use Crockford Base32 which encodes 5 bits per character using this alphabet:
0123456789ABCDEFGHJKMNPQRSTVWXYZ
This results in 26 characters for 128 bits, compared to 36 characters for a UUID. ULIDs are case-insensitive: 01ARZ3NDEK and 01arz3ndek are the same ULID.
A ULID is a 128-bit unique identifier encoded as 26 Crockford Base32 characters. It combines a 48-bit millisecond timestamp with 80 bits of randomness. ULIDs are sortable by creation time, case-insensitive, and URL-safe.
ULIDs are 26 characters (Base32), always sortable, and always contain a timestamp. UUIDs are 36 characters (hex), and only v1 and v7 contain timestamps. UUID v4, the most common version, is random and not sortable. ULIDs are shorter and better for database primary keys.
Yes. The timestamp is encoded first, so standard string sorting puts ULIDs in chronological order. This is the main advantage over UUID v4.
Yes, and they work great. Because ULIDs are time-sorted, new rows always append to the end of B-tree indexes. This avoids the page splits and fragmentation that random UUIDs cause.
An encoding that uses 32 characters: digits 0-9 and letters A-Z excluding I, L, O, U. It avoids characters that look similar (I vs 1, O vs 0). It is case-insensitive and produces shorter strings than hexadecimal.
When multiple ULIDs are generated in the same millisecond, monotonic mode increments the random portion instead of generating new random bits. This guarantees strict sort order within the same millisecond.
With 80 bits of randomness per millisecond, collisions are practically impossible. You would need to generate about 1.21 x 1012 ULIDs in the same millisecond for a 50% collision chance. With monotonic generation, collisions are impossible by design.
Yes. This tool uses crypto.getRandomValues() for cryptographically secure randomness. All ULIDs are generated entirely in your browser. No data is sent to any server.