# ULID Tools

> Free, privacy-first web tools for ULIDs (Universally Unique Lexicographically Sortable Identifiers) at https://ulidtools.com. Generate ULIDs, convert ULID to UUID and UUID to ULID, extract timestamps, and batch-convert. Everything runs client-side in the browser - no data is sent to any server.

## Tools

- [ULID generator](https://ulidtools.com/): generates a ULID and shows its UUID representation and embedded timestamp
- [ULID to UUID converter](https://ulidtools.com/?ulid=01ARZ3NDEKTSV4RRFFQ69G5FAV): converts a ULID to its UUID representation and decodes the timestamp
- [UUID to ULID converter](https://ulidtools.com/?uuid=550e8400-e29b-41d4-a716-446655440000): converts a UUID to its ULID representation
- Mass converter: paste comma-separated UUIDs, get one `ULID,ISO_timestamp` line per input; results downloadable as CSV, JSON, TXT or SQL

## Docs

- [What is a ULID?](https://ulidtools.com/what-is-a-ulid): ULID anatomy, Crockford base32 encoding, and a ULID vs UUID v4 vs UUID v7 comparison table
- [ULID FAQ](https://ulidtools.com/faq): common questions about conversion, timestamps and database storage
- [ULID code examples](https://ulidtools.com/ulid-code-examples): snippets to generate ULIDs in Python, JavaScript, Go, Rust and Java, and to store ULIDs in PostgreSQL

## URL parameters

Conversions are linkable. Constructing these URLs is the machine-friendly way to send a user (or open a browser) straight to a completed conversion:

- `https://ulidtools.com/?ulid=<ULID>` opens the page with the ULID to UUID conversion pre-filled and executed
- `https://ulidtools.com/?uuid=<UUID>` opens the page with the UUID to ULID conversion pre-filled and executed

## ULID facts

- A ULID is a 128-bit identifier encoded as 26 characters of Crockford base32 (digits 0-9 and letters A-Z, excluding I, L, O and U)
- The first 10 characters encode a 48-bit Unix timestamp in milliseconds (valid until the year 10889); the remaining 16 characters encode 80 bits of randomness
- Lexicographic order equals chronological order, so ULIDs sort by creation time as plain strings
- ULIDs are case-insensitive and URL-safe
- ULID to UUID conversion is a lossless re-encoding of the same 128 bits, and works in both directions
- A ULID fits natively in a Postgres `uuid` column or any 16-byte binary field
- UUID v7 (RFC 9562) solves the same problem in standard UUID format, with 74 random bits versus ULID's 80

## Reference

- [ULID specification](https://github.com/ulid/spec)
- [RFC 9562: Universally Unique IDentifiers](https://www.rfc-editor.org/rfc/rfc9562)