Developer / Browser tools
ULID Generator
Generate sortable ULIDs, keep same-millisecond values monotonic, and decode a ULID timestamp.
ULID Generator: Generate sortable ULIDs, keep same-millisecond values monotonic, and decode a ULID timestamp. Runs 100% locally in your browser with zero server file uploads.
- Category
- Developer tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
A ULID contains a 48-bit timestamp and 80 bits of randomness. Monotonic mode increments the random part within the same millisecond and holds the previous timestamp if the clock moves backwards. ULIDs reveal creation time and are not passwords. ULID specification · UUID generator
ULID specification
Canonical ULID specification, encoding, timestamp and monotonic rules: https://github.com/ulid/spec . The largest accepted value is 7ZZZZZZZZZZZZZZZZZZZZZZZZZ; values above the 48-bit timestamp limit are rejected.
Generation and decoding
Generation starts with browser cryptographic randomness. If the 80-bit random suffix overflows within the same timestamp, generation fails instead of wrapping.
Decoding accepts uppercase or lowercase valid characters and displays UTC. It extracts an encoded time, not a verified creation record.
How to use it
- Choose a count and whether to keep generation monotonic.
- Generate and copy identifiers.
- Paste a ULID to read its UTC timestamp and Unix milliseconds.
Privacy & limitations
Your inputs stay in this browser. Nothing you enter is uploaded or saved.
Related tools
Frequently asked questions
What is inside a ULID?
A 48-bit millisecond timestamp and 80-bit random part encoded as 26 Crockford Base32 characters. I, L, O and U are excluded.
What does monotonic mode guarantee?
Within this page session, the random part increments when the timestamp is unchanged. If the clock moves backwards, the previous timestamp is retained. Separate tabs or devices do not share this ordering state.
Can I use a ULID as a password?
No. It exposes creation time, and monotonic values have a predictable increment. Use the password generator for passwords.
Free tool · runs in your browser · no account required