ULID Generator
Generate and decode time-sortable unique identifiers (ULIDs), a modern, index-friendly alternative to UUIDs.
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ℹ️ A ULID is a 26-character identifier consisting of a 10-character (48-bit) millisecond timestamp followed by a 16-character (80-bit) random number. Its lexicographical sort order matches its generation order, which is advantageous for database indexing. It uses Crockford Base32, which excludes easily confused characters (I, L, O, U), making it human-friendly for transcription. When Monotonic is enabled, if multiple ULIDs are generated within the same millisecond, the random part is incremented to maintain order (otherwise, order within the same millisecond may be mixed).
🔒 Values are generated using the browser's cryptographic random number generator (crypto.getRandomValues) and are not sent to the server. Since the generation time is embedded directly in the value, do not use it in contexts where the time must be hidden.
What is the ULID Generator?
Need unique, sortable IDs that improve database performance? This tool generates ULIDs (Universally Unique Lexicographically Sortable Identifiers), a powerful alternative to UUIDs. A ULID is a 26-character string where the first part is a timestamp, meaning they can be sorted by creation time just by sorting the text. This is a major advantage for database indexing. Our free online generator lets you create multiple ULIDs at once, with an option to guarantee monotonic order even within the same millisecond. It also includes a decoder: just paste any ULID to see its exact creation time and components. All generation and decoding happens securely in your browser; no data is sent to our servers.
How to use
- Set the `Count` and select options like `Monotonic` for strict sorting or `Lowercase` for formatting.
- Click the `Generate` button. Your list of ULIDs appears instantly in the `Result` box below.
- Use `Copy All` to copy the list to your clipboard, or click `Save` to download it as a 'ulid.txt' file.
- To analyze an existing ID, paste a 26-character ULID into the `Decode ULID → Timestamp` input field.
- The ULID's components—timestamp, random part, and creation time—are displayed in a table as you type.
- Click `Use First Result` to quickly send the first ULID from your generated list to the decoder for analysis.
Frequently asked questions
How is a ULID different from a UUID?
The main difference is sortability. A ULID's prefix is a timestamp, so sorting the ID string also sorts it by time. A standard v4 UUID is random and cannot be sorted chronologically. This makes ULIDs better for database indexing. ULIDs also use a more human-readable character set.
What does the 'Monotonic' option do?
When you generate ULIDs very quickly, multiple can be created in the same millisecond. This option guarantees they remain in strict creation order by incrementing the random part for each one. With this option off, their order within the same millisecond might be mixed.
Are ULIDs truly unique? What about collisions?
Yes, they are unique for all practical purposes. A ULID combines a 48-bit timestamp with an 80-bit cryptographically secure random number. The chance of two identical ULIDs being generated in the same millisecond is astronomically low, so collisions are not a concern in typical use.
Are the values I generate secure?
Yes. This tool runs entirely in your browser. It uses the browser's built-in cryptographic random number generator, and no values you generate or decode are ever sent to a server. However, remember that the creation time is embedded in the ULID itself, so don't use it where that information is sensitive.