What is a ULID?
ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit identifier that is compatible with UUIDs but offers a significant advantage: lexicographical sortability.
Unlike random UUIDs (v4), which scatter data across database indexes and cause fragmentation, ULIDs are time-ordered. This means they naturally sort by creation time, making them highly efficient for database primary keys, especially in high-volume systems.
- 128-bit compatibility with UUID.
- 1.21e+24 unique ULIDs per millisecond.
- Lexicographically sortable!
- Crockford's Base32 encoded (case-insensitive, safe for URLs).
- Monotonic sort order (correctly detects and handles the same millisecond).
Why Use Our Advanced ULID Generator?
Whether you are designing a distributed system or just need a quick unique ID, our tool provides:
- Instant Generation: Generate thousands of ULIDs in milliseconds directly in your browser.
- Raw & JSON Formats: Copy a list of IDs or get a ready-to-use JSON array for your API or config files.
- Time Decoding: See exactly when each ULID was generated with our detailed breakdown.
- Secure & Private: All generation happens locally on your device (Client-Side) or securely via our optimized backend.
ULID vs. UUID: Which Should You Choose?
While UUID v4 is the industry standard for randomness, it has a major flaw: it's not sortable. This leads to index fragmentation in databases like MySQL, PostgreSQL, and SQL Server.
| Feature | UUID (v4) | ULID |
|---|---|---|
| Sortable? | No | Yes |
| Randomness | 122 bits | 80 bits |
| Timestamp | None | 48 bits (ms precision) |
| Encoded As | Hexadecimal (36 chars) | Crockford Base32 (26 chars) |
Structure of a ULID
Stores the UNIX timestamp in milliseconds. Readable and sortable.
Cryptographically secure random data to ensure uniqueness.
Frequently Asked Questions
Is ULID collision-free?
For all practical purposes, yes. With 80 bits of randomness, the collision probability is extremely low, similar to UUIDs.
Can I use ULID in a URL?
Yes! ULIDs use Crockford's Base32 encoding, which is URL-safe, case-insensitive, and excludes confusing characters like I, L, O, and U.
Does this tool work offline?
Yes, our client-side generator works entirely in your browser after the page loads.