Ulid Generator

Free online tool. All processing is client-side. No signup needed.

How to Use the Ulid Generator

1. Enter your input values above
2. Results update automatically
3. Copy or download the output

What is a Ulid Generator?

A ULID (Universally Unique Lexicographically Sortable Identifier) Generator creates identifiers that are both globally unique AND time-sortable — combining the uniqueness of UUIDs with the sortability of timestamps. A ULID consists of a 48-bit timestamp (milliseconds since Unix epoch, giving ~89 years of range from 1970) followed by 80 bits of randomness. This means ULIDs sort chronologically when sorted as strings, making them vastly better for database primary keys than UUID v4 (which sorts randomly, causing B-tree index fragmentation). In 2026, ULIDs are increasingly adopted over UUIDs for new database designs.

How Does It Work?

Choose the number of ULIDs to generate (1-100). Each ULID is a 26-character Crockford Base32 string (using 0-9 and A-Z excluding I, L, O, U to avoid confusion with 1, 1, 0, V). The first 10 characters encode the Unix timestamp in milliseconds; the next 16 characters are random. Example: 01ARZ3NDEKTSV4RRFFQ69G5FAV. Because of the timestamp prefix, ULIDs sort naturally by creation time.

Formula

ULID Format (26 characters, Crockford Base32):\n\nttttttttttrrrrrrrrrrrrrrrr\n│          │                │\n│          │                └─ 80 random bits (16 chars)\n│          └─ 48-bit timestamp in ms (10 chars)\n└─ Total: 128 bits, same as UUID\n\nTimestamp: Number of milliseconds since 1970-01-01T00:00:00.000Z\nRange: Valid until ~5139 AD\n\nCrockford Base32 Alphabet: 0123456789ABCDEFGHJKMNPQRSTVWXYZ\n(excludes I, L, O, U to prevent visual confusion)\n\nCharacters per component:\n• Timestamp (48 bits): 10 chars (48 ÷ 5 ≈ 9.6 → 10)\n• Random (80 bits): 16 chars (80 ÷ 5 = 16)\n\nString sort order = chronological order (by design)\n\nUUID v4 comparison: 32 hex chars, random order → sorts randomly\nULID advantage: natural chronological sorting + unique

Who Uses This Tool?

• Database designers choosing primary key formats for new applications
• Backend developers replacing UUID v4 for better database index performance
• Event sourcing and log systems where timestamp + uniqueness matters
• Distributed systems generating IDs without coordination between servers
• API developers using ULID as resource identifiers in REST endpoints

Pro Tips

• ULIDs are better than UUID v4 for database primary keys — the chronological sort reduces B-tree index fragmentation. But they're slightly larger (26 chars vs 36 for UUID with hyphens)
• For PostgreSQL, consider using UUID v7 (SQL:2023 standard, also time-sortable) if your PostgreSQL version supports it. ULID is a good alternative for application-level ID generation
• The 1ms timestamp granularity means two ULIDs generated in the same millisecond on different machines will still be unique due to the random component
• ULID is case-insensitive but conventionally uppercase. Our generator produces uppercase output matching the spec

Frequently Asked Questions about Ulid Generator

ULID vs UUID v7: which is better?

Both are time-sortable and 128-bit. UUID v7 is standardized (RFC 9562, 2024) and supported natively by some databases. ULID is simpler (just timestamp + random) and has a cleaner string representation (26 chars vs 36). For new projects, UUID v7 is the standards-track choice; ULID is the practical, simpler alternative.

Can ULIDs collide?

The 80-bit random component provides ~1.2 septillion (10^24) unique values per millisecond. The probability of collision within the same millisecond is astronomically low. Across different milliseconds, the timestamp guarantees uniqueness.

Free online Ulid Generator — no signup, 100% client-side processing. All data stays in your browser.