ULID (Universally Unique Lexicographically Sortable Identifier) is a 26-character string format that combines a timestamp with random data to create identifiers that are both unique and sortable by creation time. ULIDs are an alternative to UUIDs with better sorting capabilities.

Why use ULIDs instead of UUIDs?

ULIDs offer several advantages over UUIDs: they are lexicographically sortable by generation time, they use a more compact representation (26 characters vs 36 for UUIDs), they're case-insensitive, and they avoid problematic characters like hyphens.

How do I convert a UUID to a ULID?

You can convert a UUID to a ULID using our UUID Converter tool. Simply paste your UUID into the input field and click Convert. The tool supports UUID v1, v4, v7, and any hex string, converting them losslessly to ULID format and back.

Can I decode a ULID to see its timestamp?

Yes, you can decode a ULID using our ULID Decoder tool. It will show you the timestamp in various formats (Unix timestamp, ISO string, human-readable date) and the random component in different representations.

Are ULIDs suitable for database primary keys?

Yes, ULIDs are excellent for database primary keys. They're sortable by creation time which improves database performance, they're URL-safe, and they can be generated without a central coordinator, making them ideal for distributed systems.

What is NanoID and when should I use it?

NanoID is a tiny, secure, URL-friendly unique string ID generator. It's smaller and faster than UUID and is ideal for generating short unique IDs for URLs, session tokens, or any situation where a compact random identifier is needed. Unlike ULID, NanoID is not time-sortable.

What is a Snowflake ID?

Snowflake ID is a 64-bit unique identifier format originally developed by Twitter. It encodes a timestamp, datacenter ID, machine ID, and sequence number. Snowflake IDs are sortable by time, extremely fast to generate, and widely used in distributed systems like Twitter, Discord, and Instagram.

How do I decode a JWT token?

Paste your JWT token into our JWT Decoder tool to instantly see the decoded header, payload, and signature. The tool shows all claims including expiry time (exp), issued-at (iat), and custom claims. No data is sent to any server - decoding is done entirely in your browser.

What is CUID and CUID2?

CUID (Collision-resistant Unique Identifier) is designed for horizontal scalability and sequential IDs for databases and distributed systems. CUID2 is the improved next generation with better security and randomness properties. Both are excellent alternatives to UUID for Node.js applications.

DB Insert Benchmark

DB Insert Benchmark - free online developer tool. 100% client-side: your data never leaves your browser.

Database Index Insertion Benchmark

Compare database index writing performance between Sequential IDs (ULIDs / UUID v7) and Random IDs (UUID v4) using IndexedDB.

Insertion Batch Size (Number of IDs)

Time-Sorted Sequential IDs (ULID / UUID v7)

Idle

Total Time:—

Avg Write Speed:—

Unsorted Random IDs (UUID v4)

Idle

Total Time:—

Avg Write Speed:—

Index Insertion Cost Curve

This graph plots transaction latency (ms) for consecutive database insert operations. Notice how random inserts trigger B-Tree page splits, causing latency spikes.

No data yet. Run the benchmark to plot results.

Sequential (ULID / UUID v7)

Random (UUID v4)

Why is there a performance difference?

Modern databases (such as IndexedDB, SQLite, PostgreSQL, and MySQL) store primary keys inside a B-Tree or B+Tree index structure. When you insert sequential IDs (ULIDs, UUID v7), new records are always appended to the right-most edge of the index, requiring zero re-balancing. In contrast, random IDs (UUID v4) must be inserted at arbitrary nodes, forcing the database to frequently split data pages, move physical sectors, and fragment the index, resulting in slow writes and high storage space overhead.

ULID Generator

Free Online Developer Tools - ULID, UUID, NanoID, CUID, Snowflake ID, JWT Decoder, Base64, JSON Formatter & More