About ULID Generator

Use ULID Generator to Sortable unique IDs. The tool runs in your browser for fast results and keeps your data local.

How to Use

  1. 1. Add your input or data.
  2. 2. Adjust options if needed.
  3. 3. Review the result and copy it.

What is a ULID?

ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit identifier designed to combine the uniqueness of UUIDs with the sortability of timestamps. Unlike UUIDs, ULIDs are lexicographically sortable by creation time, making them ideal for database indexing and time-based queries. A ULID consists of a 48-bit timestamp (millisecond precision) followed by 80 bits of randomness, encoded as a 26-character case-insensitive string using Crockford Base32. ULIDs are URL-safe, monotonically increasing within the same millisecond, and have extremely low collision probability. They are particularly useful in distributed systems where you need unique identifiers that maintain chronological order without coordination between nodes.

Common Use Cases

ULIDs are ideal for distributed systems and databases that benefit from time-ordered identifiers. Database developers use ULIDs as primary keys in tables where chronological ordering improves query performance and reduces index fragmentation. Microservices architectures use ULIDs for request tracing and correlation across services without requiring centralized ID generation. Event sourcing systems use ULIDs to maintain event order while ensuring uniqueness across distributed event stores. API developers use ULIDs for resource identifiers that are both unique and reveal creation order. Log aggregation systems use ULIDs to correlate log entries across distributed services. NoSQL databases like MongoDB benefit from ULIDs as document IDs that improve range query performance.

  • Database primary keys with chronological ordering
  • Distributed request tracing and correlation IDs
  • Event sourcing and event store identifiers
  • API resource identifiers with time ordering
  • Log correlation across microservices
  • MongoDB document IDs for better range queries
  • Order IDs and transaction identifiers
  • Message queue and job identifiers

Best Practices & Tips

Use ULIDs instead of UUIDs when chronological ordering matters for your use case—the sortability improves database index performance. Store ULIDs as strings (26 characters) or binary (16 bytes) depending on your database—binary storage saves space but string storage is more readable. Ensure your ULID generation library uses cryptographically secure random number generation for the random component. In distributed systems, ULIDs generated on different nodes will still be roughly time-ordered, but exact ordering within the same millisecond is not guaranteed. Use ULIDs for new projects, but avoid migrating existing UUID-based systems unless the sortability benefit justifies the migration cost. Index ULID columns in databases to take advantage of their natural ordering.

  • Use ULIDs when chronological ordering improves performance
  • Store as 26-char string or 16-byte binary depending on needs
  • Ensure library uses cryptographically secure randomness
  • Index ULID columns in databases for optimal performance
  • Use for new projects rather than migrating from UUIDs
  • Understand that exact ordering within same millisecond varies
  • Prefer ULIDs over auto-increment IDs in distributed systems
  • Use ULIDs for correlation IDs in microservices

Troubleshooting Common Issues

If ULIDs are not sorting correctly, verify your database column is using string or binary comparison, not numeric. Clock skew between distributed nodes can cause ULIDs to appear out of order—use NTP to synchronize clocks. If you see duplicate ULIDs, check that your random number generator is properly seeded and cryptographically secure. Performance issues with ULID generation are rare but can occur if the random number generator is blocking—use non-blocking sources. When migrating from UUIDs to ULIDs, ensure your application code handles both formats during the transition period. If ULIDs are being truncated, verify your database column is at least 26 characters for string storage or 16 bytes for binary.

  • ULIDs not sorting correctly due to wrong column type
  • Clock skew causing out-of-order IDs in distributed systems
  • Duplicate ULIDs from weak random number generation
  • Performance issues with blocking random number generators
  • Migration challenges when transitioning from UUIDs
  • Truncated ULIDs due to insufficient column size
  • Confusion between string and binary storage formats

Frequently Asked Questions

Is ULID Generator free to use?

Yes. ULID Generator is free and works directly in your browser.

Does ULID Generator upload my data?

No. Most processing happens locally. Any network requests are clearly indicated.

What formats does ULID Generator support?

ULID Generator supports the common formats described on the page. Convert uncommon formats before pasting.

How should I share results from ULID Generator?

Copy the output and review any sensitive data before sharing or publishing.