ULID Generator
Generate secure, sortable ULIDs with batch and formatting options.
ULID Generator
Create sortable ULIDs in bulk with formatting options.
About ULID Generator
ULID Generator (Universally Unique Lexicographically Sortable Identifier)
Generate secure, sortable ULIDs in seconds. A ULID looks similar to a short code, but it is designed for serious systems: it keeps the convenience of a UUID while adding chronological sortability. Use this tool to create one or many ULIDs for databases, APIs, event logs, queues, and distributed services.
This ULID Generator creates valid 26-character Crockford Base32 identifiers with millisecond timestamps and strong randomness. You can generate batches, switch between uppercase and lowercase, and export results for immediate use in your project.
How It Works
A ULID is a 128-bit identifier split into two parts: a 48-bit timestamp (milliseconds since the Unix epoch) and an 80-bit random component. The timestamp makes ULIDs naturally sortable by creation time, while the random part provides uniqueness even when many IDs are created in the same millisecond.
Generation steps
- 1) Timestamp: The tool captures the current time in milliseconds and encodes it into the first 10 Base32 characters.
- 2) Randomness: It then generates 80 bits of cryptographically strong randomness and encodes it into the remaining 16 characters.
- 3) Encoding: The full 128-bit value is encoded using Crockford Base32, producing a 26-character ULID that avoids confusing characters.
- 4) Formatting: Optional formatting can group characters with hyphens for readability, and you can switch output casing.
Because the timestamp comes first, sorting ULIDs as strings typically sorts them by creation time. That makes ULIDs convenient for ordered primary keys, append-only logs, and data pipelines.
Key Features
Batch generation
Create a single ULID or generate hundreds at once for test data, migrations, fixtures, or load testing. Each generated ID remains valid and independent.
Sortable by time
Unlike random UUIDs, ULIDs are lexicographically sortable because the timestamp is encoded first. This property is useful for pagination, cursor-based APIs, and time-series workloads.
Case and grouping options
Choose uppercase (common for Crockford Base32) or lowercase to match your code style. You can also group output with hyphens to make IDs easier to read aloud or review in logs.
Copy and download
Copy the generated list with one click or download it as a plain text file. This is ideal when you need to paste IDs into SQL scripts, JSON fixtures, or configuration files.
Safe defaults
The generator is built around secure randomness, sensible limits, and clear validation so it works reliably on first load and stays predictable under heavy use.
Use Cases
- Database primary keys: Use ULIDs as string primary keys that maintain insertion order, reducing index fragmentation compared to fully random identifiers.
- Event sourcing and logs: Produce event IDs that sort by time for easy replay and debugging.
- API resources: Provide non-sequential public identifiers that are hard to guess but still support chronological listing.
- Queues and message brokers: Tag messages with sortable IDs to track processing order across services.
- Testing and fixtures: Generate large batches of realistic identifiers for unit tests, integration tests, and demos.
- File naming: Create collision-resistant file names that keep natural time order in directories and object storage.
In short: whenever you need unique identifiers that behave well in sorted lists, ULIDs are an excellent upgrade over purely random tokens.
Optimization Tips
Choose a consistent casing
Pick uppercase or lowercase and use it everywhere. This avoids subtle duplicates in case-insensitive systems and makes searching more consistent in dashboards and logs.
Use plain format for storage
Hyphen grouping is great for humans, but for storage and comparisons the plain 26-character ULID is simpler. If you need grouping, consider applying it only in UI output.
Think about indexing
In relational databases, ULIDs often improve index locality compared to UUIDv4. For best performance, store ULIDs in a fixed-length column (like CHAR(26)) and index it. In document stores, store as a string and rely on the natural sort order.
Frequently Asked Questions
ULIDs are especially popular in distributed systems because they behave predictably under concurrency. When many services write data at the same time, purely sequential IDs can become a bottleneck and purely random IDs can make indexes jump around. ULIDs strike a middle ground: the timestamp keeps inserts roughly ordered, and the random portion prevents guessability and collisions. This is helpful for multi-tenant SaaS products, analytics pipelines, audit trails, and any architecture where multiple producers generate IDs independently.
Another advantage is ergonomics. A 26-character ULID is shorter than the common UUID string representation and is URL-safe without additional encoding. You can embed it in REST paths, GraphQL nodes, webhook payloads, or client-side state without worrying about special characters. Because the format is fixed-length, it is easy to validate and to recognize in logs. When you need to track an incident, you can search for a ULID prefix to quickly narrow down all records created during a specific time window.
If you are migrating from UUIDs, you can often adopt ULIDs incrementally. Start by generating ULIDs for new records while keeping existing UUIDs untouched, or store ULIDs as an additional external identifier. Over time, you can move consumers to the new scheme. Many libraries in different languages support ULID parsing and generation, but for quick tasks—like creating a few IDs for a migration script—an online generator is the fastest solution.
Why Choose This Tool
This ULID Generator is built for real workflows: it loads with sensible defaults, generates valid identifiers using secure randomness, and presents results in a clean, copy-friendly layout. The interface is designed to help you move fast—from the first page load to a ready-to-use list of IDs.
Whether you are designing a new database schema, building an API, or preparing test data, ULIDs provide a practical balance between uniqueness, security, and sortability. Use this tool to standardize identifier generation across your team and keep your systems clean, scalable, and easy to debug.
ULIDs are especially popular in distributed systems because they behave predictably under concurrency. When many services write data at the same time, purely sequential IDs can become a bottleneck and purely random IDs can make indexes jump around. ULIDs strike a middle ground: the timestamp keeps inserts roughly ordered, and the random portion prevents guessability and collisions. This is helpful for multi-tenant SaaS products, analytics pipelines, audit trails, and any architecture where multiple producers generate IDs independently.
Another advantage is ergonomics. A 26-character ULID is shorter than the common UUID string representation and is URL-safe without additional encoding. You can embed it in REST paths, GraphQL nodes, webhook payloads, or client-side state without worrying about special characters. Because the format is fixed-length, it is easy to validate and to recognize in logs. When you need to track an incident, you can search for a ULID prefix to quickly narrow down all records created during a specific time window.
If you are migrating from UUIDs, you can often adopt ULIDs incrementally. Start by generating ULIDs for new records while keeping existing UUIDs untouched, or store ULIDs as an additional external identifier. Over time, you can move consumers to the new scheme. Many libraries in different languages support ULID parsing and generation, but for quick tasks—like creating a few IDs for a migration script—an online generator is the fastest solution.