What is Uuid Generator
The UUID Generator creates universally unique identifiers in two formats: UUID v4 (a 128-bit random number displayed as 32 hexadecimal characters with hyphens in the standard 8-4-4-4-12 layout) and ULID (Universally Unique Lexicographically Sortable Identifier, a 128-bit value that encodes the current timestamp in the first 10 characters followed by 26 random characters in Crockford's Base32 alphabet). Both formats produce identifiers that are practically guaranteed to be unique across all devices and all time, without requiring coordination between systems.
How to Use Uuid Generator
- Select the identifier format from the dropdown — UUID v4 for standard random identifiers, ULID for time-sortable identifiers.
- Set the count — generate between 1 and 1000 identifiers at once. ULIDs are particularly useful for database primary keys because they sort chronologically.
- Choose the case — lowercase (default) or UPPERCASE. Some systems require uppercase UUIDs in HTTP headers.
- Click Generate to produce the identifiers. Each run produces cryptographically random values using the Web Crypto API's crypto.getRandomValues().
- Copy the output — each identifier is on its own line. For single identifiers, use the copy button; for batches, the entire list is copied at once.
Why Use Uuid Generator
UUIDs and ULIDs solve the distributed systems problem of generating unique identifiers without a central authority. When multiple servers, microservices, or offline clients need to create records independently, they can each generate UUIDs locally with zero coordination and be confident the IDs will never collide. UUID v4 is the most common format — it's what most databases, APIs, and message queues expect. ULIDs add a time-sorting advantage: they lexicographically sort in creation order, making them ideal for database primary keys where insertion order matters. The ULID timestamp portion uses millisecond precision, so you can extract the creation time from the identifier itself.
Privacy & Security
This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.
Frequently Asked Questions
What's the difference between UUID v4 and ULID?
UUID v4 is 128 bits of pure randomness (version 4 indicates random generation). ULID splits the 128 bits into a 48-bit millisecond timestamp and 80 bits of randomness. ULIDs sort chronologically when sorted as strings; UUIDs do not. UUID v4 is the industry standard (RFC 4122); ULID is newer and preferred for database keys where insertion order matters.
Can two UUID v4 values ever collide?
The probability of collision for UUID v4 is approximately 2^-122 (about 1 in 5.3 × 10^36). This is so small that you could generate 1 billion UUIDs per second for 85 years and still have only a 50% chance of a single collision. For practical purposes, UUID v4 collisions never happen.
Why use ULID instead of auto-incrementing integers?
Auto-incrementing integers require a central counter, which becomes a bottleneck in distributed systems. ULIDs can be generated independently by any node without coordination. They also encode creation time (extractable from the first 10 characters), which is useful for debugging and audit logs. The tradeoff is larger storage (16 bytes vs 4-8 bytes for an integer) and less human-readable values.
Is this compatible with databases?
Yes. UUID v4 works as a primary key in PostgreSQL (uuid type), MySQL (CHAR(36) or BINARY(16)), MongoDB (stored natively), and most ORMs. ULIDs can be stored as strings or converted to 128-bit integers. Some databases have native ULID support or extensions.