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Free UUID Generator

A browser-based UUID generator that creates RFC 9562-compliant identifiers. Choose between v4 (random) for general-purpose unique IDs and v7 (time-ordered) for sortable database-friendly IDs. Generate up to 100 UUIDs at once with configurable uppercase/lowercase and hyphen formatting. All generation uses the browser's cryptographic random number generator — no data is sent anywhere.

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What is UUID Generator?

A browser-based UUID generator that creates RFC 9562-compliant identifiers. Choose between v4 (random) for general-purpose unique IDs and v7 (time-ordered) for sortable database-friendly IDs. Generate up to 100 UUIDs at once with configurable uppercase/lowercase and hyphen formatting. All generation uses the browser's cryptographic random number generator — no data is sent anywhere.

quickAnswer

Generate UUID v4 (random) or v7 (time-sortable) identifiers. Choose count, case, and hyphen format. Uses crypto.randomUUID() — secure and local.

Last updated: 2026-06-08

limitations

  • UUID v7 has lower uniqueness guarantees than v4 in the same millisecond because part of the ID is deterministic (timestamp). If you generate many IDs in the same millisecond, add a counter or use v4.
  • Generating more than 100 UUIDs at once may briefly block the browser UI thread. For larger batches, generate in chunks.
  • UUIDs are 36 characters with hyphens (32 without) — they consume more storage than auto-incrementing integers. Consider this for high-volume database applications.

Sources:MDN Web Docs · W3C Specifications · jquery.app on GitHub

How to use this tool

  1. Choose UUID version: v4 for general use, v7 for time-ordered (database-friendly) IDs.
  2. Set the number of UUIDs to generate (1-100).
  3. Toggle uppercase and hyphen options as needed.
  4. Copy individual UUIDs or the full list for use in your project.

What you can use it for

  • Generate a unique ID for a new database record before inserting it.
  • Create a batch of unique identifiers for test data or seed files.
  • Generate a v7 UUID for a database primary key that sorts chronologically.

Use cases

Practical examples

example

Database primary key generation

A developer needs a unique primary key for a new user record. They generate a v7 UUID that includes a timestamp component, making it sortable in the database index without a separate created_at column.

example

Batch test data creation

A QA engineer needs 50 unique IDs for test fixtures. They generate 50 v4 UUIDs in one click, copy the list, and paste it into the test data file.

Common mistakes

  • Using v4 UUIDs as database primary keys in large tables — the random ordering causes index fragmentation. Use v7 for database-friendly time-sorted keys.
  • Stripping hyphens from UUIDs without documenting the format — downstream systems may expect the standard 8-4-4-4-12 format.
  • Assuming UUIDs are guaranteed unique — collisions are astronomically unlikely with v4 but theoretically possible. For critical systems, add application-level uniqueness checks.

verification

  1. Generate a v4 UUID and verify it matches the format xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx (version nibble is 4).
  2. Generate a v7 UUID and verify the first segment changes when generated a few seconds apart (time-ordering).

FAQ

Questions about UUID Generator

What is the difference between UUID v4 and v7?

UUID v4 is fully random — every bit except the version and variant bits is randomly generated. It provides maximum uniqueness but does not sort chronologically. UUID v7 includes a Unix timestamp in the first 48 bits, making it sortable by creation time. Use v4 for general-purpose IDs. Use v7 for database primary keys where time-based sorting improves index performance.

Are these UUIDs cryptographically secure?

Yes. v4 UUIDs use crypto.randomUUID() which relies on the browser's cryptographic random number generator (CSPRNG). The output is suitable for use as session tokens, API keys, and other security-sensitive identifiers where unpredictability matters.

How likely is a UUID collision?

For v4 UUIDs, the probability of collision is approximately 1 in 2^122 (about 5.3 undecillion). You would need to generate 1 billion UUIDs per second for about 100 years to have a 50% chance of a single collision. For practical purposes, v4 UUIDs can be treated as unique.

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