UUID Generator
Generate random version-4 UUIDs in bulk, using your browser's cryptographic randomness. Nothing is sent anywhere.
About UUID Generator
UUID Generator creates version-4 universally unique identifiers using your browser's cryptographic random number generator. Generate one or a hundred at a time, with or without hyphens, in upper or lower case.
A UUID is a 128-bit value written as 32 hexadecimal digits, conventionally split into five hyphenated groups. Version 4 means almost all of those bits are simply random. The point is that two systems can each mint identifiers, with no coordination and no shared counter, and be safe in assuming they will never collide — which is what makes UUIDs the default primary key for anything distributed, anything offline-first, and anything where a client needs to name a record before the server has seen it.
The collision odds sound too good to be true, but the arithmetic is unforgiving in the right direction: with 122 random bits you would need to generate billions of UUIDs per second for a century before a duplicate became likely. In practice, collisions come from broken random number sources, not from probability. That is why generating them with a cryptographic source rather than a simple pseudo-random function actually matters.
The trade-off worth knowing is database behaviour. Random UUIDs scatter across an index rather than appending to the end of it, which fragments B-tree pages and can hurt insert performance on very large tables. Where that matters, teams reach for time-ordered variants such as UUIDv7, which keep the uniqueness guarantee while preserving rough sort order.
How to generate a UUID
- Choose how many UUIDs you need with the slider.
- Toggle hyphens off if your system expects a compact 32-character form.
- Toggle uppercase if your platform's convention requires it.
- Click Regenerate for a fresh batch at any time.
- Copy a single UUID, or copy the whole list at once.
Tips & common problems
Hyphens are formatting, not data
The identifier is the same 128 bits either way. Strip them if a schema wants a 32-character column, but stay consistent, because a hyphenated and an unhyphenated form of the same value will not compare as equal.
Case is not significant either
Hexadecimal is case-insensitive, so the same UUID may appear upper or lower case in different systems. Normalise on the way into a database so lookups do not silently miss.
Do not use a UUID as a secret
A v4 UUID is unpredictable but it is not a credential — they routinely appear in URLs and logs. Use a purpose-built token for anything that grants access.
Consider UUIDv7 for database keys
If these are becoming primary keys in a large table, a time-ordered variant keeps inserts sequential and avoids the index fragmentation that random UUIDs cause.
Frequently asked questions
What is a version 4 UUID?
A 128-bit identifier whose bits are essentially all random, apart from a few reserved to mark the version and variant. It is the most widely used UUID form because it needs no coordination between systems.
Can two generated UUIDs ever be the same?
In practice, no. With 122 random bits the probability is so small that a duplicate is far more likely to come from a faulty random source than from chance. This tool uses the browser's cryptographic generator.
Is a UUID the same thing as a GUID?
Yes. GUID is Microsoft's name for the same 128-bit identifier, and the two terms are used interchangeably. Formatting conventions occasionally differ, such as surrounding braces.
Are these UUIDs generated on your server?
No. They are generated in your browser and never transmitted. Reload the page and the previous batch is gone entirely.
Can I use a UUID as a password or API key?
No. UUIDs are designed to be unique, not secret, and they commonly end up in URLs, logs and analytics. Use a dedicated random token for authentication.
Why would I remove the hyphens?
Some databases and APIs store UUIDs as a plain 32-character string or as raw binary. Removing the hyphens matches that format — just apply the same convention everywhere.