UUID Generator
Generate universally unique identifiers (UUIDs) one at a time or in bulk, ready to drop into databases, code, or test data. The values are created in your browser using a strong random source.
UUID v4 Generator
Generate one or more random UUIDs and quickly copy or download them for use in your projects.
Min 1 • Max 100
What a UUID guarantees
A UUID is a 128-bit identifier written as 36 characters with hyphens, like 550e8400-e29b-41d4-a716-446655440000. Its purpose is to let independent systems create IDs that will not collide without coordinating with each other. A version 4 UUID is almost entirely random, and the space is so large that the practical chance of two colliding is effectively zero.
This is why distributed systems love them: a client, a server, and a queue can each mint IDs offline and still be confident they are unique when the data merges.
When to use one (and when not to)
UUIDs are ideal as keys you generate anywhere, but they have trade-offs.
- Great for primary keys you must create before talking to the database, and for idempotency keys.
- Avoid exposing sequential database IDs in URLs - a UUID leaks no count and is hard to guess.
- They are larger and less index-friendly than integers, so weigh that for very high-volume tables.
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FAQs
Are these UUIDs guaranteed to be unique?▼
Not absolutely, but the probability of a collision among version 4 UUIDs is so small it is ignored in practice. You would need to generate billions of them before a collision became even remotely likely.
Which UUID version does this generate?▼
It generates version 4 UUIDs, which are randomly generated. Version 4 is the most common choice when you simply need a unique value and do not need time or hardware information embedded.
Are they generated securely in my browser?▼
Yes. They use the browser's cryptographic random source, and generation is local - nothing is sent to a server. That makes them safe to use as real identifiers.
Can I use a UUID as a database primary key?▼
Yes, and it is common in distributed systems because you can create the key before inserting the row. The trade-off is that UUIDs are larger than integers and can fragment indexes; some teams use ordered UUID variants to reduce that.
What is the difference between UUID v1 and v4?▼
v1 is based on timestamp and machine identity, so it is time-ordered but can leak when and where it was made. v4 is random, leaking nothing but with no ordering. This tool produces v4.
Are UUIDs case sensitive?▼
By specification they are case-insensitive, and they are conventionally written in lowercase. Treat 'A' and 'a' as the same when comparing, but store them consistently to avoid confusion.
Can I generate many at once?▼
Yes, you can produce them in bulk for seeding test data or pre-allocating keys. Each one is independently random.
Is it safe to put a UUID in a public URL?▼
Yes. A v4 UUID reveals no sequence and is effectively unguessable, so it does not leak how many records you have the way an incrementing integer ID does. It is not a secret, though, so still protect the resource with proper access control.
Why are there hyphens, and can I remove them?▼
The hyphens split the 32 hex digits into the canonical 8-4-4-4-12 grouping for readability. You can strip them for storage if your system expects a 32-character form, as long as you are consistent.
Do UUIDs ever need to be regenerated?▼
No. Once assigned, a UUID is a permanent identifier for that record. Regenerating it would break references. You only create a new one for a new entity.
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