UUID Generator — by BitTools

A UUID (Universally Unique Identifier) is a 128-bit identifier commonly displayed as a 36-character string (8-4-4-4-12). UUID v4 uses cryptographically-strong random values for most bits and is ideal when you need decentralized, collision-resistant IDs without a central server.

How to use the UUID Generator

1. Open the generator page (UUID Generator).
2. Choose how many UUIDs you want to generate (you can generate multiple at once).
3. Click Generate to create RFC-4122 UUID v4 values using your browser's crypto API.
4. Use Copy to copy the list to clipboard or Download to save them as a text file.

Examples

Single UUID (v4)

      f47ac10b-58cc-4372-a567-0e02b2c3d479
            

Multiple UUIDs (sample)

      d9b1c36e-9d3b-4a11-9b2f-2a9f1d1e8c3c
      9f8b6d2c-4a72-4c1a-8f3e-1b2a3c4d5e6f
      2a4b6c8d-7e9f-4a01-b2c3-9d8e7f6a5b4c
            

Best practices

• Use UUID v4 for decentralised ID generation: Generate IDs client-side or in microservices without coordination.
• Store as binary when possible: In databases, store UUID as a 16-byte binary to save space and improve indexing.
• Prefer canonical lowercase: Use the standard lowercase, hyphenated representation (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx).
• Don't rely on UUIDs as secrets: UUID v4 is random but not intended for authentication tokens; use secure secrets for that.
• Validate input: When accepting UUIDs from users or APIs, validate format and version (version 4) to avoid malformed data.

Common pitfalls

• Assuming UUIDs are cryptographically unguessable — they're random but not a substitute for secrets.
• Using string UUIDs in high-write DB indexes without considering UUID ordering (random v4 can fragment B-tree indexes).
• Double-encoding or altering hyphens when storing/retrieving across systems.
• Generating UUIDs with non-cryptographic RNGs (use crypto.getRandomValues in browsers or secure RNG on servers).

FAQ

Does the tool upload my data?

No. UUIDs are generated locally in your browser using the Web Crypto API; nothing is sent to the server.

What's the difference between UUID v1 and v4?

v1 embeds timestamp and node (MAC) information — it can leak timing/location details. v4 is random and preferred when privacy and decentralization matter.

Should I use UUIDs as database primary keys?

Yes, in many distributed systems. But consider index performance: use UUIDv4 with strategies like UUIDv6/ULID or ordered UUIDs if sequential-ish insertion helps DB performance.

Try the tool: UUID v4 Generator