What Is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit value, usually written as xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, designed so that two randomly generated UUIDs are essentially guaranteed never to collide. They're used everywhere — database primary keys, session tokens, file names, distributed system IDs.
UUID v4 specifically is generated using random numbers, making it the simplest and most common variant for general-purpose unique IDs.
What Is a Hash?
A hash function takes any input (text, a file, anything) and produces a fixed-length string — a "fingerprint." The same input always produces the same hash, but you can't reverse a hash back into the original input. Common algorithms:
| Algorithm | Output length | Common use |
|---|---|---|
| MD5 | 128-bit | Checksums, legacy systems (not secure for passwords) |
| SHA-1 | 160-bit | Git commit IDs, legacy checksums |
| SHA-256 | 256-bit | Modern security, blockchain, certificates |
| SHA-512 | 512-bit | High-security applications |
How to Generate UUIDs and Hashes for Free
A Word of Caution
MD5 and SHA-1 are not safe for storing passwords — they're fast to compute, which makes them easy to brute-force. For password storage, use a dedicated algorithm like bcrypt or Argon2 in your application code. This tool is best for checksums, cache-busting, deduplication, and general-purpose unique IDs.
Frequently Asked Questions
Is it safe to hash sensitive data with this tool?
All hashing happens locally in your browser via the Web Crypto API (and a local MD5 implementation) — your text never leaves your device.
What's the chance two UUID v4s collide?
Astronomically small — about 1 in 2.71 quintillion for any two randomly generated UUID v4s.
Can I generate more than 50 UUIDs at once?
The tool currently supports up to 50 per batch — simply run it again for more.
Related Tools
You might also find the Base64 Encoder/Decoder and JWT Decoder useful for related developer tasks.