UUID Generator
Generate one or more random version-4 UUIDs. Options for uppercase and hyphen removal.
How It Works
The UUID Generator produces RFC 4122-compliant universally unique identifiers in your browser. Choose UUID version 4 (random, the modern default — 122 bits of randomness, with collision probability negligible even after generating billions of identifiers) or version 1 (time- and MAC-based — preserves chronological order, less common today because it leaks the host MAC address), select how many to generate at once (from 1 to several thousand), and click Generate. The tool uses crypto.getRandomValues for the random bits, ensuring statistical uniqueness, and formats the output in the canonical 8-4-4-4-12 hyphenated lowercase form (xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx) that databases, APIs, and configuration files universally accept. UUID v4 is the right default for almost every use case: distributed-system event IDs, database primary keys when natural keys do not exist, request correlation IDs for tracing, and unique identifiers for test fixtures. Generation is instant and runs entirely client-side; the UUIDs you produce are not stored or transmitted, so even identifiers used in production systems stay confidential.
Use Cases
- Generating primary keys for database records
- Creating unique identifiers for distributed system events
- Producing test GUIDs for unit tests
- Generating correlation IDs for request tracing
Frequently Asked Questions
- Should I use v4 or v1?
- v4 for almost every use. v1 is mostly historical — it embeds a timestamp and (originally) the host MAC address, which leaks information you usually do not want to share.
- How unique is a v4 UUID?
- The collision probability is negligible at any practical scale. You can generate a billion UUIDs and the probability of any duplicate is around 10^−18.
- Are these cryptographically random?
- Yes — the 122 random bits come from crypto.getRandomValues, the same source used for TLS keys. They are unguessable by an attacker.
- Why do all my v4 UUIDs have a 4 in the third group?
- That is the version field — the 13th hex digit is fixed at 4 to mark these as version 4 random UUIDs, per RFC 4122.
- Are the generated UUIDs sent anywhere?
- No. They are produced in your browser and exist only in the current page.