How to use
- 1Choose v4 (random) or v7 (time-ordered).
- 2Set how many to generate (1–1,000) and the format: uppercase, braces or no hyphens.
- 3Copy the list or download it as uuids.txt.
- 4Paste any UUID into the validator to check it and read its version, variant and embedded time.
UUID v4 vs. v7
A UUID is a 128-bit identifier written as 32 hex digits in the 8-4-4-4-12 pattern. Version 4 fills 122 of those bits with random data from your browser’s cryptographically secure generator (crypto.randomUUID), so collisions are practically impossible. Version 7, standardized in RFC 9562 (2024), starts with a 48-bit Unix timestamp in milliseconds followed by random bits, so IDs sort by creation time. That makes v7 the better primary key for databases such as PostgreSQL and MySQL: new rows are appended at the end of the B-tree index instead of landing at random positions. This generator also keeps v7 IDs strictly increasing within the same millisecond using a 12-bit counter (RFC 9562, method 1).
Decoding and validating a UUID
The validator accepts UUIDs with or without hyphens, wrapped in braces or with a urn:uuid: prefix. It reads the version from the 13th hex digit and the variant from the 17th, and for v1, v6 and v7 extracts the embedded timestamp, shown as a local date, an ISO 8601 UTC value and Unix milliseconds. For v1 and v6 it also shows the clock sequence and the node field, which older implementations filled with the generating machine’s MAC address. The special nil UUID (all zeros) and max UUID (all Fs) are recognized too.
Formats and privacy
Uppercase output suits tools that expect it, braces match the {GUID} style used in the Windows registry and .NET, and the no-hyphen option gives a compact 32-character form for URLs or file names. UUIDs are created locally in your browser; nothing is sent to a server or logged. Keep in mind that a v7 UUID reveals when it was created, so use v4 when the creation time should stay private.
Frequently asked questions
Are UUIDs really unique?
For practical purposes, yes. With 122 random bits you would need to generate about 2.7 quintillion v4 UUIDs to reach a 50% chance of a single collision.
What is the difference between a UUID and a GUID?
None in practice: GUID is Microsoft’s name for the same 128-bit identifier. GUIDs are often written in uppercase and wrapped in braces.
Should I use UUID v7 for database keys?
It is usually a good choice: v7 IDs are time-ordered, which keeps B-tree indexes compact and inserts fast, while staying globally unique without coordination.
Can I use a UUID as a secret token?
A v4 UUID is random, but UUIDs are designed as identifiers, not secrets. For session tokens or password-reset links, use your framework’s dedicated secure token generator.
Not happy with the results?
Talk to Webin Agency about fast, SEO-friendly websites, e-commerce and Google Ads management.