Generate a random UUID v4 in the browser

UUID v4 is 122 random bits plus a version nibble. Collision risk is negligible for app IDs. The string looks like 550e8400-e29b-41d4-a716-446655440000; the 13th hex digit is 4.

Use v4 when you do not need time order: client-side IDs, test fixtures, request correlation. For database primary keys that you want to sort by insert time, use UUID v7 on the sibling page.

Generation uses the Web Crypto RNG. Nothing is logged. Batch copy is for seed data. Do not treat a UUID as a secret; it is an identifier, not a password.

Version 4 puts 4 in the version nibble and a 8, 9, a, or b in the variant nibble. The other 122 bits are random. A fresh id does not sort by time and does not say which machine made it. Collisions are not a practical worry at human scale; they are a worry if a broken generator returns the same value twice. The nil UUID is all zeros and is not a v4. This page opens on version 4. Version 7, which encodes milliseconds, is the other converter.