UUID generator
Version 4 UUIDs, generated on this page from your browser's own cryptographic randomness.
Nothing is stored and nothing repeats: reload and you get a different set.
Version 4, from your browser's own cryptographic randomness rather than from Math.random, which is a fast sequence and not a random source. Between 1 and 100 at a time.
- Generating.
Questions
- Is what I paste sent anywhere?
- No. Every tool in this kit runs in the page itself. There is no server here that receives what you paste, and you can check it in your browser's network tab: using a tool produces no request carrying your input at all.
- Where does the randomness come from?
- From crypto.getRandomValues, which is the browser's cryptographic random source. Not Math.random, which is a fast sequence rather than a random source: values from it can collide and can be predicted from earlier ones.
- What makes it version 4?
- Two fixed pieces among the random bits: a 4 in one position marking the version, and two bits in another marking the RFC 4122 variant. Without them it is 128 random bits that no parser will agree is a v4 UUID. Both are set here.
- Could two of these ever be the same?
- In principle, and not in practice. There are 122 random bits, so you would need to generate billions per second for a lifetime before a collision became likely.
The other tools here
- JSON formatter, format, minify and validate
- Base64 encoder, encode and decode, text or file
- URL encoder, encode and decode, two rules
- Hash generator, sha-256, sha-1 and md5 at once
- JWT decoder, header, payload and expiry
- Regex tester, live matches, groups and flags
- Text diff, compare two blocks, by line or word
- Timestamp converter, unix time to a date, and back
- Cron explainer, a schedule, in plain english
- Colour converter, hex, rgb, hsl, and a contrast check
- Markdown preview, live preview, and copy the html
- JSON to CSV, an array of objects into a spreadsheet