Everything in this category has the same hard requirement: the value must never leave the machine that made it. A password generated on someone else's server is a password that someone else has seen, and an identifier minted remotely is one more request that can fail. These tools draw from the browser random source and nothing is transmitted or stored — which also means a refreshed page cannot show you the same value twice, so copy it before you leave.
Tools in this category
Passphrase Generator
Build a passphrase from the EFF short wordlist — 1296 short words, about 10.3 bits each, drawn in your browser and never sent anywhere.
UUID Generator
Generate version 4 UUIDs in your browser, laid out exactly as RFC 9562 prescribes. Nothing leaves the page.
Password Generator
Generate a random password in your browser, with a length range taken from the NIST digital identity guidelines. Nothing is transmitted and nothing is stored.
Suggest a tool
Tell us what is missing and where its numbers should come from.
What should it convert, calculate or generate, and where would the authoritative numbers come from? A link to the standard or publication that defines them is the most useful thing you can send.
Opens your mail app with this page already filled in.
How these tools are built
Every tool in this category runs entirely in your browser: there is no upload, no account and no request to a server once the page has loaded. The numbers behind them are transcribed from the organisation that defines them — NIST for units, the W3C for web formats, the WHO for health measures — and each page names its source next to the formula. A tool whose reference values stop reproducing fails the build and does not ship, which is the whole reason the catalogue grows slowly.