About MultiKit
MultiKit is a growing collection of free online tools for developers and anyone who works with text, data and colors. Each tool runs in your browser, so what you type or paste stays on your device.
What makes a MultiKit page
Every tool page has the tool itself and the explanation people usually have to look for elsewhere:
- How to use it, in three steps.
- Worked examples, with real inputs and the exact results.
- How it works, including the rules and limits of the method, for example why a hash differs between tools or what a cron expression with both a day and a weekday means.
- Sources, linking to the standard or documentation the tool follows, such as an RFC, the Git manual or the WCAG guidelines.
- Frequently asked questions, answering what people actually get stuck on.
- The date of the last update.
How the tools are built and checked
The heavy lifting is done by well-known open-source libraries instead of home-made code: CodeMirror for the editors, jose for JSON Web Tokens, cron-parser and cronstrue for cron expressions, sql-formatter for SQL, yaml for YAML, culori for colors, node-qrcode for QR codes, node-diff3 for three-way merging and hash-wasm for MD5. Each library’s name and link appear on the pages that use it.
The logic of every tool is covered by automated tests. Where a published reference exists, the tests use it: the standard test vectors for MD5 and the SHA family, the sample token from jwt.io, the WCAG contrast formula, and the documented behaviour of cron and YAML. A tool is published only when its examples on the page match what the tool actually produces.
What we do not do
- We do not ask you to create an account.
- We do not send what you type, paste or open to a server. Tool inputs are processed in your browser.
- We do not set cookies or run analytics of our own. The site is supported by Google AdSense advertising, which is a separate service that may use cookies; see the Privacy Policy.
- We do not give legal, financial or security advice. Results are for convenience, and important values should be checked.
Corrections and suggestions
If a result looks wrong, contact us with the tool name, the input you used and the result you expected. A wrong result is treated as a bug, and the page and its tests are fixed. Suggestions for new tools are welcome in the same way.