19 essential developer tools in a Chrome side panel — JSON Formatter, JWT Decoder, Base64, Regex Tester, Diff Checker, UUID Generator, Cron Builder, and more. No more juggling bookmarks or hopping between jsonformatter.org, jwt.io, and diffchecker.com. Everything runs offline in your browser, no data leaves your machine, no accounts. Toggle with Ctrl+Shift+D. Free forever, open source utility lib.