Browser extension. Various formulas and tools that are useful for homebrewer.
Firefox: https://addons.mozilla.org/en-GB/firefox/addon/brewy/
Chrome: https://chrome.google.com/webstore/detail/brewy/dajahhjocjpandlbdhgpnfgndnoemnip
I write about in https://www.erlend.ee/blog/how-write-your-own-homebrewer-tool-extension-firefox-or-chrome