About
ChordFrog trains you to recognise chords by ear, and you can try it in the browser with nothing to install.
Hear a real grand-piano chord and name it from four options. Ten questions to a round, three tries each, scored out of 100. Every option shares a root, so what is being tested is the chord's quality rather than the note it starts on.
Connect a MIDI keyboard and it names whatever you play in real time, inversions and slash chords included, plus seventh chords voiced without their fifth - which is how people actually play them. Web MIDI works in Chrome, Edge and Firefox; Safari does not implement it, so on iPhone and iPad the listening drill is the whole experience.
There is also a free iOS app that does MIDI natively over USB or Bluetooth, with five progressive levels, six practice modes and a screen tracking which chords still beat you. Free and ad-supported, nothing behind a paywall.