Hey, great job on the website! I have one small criticism (in addition to others already listed here). I put in a song that was in the key of B. The most-used chords of this key are B, E, F#, and G#m - as I'm sure you're well aware. However, the songs chords were detected as B, E, F# and Abm. While technically correct, as Abm and G#m are the same chord, the convention is to list Abm as G#m in this case. I believe this is to avoid mixing sharps and flats in the written chords forms. Written chords should either all be in flats or sharps, rarely if ever mixed. Certain keys are listed with sharps, and others with flats. Here are the most common ones:
It was made in beeminder (https://www.beeminder.com/). It is a website where you pledge a certain amount of money towards a goal and if you don't stay on track, it charges you.
C - n/a
D - sharps
Eb - flats
E - sharps
F - flats
F# - sharps
G - sharps
Ab - flats
A - sharps
Bb - flats
B - sharps