This simple web app displays the chords containing a selected pitch. Click on a pitch anywhere to select that pitch (i.e. in the selector above, or anywhere you see a pitch below, e.g. in the spelling of a chord). The selected pitch is tinted in red. The keys q2w3er5t6y7u can be used like a keyboard (e.g. q=C, 2=C#, 5=F#, u=B) to select a note. The key # toggles between showing things in flats and sharps.
The keys z,x,c,v select: all chords; only triads; triads and 7ths; triads and sus.