How to tune with this tuner
Choose your instrument, press Start tuner and allow microphone access. Pluck one string and let it ring. The big letter shows the note you are playing and the needle shows how far off it is in cents (hundredths of a semitone). Needle on the left means flat, so tighten the string; needle on the right means sharp, so loosen it. When it is within 5 cents the display turns green.
Instrument presets
Guitar standard tuning is E A D G B E from the thickest string (E2 A2 D3 G3 B3 E4). Drop D lowers the sixth string to D2. Ukulele standard tuning is G C E A (G4 C4 E4 A4). Bass is E A D G, one octave below the guitar's lowest four strings, and violin is G D A E. In instrument mode the string closest to what you play is highlighted automatically. Chromatic mode shows any note, for wind instruments, voice or alternate tunings.
Tips for accurate tuning
Tune in a quiet room, hold your phone or laptop close to the instrument, and pluck firmly once instead of strumming. Tune up to the note from below, which helps the string hold its pitch. If you play with others, set the reference A4 to match them (440 Hz is standard; some orchestras use 442 Hz).