Centerline: Guitar Tuner

Open it and pluck a string. The large meter tells you exactly which way to turn.

Four ways to read the same pitch, switchable at any time and without replucking: Simple, the note and one line. Strobe, drifting bars that stand still the moment you are in tune. All strings, one row per string so you can see which ones you have already done. Guitar, the six-string diagram.

Standard tuning is free forever, with automatic string detection and every display. One purchase unlocks Drop D, Half step down, D standard, DADGAD, Open G, and the A4 reference. Pay once. No subscription.

Your microphone audio stays on your device and disappears as it is analyzed. There is no account, no ads, no trackers, and no Internet access of any kind: the app never asks for the network permission.