The slider is logarithmic, like human pitch perception, so low, mid, and high frequencies are all easy to dial in precisely.

Sine gives the purest tone for hearing tests; square, triangle, and sawtooth add harmonics for testing speakers and finding rattles.

Glide smoothly from low to high (or reverse) over up to 120 seconds, with a live readout of the current frequency as the sweep plays.

One-tap jumps to 20 Hz, 200 Hz, 1 kHz, 10 kHz, and 20 kHz — the anchor points of the audible spectrum.

Watch the actual shape of the tone as it plays, so you can see the difference each waveform makes, not just hear it.

Every tone is generated sample-by-sample by the Web Audio API on your device — no audio files, no streaming, no latency.