TONOS

TONOS is a tone generator that works right in your browser: no install needed, open the page, hit PLAY, and you hear a clean pure tone. It is handy for tuning, testing speakers, tuning an instrument, or just finding out what 440Hz actually sounds like.

The controls are practical: four waveforms (sine, square, triangle, sawtooth), frequencies from 20Hz to 20kHz, typed in directly or moved with a log slider, semitone steps, or octave jumps; you can also pick by note name, and the A4 reference can be set anywhere from 400 to 480Hz. Volume is shown clearly in dBFS, and output can go to the left channel or the right channel only, which makes checking speaker wiring easy.

It also comes with an oscilloscope that behaves like a real instrument: a stable triggered display, adjustable range and timebase, and at high frequencies it reconstructs the waveform with sinc interpolation instead of joining the dots with straight lines; the volume slider is a hard limit, so even pushed to 0dBFS it will not clip, and if trimming kicks in it tells you straight away how much was squeezed.

One thing to be clear about: this is a single-page tool with no account and no cloud, and your last settings live only in your own browser; the whole project is plain HTML, CSS and JavaScript with no dependencies, so you can download the published package and host it on any static server for offline use. It has only 2 stars on GitHub and is just getting started, so do not expect a community or customer support.