HertzKit is a collection of free, browser-based audio utilities designed for musicians, producers, and audio enthusiasts. Its flagship Online Tone Generator supports sine, square, sawtooth, and triangle waves from 1Hz to 20kHz+. It features an intuitive, ad-light interface perfect for testing subwoofers, calibrating sound systems, running frequency sweeps, or even safely removing dust and water from mobile speakers. No installation or registration required - just pure web audio.