An online quad equalizer runs entirely in your web browser, so there is nothing to install and nothing to configure before you start shaping sound.
Running the equalizer online means the same tool works identically on a laptop, a school computer, or a borrowed machine — your settings live in the page, not on a hard drive. Because everything processes locally in the browser via the Web Audio API, your audio file is never uploaded anywhere.
Any browser released in the last few years supports this — Chrome, Edge, Firefox, or Safari all work. You don't need an account, a plugin, or a specific operating system; just an internet connection to load the page once, after which the audio processing itself needs no connection at all.