Simple HTML5 realtime audio analysis for both time domain and frequency domain in a <canvas> element in the browser.
You may access the app in my personal website: https://grossato.com/html5-simple-audio-analysis/
There are no analytics, no tracking, no ads or anything else, it is as simple as I could make it.
This is just a simple implementation of the AudioContext API. It uses window.AudioContext's createAnalyser method to create an analyzer and then we use getByteFrequencyData or getByteTimeDomainData to read the sound input buffers into a UInt8Array which is then displayed in a newly created canvas element.
Yes, it is free and license-less.