I needed a fast FFT library for audio analysis on the web and found PFFFT. PFFFT is a small, pretty fast FFT library programmed in C with a BSD-like license. I have taken it upon myself to compile a WebAssembly version of PFFFT to make it available for browsers and node.js environments. It is called pffft.wasm and available on GitHub: https://github.com/JorenSix/pffft.wasmThere is a SIMD and non-SIMD version. Their performance can be compared in the benchmark tool. Run it on your machine to see the difference and compare it with a pure Javascript FFT library.