A WebAssembly implementation of the C Fast Fourier Transform library kissFFT
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thejozhou Merge pull request #15 from AWSM-WASM/fix-toolchain
updates based on latest emscripten change logs, fix compiling error
Latest commit 72e281e Aug 29, 2018


Pulse FFT

A WebAssembly implementation of kissFFT, the 'keep-it-simple-stupid' Fast Fourier Transform library written in C. This project allows forward and inverse FFTs to be computed with low-level processes in the browser with the performant WebAssembly format.

Sample app

Watch Pulse convert real-time microphone input from the time/space domain to the frequency domain.

Frequency Spectrum

Get Started

Download Emscripten

$ git clone https://github.com/juj/emsdk.git
$ cd emsdk
$ ./emsdk install --build=Release sdk-incoming-64bit binaryen-master-64bit
$ ./emsdk activate --build=Release sdk-incoming-64bit binaryen-master-64bit


This library is a WebAssembly implementation of kissFFT; consult the kissFFT README if you want more info on the internal FFT details.

Instantiate Pulse

let pulse = {};
    .then(module => {
        pulse = module;

Real Input

// Create the WebAssembly instance.
const fft = new pulse.fftReal(size);

Complex Input

// Create the WebAssembly instance.
const fft = new pulse.fftComplex(size);

Performance tests

For the benchmark test, 4000 iterations were performed on sample data of several different sizes (4, 8, 512, 2048, and 4096) on both .asm and .wasm formats. Both single-precision real and complex to complex FFT forwards were performed. The times for the first and second half of each test are shown separately to elucidate any differences caused by the Javascript engine warming up. The last column shows the rate at which each algorithm performed the 4000 iterations. For the larger buffer sizes, the Web Assembly compiled functions are consistently faster than their assembly compiled counterparts.


Make sure to clone the repo recursively, in order to get KissFFT.

git clone --recursive https://github.com/AWSM-WASM/PulseFFT.git

When finished, run npm start. This wil run the emsdk environment, compile the source code, and start the server at //localhost.8000.

Demo page coming soon!


KissFFT is not bundled in the source of this repository.


Jo Zhou
Augusto Alvarez
Chris Kim


Please submit issues/pull requests if you have feedback or message the PulseFFT team to be added as a contributor: PulseFFT@gmail.com


Here's our top development priorities

  • Caching .wasm client-side
  • Enabling >ES6 module loading
  • Refactoring to use async/await
  • Adding robust Mocha/Chai/Sinon testing
  • Logging / Debugging mode for development, feedback, and error reporting
  • Performance and stability updates
  • Improved documentation
  • Bundle and create npm package


PulseFFT is licensed under the MIT License.
KissFFT is licensed under the Revised BSD License.