PyFDA Web — Online Python Filter Design Analysis Tool
PyFDA Web is a free, open-source web application that brings the power of
Python filter design directly to your browser. It is the online version of
PyFDA (Python Filter Design Analysis),
requiring no installation, no server, and no account. All signal processing runs locally
in your browser via Pyodide (CPython compiled to WebAssembly), with
computations powered by SciPy and NumPy.
Design IIR and FIR Digital Filters Online
Choose from a comprehensive set of filter design methods including
Butterworth, Chebyshev I/II,
Elliptic (Cauer), and Bessel for IIR filters,
or Windowed (firwin), Equiripple (Remez),
Least-Squares (firls), and Moving Average for
FIR filters. Design lowpass, highpass, bandpass, bandstop, and allpass
responses with full control over passband ripple, stopband attenuation, and filter order.
Interactive Analysis & Visualization
Once your filter is designed, PyFDA Web provides interactive plots for:
- Magnitude response — |H(f)| in dB, linear, or power units
- Phase response — continuous and wrapped phase
- Group delay and phase delay
- Pole-zero plot — visualize filter stability on the z-plane
- Impulse response h[n] and step response
- Custom stimulus simulation — apply arbitrary input signals
- 3D surface |H(z)| — view the transfer function over the entire z-plane
Fixpoint Simulation
Simulate the effects of fixed-point quantization on your filter.
Configure integer and fractional bit widths for both coefficients and signals,
select overflow behavior (saturate or wrap) and quantization mode (round, truncate,
floor, ceil), and compare the quantized response against the ideal floating-point design.
Export Your Filters
Export designed filters in multiple formats for use in your own projects:
NumPy (.npz), CSV (.csv),
MATLAB (.mat), and JSON (.json).
Copy coefficients (b, a), second-order sections (SOS), or poles and zeros
directly to your clipboard.
Why Use PyFDA Online?
- 100% client-side — no data leaves your browser
- No installation required — works on any modern browser
- Powered by real Python (SciPy, NumPy) via Pyodide/WebAssembly
- Open source under GPLv3
- Dark and light theme support
- Mobile-friendly responsive interface
PyFDA Web is ideal for students, engineers, and researchers who
need a quick, accessible digital signal processing (DSP) tool for
python filter design without setting up a local Python environment.
This application requires JavaScript to run. Please enable JavaScript in your browser
to use PyFDA Web.