Free Online Fourier & DSP Tools
Compute FFTs, generate signals, design filters, and explore spectrograms — all in your browser. No installation, no data uploads, no cost.
All Tools
Click any card to launch the tool instantly. Every tool works on desktop and mobile.
FFT Calculator
Paste or generate a signal, compute its FFT, and explore the magnitude and phase spectrum interactively.
Signal Generator
Build complex signals by mixing sine, square, sawtooth, and triangle waves with adjustable frequency, amplitude, and phase.
Spectrogram
Visualize how the frequency content of a signal changes over time with a live, color-mapped spectrogram.
Filter Designer
Design lowpass, highpass, bandpass, and notch filters. See the frequency response and apply to live signals.
Convolution Demo
Visualize convolution step by step — see how two signals combine to produce a third with animated overlap.
NewCSV to Spectrum
Upload a CSV of time-series data and instantly see its frequency spectrum. Export the result as PNG or CSV.
Popular Tasks
Jump straight to step-by-step walkthroughs for common signal processing tasks.
How It Works
Choose a Tool
Pick the FFT Calculator, Signal Generator, Spectrogram, or any of our six tools above.
Configure & Compute
Adjust parameters with intuitive sliders and dropdowns. Results update in real time.
Explore & Export
Hover for exact values, zoom in on peaks, and export your results as PNG or CSV.
Frequently Asked Questions
Are these tools really free?
Yes — every tool on Fourier Tools is 100% free, runs entirely in your browser, and requires no sign-up or installation.
Do my signals or data leave my computer?
No. All computation happens client-side in your browser using JavaScript and the Web Audio API. Nothing is uploaded to a server.
Can I use these tools on mobile?
Most tools work on modern mobile browsers. For the best experience with sliders and large spectrograms, a desktop or tablet is recommended.
What sample rates and sizes are supported?
The FFT Calculator supports sample sizes from 64 to 4096 points. The Signal Generator and Spectrogram use the Web Audio API default of 44,100 Hz, but you can adjust effective rates in the FFT tool.
How accurate are the results?
The tools use standard algorithms (Cooley–Tukey radix-2 FFT, IIR/FIR filter designs). Results match MATLAB/SciPy to floating-point precision for the same inputs.
Start with the FFT Calculator
Generate a signal, compute its FFT, and see the frequency spectrum in seconds.
Launch FFT Calculator →