Free Online Spectrogram
See every frequency across time.
Drag & drop your audio file here
or
Max file size: 100 MB · MP3, WAV, FLAC, OGG
Original
beats per minute
musical key
Brighter colors mean more energy at that frequency and moment.
Processing…
Result
How it works
A spectrogram reveals what a waveform hides: how the frequency content of sound changes over time. It slices your audio into tiny overlapping windows, runs a Fast Fourier Transform on each to measure the energy at every frequency, and paints the result as an image - time on the horizontal axis, frequency on the vertical, brightness as energy.
Choose from four scientific colormaps - inferno, viridis, grayscale and plasma - and export a 1200x600 PNG. What you will see: the harmonic ladder of musical notes, the pitch wobble of a voice, the snap of transients, even compression artifacts invisible to the ear.
All analysis is client-side: the FFT runs in your browser tab and the image is rendered on a local canvas, so your audio never leaves your device and nothing is uploaded to any server.
Frequently asked questions
How do I read a spectrogram?
Time runs left to right, frequency runs bottom (bass) to top (treble), and brightness shows energy. Horizontal lines are steady tones (like a humming fridge or a sung note); vertical bursts are transients (drum hits, consonants). The bright curve wiggling through a vocal recording is the pitch contour.
What are spectrograms used for?
Audio forensics, finding hidden messages in tracks, analyzing bird calls and whale song, checking for clipping and compression artifacts, and making beautiful science-art prints.
Which colormap should I pick?
Inferno and plasma show fine detail best for analysis; viridis is colorblind-friendly; grayscale is best for print. They all show the same data.
Is there a file size limit? Is it private?
Files up to 100MB are supported. The FFT analysis and PNG rendering happen entirely in your browser - your audio never leaves your device.