Audio Spectrum Analyzer — Free Online FFT Viewer
This audio spectrum analyzer online free draws the real-time frequency spectrum of any sound straight in your browser. Use your microphone or drop in an audio file (MP3, WAV, M4A, OGG, or FLAC) and watch a live FFT graph from 20 Hz to 20 kHz. It labels the loudest peaks with their exact Hz and nearest musical note. There is no download, no account, and nothing uploaded — it runs entirely on your device, on phone, tablet, or computer.
Tap Use microphone or drop an audio file to start the spectrum. Read left to right as pitch and up and down as loudness; the three loudest peaks are labelled with their frequency and nearest note. Tap Settings to change FFT size, smoothing, or the dB range, and Pause to hold the graph still.
Ready to see your sound's frequencies? Open the analyzer and choose your microphone or a file.
Use the free Audio Spectrum Analyzer →How to Use the Audio Spectrum Analyzer
Because this real time spectrum analyzer online works in any modern browser, there is nothing to install. The flow is just three steps:
- Open the tool — go to capsuletools.app/audio-spectrum-analyzer/ and choose an input.
- Choose an input — tap Use microphone, or drop in an audio file.
- Pick microphone or file — tap Use microphone and allow access, or drop an audio file onto the box.
- Read the spectrum — the frequency graph updates in real time. The top three peaks are labelled with their Hz and note; open Settings to fine-tune the view.
Like any fft spectrum analyzer online, it shows exactly which frequencies a sound contains, in real time — no cables, no extra software, no sign-up.
Microphone Input — Real-Time Spectrum from Your Device
Tap Use microphone and allow access when your browser asks, and your device becomes the input. Whistle, sing, play an instrument, or hold the phone near a speaker and the live spectrum reacts instantly. This is a free online audio spectrum analyzer via microphone — effectively an online spectrum analyzer mic that uses your built-in microphone as the probe. Nothing is recorded or uploaded; the audio is read only to draw the graph.
Audio File Input — Analyze MP3, WAV, FLAC, and More
Prefer to inspect a recording? Drop an audio file onto the box to use it as an audio file spectrum analyzer online. The file is decoded and played back in your browser while the spectrum is drawn, so you both hear and see it. Supported formats include MP3, WAV, M4A, AAC, OGG, and FLAC — whatever your browser can play. The file never leaves your device.
Reading the Graph — Peak Frequencies and Musical Notes
The horizontal axis is pitch on a logarithmic scale, from deep bass at 20 Hz to bright treble at 20 kHz, with 100 Hz, 1k, and 10k marked. The vertical axis is loudness in decibels. A pure tone shows a sharp spike; noise and rich instruments show a broad, bumpy curve. The analyzer scans for the three loudest peaks and labels each with its exact frequency and the closest note — so a sound spectrum analyzer online free becomes a quick way to find a hum's pitch or the root note of a chord.
FFT Size, Smoothing, and dB Range — Advanced Settings
Tap the Settings gear to shape the analysis. FFT size (256 up to 32768) trades detail for speed — a larger size resolves closely spaced frequencies but costs more CPU. Smoothing averages each frame with the last for a steadier, less jumpy graph. The min and max dB range sets the top and bottom of the vertical scale, so you can zoom in on quiet detail or fit a loud signal. As an audio frequency analyzer online free, these controls let you match the display to whatever you are measuring.
Spectrum Analyzer vs Oscilloscope — What's the Difference
Both turn sound into a picture, but they show different things. An oscilloscope is a time-domain view — the raw waveform, loudness against time, so you see the shape of the wave. A spectrum analyzer is a frequency-domain view — loudness against pitch, so you see which frequencies the sound is made of. For finding a specific frequency or note, the spectrum is what you want; to study a wave's shape, try the free online oscilloscope instead. They are two views of the same signal.
Works on iPhone, Android, Mac, and PC — No Download
The spectrum analyzer is an installable web app, so it runs in Safari, Chrome, Firefox, and Edge on any device — a free audio spectrum analyzer iPhone and Android users can open without an app store. Add it to your home screen and it launches full-screen like a native app. Everything is processed on your device, so it works the same whether you are on a phone or a laptop.
Frequently Asked Questions
What is an audio spectrum analyzer?
An audio spectrum analyzer breaks a sound into its individual frequencies and shows how loud each one is, so instead of a single waveform you see a graph of level against pitch. This one runs a real-time FFT (Fast Fourier Transform) in your browser and plots frequency from 20 Hz to 20 kHz across the screen with loudness in decibels up the side. It is the frequency-domain view of sound, the tool you reach for to spot a hum, a resonance, or the root note of a tone.
How do you read an audio spectrum analyzer?
Read left to right as pitch — low bass on the left, high treble on the right — and up and down as loudness in decibels, with taller peaks meaning louder frequencies. A steady tone shows a sharp spike at its pitch; noise or a rich instrument shows a broad, bumpy curve. This analyzer labels the three loudest peaks with their exact Hz and nearest musical note, so you can name what you are looking at without doing the math.
How do you use an audio spectrum analyzer?
Choose a source, then read the graph. Tap Use microphone and allow access to analyze live sound, or drop in an audio file (MP3, WAV, M4A, OGG, FLAC) to analyze a recording. The spectrum updates in real time as the sound plays. Open Settings to change the FFT size for finer detail, adjust smoothing to steady the display, or set the dB range to zoom the vertical scale.
How does a spectrum analyzer work?
It repeatedly takes a short slice of the sound and runs a Fast Fourier Transform on it, a piece of math that converts the raw waveform into the mix of frequencies it contains. Each result is a set of frequency bins with a loudness value, which is drawn as the spectrum curve. This tool uses the browser's built-in Web Audio API to do the FFT on your device, many times a second, so nothing is uploaded and the graph stays live.
What's the difference between a spectrum analyzer and an oscilloscope?
An oscilloscope shows a sound in the time domain — the raw waveform, loudness against time — so you see the shape of the wave. A spectrum analyzer shows the same sound in the frequency domain — loudness against pitch — so you see which frequencies it is made of. They are two views of one signal: use the oscilloscope to study a wave's shape and the spectrum analyzer to find its frequencies. Capsule Tools has a free online oscilloscope for the waveform view.
Can I use my microphone as an online spectrum analyzer?
Yes — that is the main mode. Tap Use microphone and allow access when the browser asks, and your device's microphone becomes the input for a free online audio spectrum analyzer via microphone. Whistle, sing, play an instrument, or hold the phone near a speaker and the frequency graph reacts instantly. Nothing is recorded or uploaded; the audio is read only to draw the spectrum on your own device.
Use the free Audio Spectrum Analyzer →
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