A spectrogram is a visual representation of the frequency spectrum of an audio signal as it varies over time. The horizontal axis represents time, the vertical axis represents frequency (in Hz), and the color intensity represents amplitude (loudness) in decibels (dB). This tool uses the Short-Time Fourier Transform (STFT) to compute the spectrogram — the audio is divided into overlapping windows, each window undergoes an FFT, and the resulting magnitude spectra are stacked to form the 2D image. Brighter/warmer colors indicate stronger frequency components at that time-frequency point.

Smaller FFT sizes (512–1024) provide better time resolution but coarser frequency resolution — ideal for spotting fast transients and percussive events.
Larger FFT sizes (4096–8192) provide finer frequency resolution but smear details in time — better for analyzing harmonic structures and steady-state tones.
The default of 2048 offers a balanced compromise for most audio material. At 44.1 kHz sampling rate, this gives approximately 21.5 Hz frequency resolution per bin.

Logarithmic scale (default) more closely matches human pitch perception — each octave spans the same vertical distance. This is ideal for music analysis, speech formants, and general audio inspection.
Linear scale shows all frequencies with equal spacing, which can be useful for scientific analysis or when examining high-frequency details. Switch between modes using the Scale selector to find what works best for your specific use case.

This tool leverages your browser's built-in audio decoder, supporting all formats your browser can handle. Commonly supported formats include: WAV (uncompressed), MP3, OGG/Vorbis, FLAC (lossless), AAC/M4A, and WebM audio. If a file fails to decode, try converting it to WAV or MP3 format first. All processing happens locally — your audio files never leave your device.

Darker colors (purples, deep blues) represent low amplitude / quiet sounds, while brighter colors (yellows, whites) indicate high amplitude / loud frequency components. The dynamic range is approximately 80 dB — the brightest pixels are near the peak level, and the darkest represent sounds 80 dB below peak. Different color maps (Inferno, Viridis, Plasma, Grayscale, Cool-Warm) offer alternative visual interpretations of the same data. Choose the one that best highlights the features you're interested in.

Yes! Click the download button () in the control bar to save the current spectrogram as a PNG image. The exported image includes the spectrogram with axis labels and the color legend. You can also interact with the spectrogram — click anywhere on it to jump playback to that point, and hover to see the exact time and frequency at your cursor position.

Absolutely. All audio processing is performed entirely within your browser using the Web Audio API. Your audio files are never uploaded to any server. The spectrogram computation, audio playback, and image export all happen locally on your device. This tool can function completely offline once the page is loaded — there is zero data transmission.

The spectrogram rendering adapts to your screen width while preserving the correct time-frequency relationship. On narrower mobile screens, the horizontal time axis is compressed, which may make short-duration events less visible. For detailed analysis, we recommend using a desktop or tablet with a wider display. All controls remain fully functional on mobile devices, and you can still tap the spectrogram to navigate, adjust FFT parameters, and switch color maps.