Trim audio

How Audio Trimmer works

The file is read with a FileReader, rewritten in memory and offered as a download. This is why large PDFs are limited by your device's RAM rather than by an upload size limit. A 200 MB scan never crosses the network, so the slowest part is your own disk.

That is the whole architecture: static files, one script, no upload endpoint to leak or log. Close the tab and the work is gone.

Why the waveform matters

Trimming by ear means hunting for a start point twice: once to find it, once to check it. A waveform turns that into a visual task — the silence before someone speaks is a flat line, a clap is a spike, and the chorus is visibly louder than the verse.

The two markers are sliders, so they work on a phone as well as with a mouse, and the region outside the selection is dimmed on the canvas.

What happens to the audio

The browser decodes the file to raw PCM samples — 44,100 of them per second per channel for a CD-quality file. Cutting is then a slice of that array, which is why the operation is instant and does not degrade the audio.

Export writes a standard 16-bit WAV: a 44-byte header followed by the samples. That is the only audio container a browser can produce without embedding an MP3 encoder.

Getting the file size back down

WAV is uncompressed: one minute of stereo CD audio is about 10 MB. If that is too heavy to send, run the result through the audio converter on this site to get an MP3 or M4A back.

Keeping the intermediate lossless is the right order: cut first, compress last, so the audio is only compressed once.

Good to know

• Works offline once loaded, including on flights and in locked-down networks.
• No file size limit beyond your device's own memory.
• Free to use, with no account and no usage counter.
• Results are produced locally, so they are not logged or shared with anyone.

Questions