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Trim Audio

Cut a section out of a track and keep the format it came in. Runs entirely in your browser.

Why an instant cut cannot be an exact one

Compressed audio is not a continuous stream of samples. It is a sequence of frames, each holding a fraction of a second and each decoded with reference to what surrounds it. There is no way to begin playing in the middle of a frame without decoding it first.

That gives two honest options, and this page offers both rather than picking one and hiding it. Copying the frames is instant and perfectly lossless, but the cut has to land on a frame boundary — the nearest one to where you clicked, which can be a fraction of a second away. Decoding and re-encoding cuts exactly where you asked, and costs time plus one generation of compression.

Exact is the default, because for the things people trim audio for — a ringtone, a podcast clip, a sample — starting a beat late is more irritating than waiting a few seconds. Fast is there for when you are pulling a rough section out of a long recording and precision does not matter.

The format comes back as it went in

An MP3 gives an MP3, a FLAC gives a FLAC. When an exact cut needs to re-encode, the encoder is chosen to match the container: LAME for MP3, FLAC for FLAC, uncompressed PCM for WAV. Mismatching those is a classic way to produce a file that will not mux, or one whose extension quietly disagrees with its contents.

For WAV and FLAC there is no quality question at all — both are lossless, so an exact cut reproduces the same samples the original had. The trade only exists for the lossy formats.

Trim Audio FAQ

Is my audio uploaded?

No. The file is played back and cut entirely on your own device. Recordings are among the most personal files people handle — voice notes, interviews, therapy sessions, music you have not released — and none of it leaves the tab.

What is the difference between the Exact and Fast options?

Fast copies the audio data straight through without decoding it, which is instant and completely lossless — but a compressed audio file can only be cut at frame boundaries, so the cut lands on the nearest one, up to a fraction of a second from where you asked. Exact decodes and re-encodes, so it cuts at the sample you specified, at the cost of time and one generation of re-compression. Exact is the default because being off by a beat is usually more annoying than waiting.

Why can't a fast cut be exact?

Because compressed audio is stored in frames that depend on the data around them, so there is no way to start playback mid-frame without decoding. Copying the data means keeping whole frames, and whole frames means the nearest boundary. This is not a limitation of this tool — it is how MP3, AAC and Vorbis work. Any tool offering instant cuts is doing the same thing, whether or not it tells you.

Do I get the same format back?

Yes. An MP3 in gives an MP3 out, a FLAC gives a FLAC. When re-encoding for an exact cut, the encoder is matched to the container — MP3 with LAME, FLAC losslessly, WAV as uncompressed PCM — so you never end up with a file whose extension disagrees with its contents.

Does an exact cut on a WAV or FLAC lose quality?

No. Both are lossless formats, so re-encoding reproduces the same samples. The quality trade-off only exists for lossy formats like MP3, AAC and Vorbis, where a second encoding pass is a real, if usually inaudible, cost.

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