Audio trimmer — cut MP3, WAV and M4A files in your browser

How to use the audio trimmer

1. Drop an audio file onto the box, or click to choose one. The waveform appears once the file is decoded.
2. Drag the start and end handles to the part you want, or type exact times into Start and End (seconds; End 0 means “to the end”).
3. Press Play selection to check the cut.
4. Choose Save as: WAV (16-bit, lossless), M4A (AAC), WebM (Opus), OGG (Opus) or MP3. For compressed formats, pick a Bitrate.
5. Leave Anti-click fade at 10 ms unless you need a hard cut, then press Trim audio and download the file.

What it does and when to use it

The trimmer keeps one continuous section of a recording and throws away the rest. Typical jobs are cutting the silence and “is it recording?” mumble from the start of a voice memo, taking a clip from a podcast or interview, shortening a music track for a video, or preparing a sample for a presentation.

For a phone ringtone with the right length and format, the ringtone maker is quicker. If you need a different file type rather than a shorter file, use the audio converter. To smooth the beginning and end with longer fades, try audio fade in and out.

How it works

• The page draws the waveform by decoding the audio with the browser’s Web Audio API.
• When you press Trim, the file is processed in a Web Worker so the page stays responsive. WAV is read directly; other formats are opened with the open-source Mediabunny library (about 0.7 MB, loaded the first time) and decoded with WebCodecs.
• The kept samples are copied out, a linear fade is applied at each end, and the result is encoded: WAV by the site’s own code, AAC and Opus by your browser’s WebCodecs encoder, MP3 only through ffmpeg.wasm.
• The result reports the time range kept, such as 0:01.20 → 0:31.20, and its length.

Example

Suppose a 2-minute voice memo starts with 1.2 seconds of shuffling and you want the next 30 seconds. Set Start to 1.2 and End to 31.2, keep the 10 ms fade and save as WAV. You get a 30-second file with smooth edges. To drop just the opening silence from a memo, set Start to 0.5, leave End at 0, and save as M4A for a small file.

Limits and tips

• One section per file. To remove a piece from the middle, trim twice and join the parts with the audio merger.
• Long files use memory. The whole track is decoded to draw the waveform, so a very long, high-sample-rate recording can be slow on older phones.
• Older browsers without WebCodecs can still trim WAV files but cannot decode or encode compressed formats; use a current Chrome, Edge, Firefox or Safari.
• M4A plays almost everywhere, including iPhones. WebM and OGG with Opus are smaller for speech but are less common in older car stereos and players.