What does MP3 Cutter do?
Cut MP3 files in your browser: drag handles on the waveform or type times, preview the selection, add fades and save a new MP3. Fast lossless mode.
- Price
- Free
- Account
- Not required
- Processing
- Entirely in your browser; your data and files are not uploaded
- Works on
- Any modern browser on desktop, tablet or phone
- Category
- Video and Audio Tools
How to use the mp3 cutter
- Drop an MP3 (other audio formats up to 100 MB also work and are saved as MP3).
- Drag the start and end handles on the waveform, or type exact times.
- Click Play selection to check it. Add a fade in or fade out if you like.
- Choose Fast (copy) for a lossless cut or Exact (re-encode) for sample-accurate edges, then click Cut and download.
Worked example
A 30 second ringtone from 1:15
Set the start to 1:15 and the end to 1:45. Fast mode copies those 30 seconds of MP3 frames without re-encoding, so a 192 kbps song gives about 192,000 x 30 / 8 = 720,000 bytes (about 703 KB). Adding a 2 second fade out switches to re-encoding because the samples change.
How it works
The waveform is drawn in the browser: the file is decoded with the Web Audio API at 8 kHz and the minimum and maximum sample of each slice are plotted. Cutting uses FFmpeg: -ss start -i input -t length -c:a copy for fast mode, which copies whole MP3 frames (1,152 samples, about 26 ms at 44.1 kHz). Exact mode re-encodes with libmp3lame and applies afade filters for fades.
Assumptions
- Fast mode cut points snap to MP3 frame boundaries, so they may be up to one frame (about 26 ms) off.
- Exact mode re-encodes the selection once, which is lossy for MP3.
- Non-MP3 inputs are always re-encoded to MP3.
Frequently asked questions
Are my files uploaded?
No. The file is processed by FFmpeg compiled to WebAssembly, running inside your browser. Only the engine itself is downloaded (once, from cdn.jsdelivr.net); your video, audio or images never leave your device.
What is the difference between Fast and Exact?
Fast copies the existing compressed MP3 frames between your start and end, so there is no quality loss and it finishes almost instantly, but the cut snaps to the nearest frame. Exact decodes and re-encodes the selection so it starts and ends precisely where you set it, and is required for fades.
Can I make a ringtone?
Yes. Select up to 30 or 40 seconds, add a short fade out, and download the MP3. iPhones need M4R files, which this tool does not create; use the Audio Cutter with M4A output and rename the file to .m4r.
Why does the first run take longer?
The first time you use any of the video and audio tools, your browser downloads the FFmpeg engine, about 31 MB. It is stored in your browser, so later runs on this device start without downloading it again unless you clear site data.
Limitations
- FFmpeg runs as single-threaded WebAssembly in the browser, which is much slower than desktop FFmpeg. Processing time depends on the file length, resolution and your device; long HD videos can take many minutes.
- Files up to 100 MB are accepted.
- Very long files may be too large for the browser to draw a waveform; you can still type times and cut.
- One selection per run. To remove a middle part, cut twice and join the pieces in an editor.