Remove a section or keep only one
The two cut buttons solve opposite jobs. Remove selection marks the highlighted interval as unwanted and keeps the rest of the file. Use it repeatedly to take several interruptions, pauses or false starts out of a longer recording. Keep only selection discards everything before and after the highlighted interval. It also replaces earlier cuts, so use it when the final result should be one continuous excerpt.
Touching or overlapping removed intervals are merged into one cut. The list below the waveform shows every resulting interval, its removed duration and an Undo button for that row. The exported segments are the complement of that list: they stay in their original order and are joined into one output timeline.
A cleanup pass that is easy to check
- Wait for Ready so the complete waveform and Convert state have finished scanning.
- Drag over the first unwanted section. Use Play to audition the highlighted range when native preview is available.
- Press Remove selection. Repeat for every separate section that should disappear.
- Play across each remaining boundary. Preview skips removed intervals, so what you hear follows the kept timeline rather than replaying a deleted section.
- Choose MP3, M4A or WAV and check the remaining duration shown beside Convert.
PrivateMP3 does not search for silence, speech or beats. A low waveform can be intentional quiet audio, so every cut remains a user decision.
Use the time fields for a close boundary
The Start and End fields accept plain seconds such as 90, minutes and seconds such as 1:30.5, or an hour form such as 1:02:03.250. A comma is also accepted as the decimal separator. Values are kept inside the file duration, and the start cannot pass the end.
Keyboard controls provide smaller adjustments without trying to drag a narrow handle on a phone or trackpad. Left and Right move the focused selection or boundary by 0.1 seconds. The I and O keys set the start or end at the current playhead. Delete or Backspace applies Remove selection. Ctrl or Command with Z restores the preceding edit; Ctrl+Y or Command+Shift+Z reapplies it.
Volume edits belong to a selected interval
Up and Down change the selected interval by 1 dB, within the editor's −24 dB to +12 dB range. The change remains attached to source time, so it stays aligned when an earlier section is removed. Preview applies those volume regions as playback crosses them.
A volume change is not metadata. It changes decoded sample values and therefore prevents the unchanged packet copy, just as a cut does. Changing to another audio track also clears selections, cuts, volume changes and undo history after a confirmation because those times belong to the old track.
Cut position and output quality are separate choices
The worker decodes the kept segments and trims them to audio sample-frame boundaries before assigning a continuous output timeline. It does not preserve compressed MP3 frame boundaries around a cut. The chosen output then determines what is encoded:
- MP3 makes a new 192 kbps MP3. Cutting an existing MP3 therefore adds another lossy encoding.
- M4A makes new 192 kbps AAC after any cut or volume change. Only a complete, unchanged AAC, AC-3 or E-AC-3 track can use packet copy.
- WAV writes decoded audio as 16-bit PCM. It avoids another lossy encoding but cannot restore detail already removed from a lossy source.
There is no bitrate selector on this page. Claims about 256 or 320 kbps, or that a new 192 kbps encode is always inaudible, would not describe this implementation.
Measured: cutting an MP3 makes a new, larger MP3
Tested on 6 October 2026 in Chrome 154.0.8037.98 and Edge 154.0.4258.53 on Windows 11 (Intel Core i5-13600KF, 32 GB), with files generated by FFmpeg from a 220 Hz tone and quiet pink noise. Times are from Chrome; Edge differed by at most 0.7 s on any row. Each saved file was read back with ffprobe. The method is described in the screen recording test results.
The source was a five-minute MP3 at 128 kbps, 44.1 kHz stereo, 4,801,140 bytes. File check listed it as MP3, 128 kbps. Exported unchanged in length:
| Output | Time | Saved size | What happened |
|---|---|---|---|
| MP3 | 2.7 s | 7,201,801 bytes | Decoded and encoded again at 192 kbps |
| M4A | 1.7 s | 7,255,842 bytes | New AAC at 192 kbps |
| WAV | 2.4 s | 52,927,532 bytes | 16-bit PCM, 44.1 kHz stereo |
The new MP3 is 50 percent larger than the 128 kbps original and cannot sound better than it; there is no packet-level MP3 cut here. When the source is already a small MP3 and the only job is trimming silence, expect the file to grow. The output also ran 94 ms longer than five minutes, which is encoder padding at the ends.
Long files still need a complete scan
The waveform is built progressively from decoded samples instead of waiting to display one final image, but the complete track still has to be read before Ready appears. A three-hour recording is not expected to open as quickly as a three-minute one. Conversion also processes every kept segment before the output can be finalized.
The work stays on the device, but browser memory, storage and background-tab behavior still matter for long edits. Keep the tab and screen active during conversion. If the scan stops, the waveform diagnostic guide separates decoder, duration and damaged-container failures.