Audio cutter and MP3 cutter, with fades and no upload

A copy cut or an encoded cut

Compressed audio is stored in short frames, and each frame can only be kept or left out as a whole. In our test files an MP3 frame lasted 26 milliseconds and an AAC frame 21 milliseconds. When you keep the original format and add no fades, the cutter copies the frames inside your part exactly as they are: no decoding, no encoding, no change in quality or bitrate.

When you add a fade or pick another format, the part has to be decoded and encoded again. This is what happens to each kind of file:

A copy cut keeps whole frames, so it begins on the first frame at or after your start and can sit a few hundredths of a second inside the times you set. In our test, a 10-second copy cut from a 192 kbps MP3 took 30 milliseconds, and all 382 frames in it were identical to the original's. When a cut has to land on the exact sample, add a fade or save as WAV: WAV and FLAC are always cut to the sample. Opus is the exception among copies: an Opus file can tell players how much sound to skip at its start and end, so its copy plays exactly the times you set.

Fade in and fade out

Cutting into the middle of a song can leave a click where the sound starts or stops at full volume. A fade lowers the volume to silence over the time you pick, from half a second to 5 seconds, along a smooth S-shaped curve that starts and ends gently. If the two fades together are longer than the part, both are shortened in proportion so they fit.

In our test, a 10-second MP3 with a 1-second fade in and a 2-second fade out began and ended in silence, played at the original level in between, and was ready in about a third of a second.

Cut a song for a ringtone on iPhone or Android

For an iPhone, use the iPhone ringtone maker instead: it keeps the part to the 30 seconds Apple allows and saves an M4R, or an M4A to finish in GarageBand.

For an Android phone, cut the part here and save it as MP3 or M4A, then set it with the Files by Google app. Google's steps: under Categories, open Audio, find and play the file, tap More, then Set as ringtone, and turn on Allow modify system settings when the app asks (Files by Google Help). To give one person their own ringtone on a Pixel, open Contacts, tap the contact, then More and Set ringtone (Pixel Phone Help).

A ringtone plays from its first moment, so start the part right on the beat or the first word, and a half-second fade out stops it ending with a click.

Cut one file into several parts

The file stays open after you download a part. Move the handles to the next part and press Cut the audio again: each part becomes a new file, and the file you opened is never changed. That is how to split a long recording into songs, or a lecture into topics.

Each cut keeps one stretch, from your start to your end. Joining parts into one file, or taking a piece out of the middle and keeping both sides, needs an audio editor.

Which format to save

Original format keeps what you opened, which is usually best. The other choices, per minute of stereo sound:

MDN describes AAC as giving more compression with higher fidelity than MP3 (MDN). A higher MP3 setting than the file you opened makes a bigger file, not a better sound.

Cut the sound out of a video

The cutter also opens MP4, MOV, WebM and MKV videos and keeps only their sound, which is handy for a clip of a speech or a song from a recording. A video with AAC sound gives an M4A copy of the part you choose. To keep the whole sound of a video as an MP3, use video to MP3.

Long recordings and large files

There is nothing to upload, so a two-hour concert recording or a big WAV opens as quickly as a short song, with no size cap set by a server. The file is read from your device in small pieces, and only the part you keep is held in memory until you download it: ten minutes of a 320 kbps MP3 is 24 MB, while ten minutes of 44.1 kHz stereo WAV is about 106 MB. On a phone, keep long WAV parts short, or save them as MP3.

What happens to your file

The file is read on your device and never uploaded. The first time you open a file, your browser downloads the cutter from uncrop.si, plus an encoder when your choice needs one. Under the download, a line counts every request this page has sent with data since you added your file.

The new file is written without tags: no title, artist, album, comment, cover art or recording date comes across from the original.

Which browsers can do it

A copy cut needs nothing special from the browser, because the page reads and writes the frames itself. Fades and other formats need sound decoding on the device (WebCodecs), which Chrome and Edge have from version 94, Firefox on computers from version 130, Samsung Internet from version 17 and Safari from version 26 (caniuse, WebKit). MP3 is encoded by LAME, AAC by the browser or by FFmpeg's AAC encoder where the browser has none (Mediabunny), and FLAC by libFLAC. If something will not work in your browser, the tool says so before it starts.