Split an audio file into chunks

Cut on the waveform, or let the tool place the cuts

Once your file is open you see its waveform. Click anywhere to move the playhead, press Add cut to split there, and drag a cut marker to move it. Every cut shows up as a numbered row in the table underneath, where you can also type exact times, play just that chunk, or download it on its own.

Three presets place cuts for you. Equal parts divides the file into as many pieces as you ask for. Every splits at a fixed interval, five minutes for example, with a shorter last piece. Silence looks for quiet gaps of at least a given length and cuts in the middle of each one, which is how you turn a recorded album side, a lecture, or an audiobook file into tracks or chapters. After a preset you can still drag any marker.

Nothing is re-encoded

The tool does not decode your audio and encode it again. It copies the original compressed frames into each new file, so an MP3 chunk has exactly the sound quality of the MP3 you started with and takes seconds to make, not minutes. It also means the chunks keep the same format as the source: MP3 in, MP3 out.

Copying frames sets how precise a cut can be. MP3 frames are about 26 milliseconds long, AAC about 21, Opus 20, Vorbis up to 46 and FLAC blocks up to about 105, so a chunk begins at the nearest frame boundary. MP3 chunks after the first start a fraction of a second early (about 0.1 to 0.2 s at common bitrates, more at very low ones), and M4A chunks up to about 0.04 s early, so that nothing at the boundary is lost; the extra is what the decoder needs to get the first frame right. WAV is cut at individual sample frames.

Title, artist, album and cover art carry over to every chunk. Each one gets the title with "(part 3)" added and a track number, so an audiobook split into chapters sorts correctly in any player.

Your file stays on your device

The splitting runs inside your browser using the open-source mediabunny media engine. Your browser reads the file from disk, cuts it in the tab, and hands the pieces back as downloads. It is not uploaded to NoAdsTools or anywhere else.

You can check this in your browser's Network panel. The first time you add a file, the page downloads the 660 KB engine from this site. If you press Download all, it also fetches a 97 KB ZIP packer, once. Your audio never goes out.

After the engine has arrived you can disconnect from the internet and keep splitting. Download all needs the ZIP packer to have arrived too; single-chunk downloads never do.

The full source is public on GitHub under the AGPL-3.0 license, and the privacy page lists exactly what this tool loads and when.

Questions

Can I split an MP3 online without uploading it?

Yes. The file is read and cut inside your browser. Your audio is never sent to a server, which you can verify in the Network panel while you work.

Do I need an account to download the chunks?

No. There is no account, no email, no daily limit, and the download button is a download button.

Does splitting an MP3 lose quality?

No. The frames are copied, not re-encoded, so a chunk has exactly the sound quality of the file it came from. The one thing copying cannot do is cut inside a frame, so a chunk begins at the nearest frame boundary, up to about 13 milliseconds either side of your cut for MP3. MP3 chunks after the first also start a fraction of a second early (about 0.1 to 0.2 s at common bitrates), and M4A chunks up to about 0.04 s early, so nothing at the boundary is lost.

Why is my cut a few milliseconds away from where I put it?

Compressed audio comes in frames, and the tool cuts on the nearest frame boundary to avoid re-encoding. MP3 frames are about 26 ms, AAC 21 ms, Opus 20 ms, Vorbis up to 46 ms and FLAC blocks up to about 105 ms, so a cut can move by up to half a frame. WAV is cut at individual sample frames.

How do I split an audiobook into chapters?

Open the file, choose Silence, and set how long a pause has to be to count as a chapter break. Two seconds catches most narrated books. Check the result on the waveform, drag any marker that landed wrong, then Download all. Each chunk is tagged with a part number so it plays in order.

How large a file can it handle?

The tool reads the file from disk in pieces rather than loading it whole, so length is not the limit. Each chunk and the ZIP are built in your browser's memory, so very large chunks, and a ZIP of a very large file, need enough free memory; past a few hundred megabytes that can fail on phones and in some browsers. If Download all fails, download the chunks one at a time.

Related tools

Compress Video | shrink a video to a target size the same no-upload way. Split PDF | pull pages out of a PDF in the browser.