Question 1

Does cutting an MP3 lose quality?

Accepted Answer

Not here, and the reason is in how an MP3 is built. The file is a run of small independent frames, each carrying about 26 milliseconds of sound and each decodable on its own. Cutting one down means finding the frames inside your selection and copying them into a new file with a fresh header on the front. The audio bytes that come out are the audio bytes that went in, so the result is identical to that stretch of the original. What costs quality is the other way of doing it: decoding the whole file back to samples and compressing it again, which puts a second round of loss on audio that was already compressed once. Nothing on the default setting here decodes anything.

Question 2

How do I trim an MP3 down to just the part I want?

Accepted Answer

Drop the file in and it appears with a waveform and a selection already across it. To trim MP3 files down to a single stretch, drag the start handle to where the useful part begins and the end handle to where it stops, or type both times into the boxes underneath if you already have them off a transcript. Press play on the selection to check you got it, then press cut and download. The audio trimmer works the same on a two-hour lecture as on a three-minute song, because the file is read in slices off your disk rather than loaded whole. If you would rather find the spot by ear, click anywhere on the waveform to move the playhead there.

Question 3

Can I cut the middle out instead of the ends?

Accepted Answer

Yes, and it is one setting rather than two passes. Under How the cut runs, change The selection is to the part you want gone. Now the handles mark what disappears, and everything outside them is written into one continuous file with the two halves joined at the cut. That is the right shape for ninety seconds of dead air at the front of a recording, a false start, a phone ringing in the middle of an interview, or the adverts in a radio show you saved. Add more than one selection and all of them are dropped in the same pass. On the precise setting the join lands on a zero crossing, so there is no click where the middle used to be.

Question 4

How do I split one MP3 into several files?

Accepted Answer

To split MP3 files into separate tracks, add a selection for each piece you want. Press Add another piece under the waveform, set its start and end, and repeat: every selection comes out as its own file, numbered in order, with a ZIP button for the set. That is the job when a side of a vinyl or tape rip arrived as one long recording and has to become one file per track, or when a two-hour conference recording holds four talks. If the pieces have silence between them, Find the gaps works them out for you. As an mp3 splitter this never re-encodes, so twelve tracks out of one file cost twelve copies rather than twelve compressions.

Question 5

Can it find the gaps and split a long recording automatically?

Accepted Answer

Press Find the gaps on the file's row. It reads the whole recording, marks every stretch quieter than the threshold and longer than the minimum gap, and proposes one piece for each run of actual sound in between. Nothing is applied at that point: you see how many pieces it found and either take them or leave the file as it was. Take them and every boundary becomes an ordinary handle you can drag or retype before you cut anything. Two settings steer it. Take the threshold lower when a hissy recording comes back as one long piece, and raise the minimum gap when a speaker's pauses are being read as track breaks. To remove silence rather than split on it, set the selection to the part you want gone first: the gaps themselves are then what gets proposed, and cutting drops every one of them.

Question 6

Why is the cut a few milliseconds off where I put it?

Accepted Answer

Because a compressed file is not a continuous stream of samples, it is a run of frames, and a copy cannot begin halfway inside one. An MPEG-1 Layer III frame at 44.1 kHz holds 1152 samples, which is about 26 milliseconds, so the start of the cut moves to the nearest frame boundary. AAC in an M4A holds 1024 samples per frame, roughly 23 milliseconds. The exact figure for the file in front of you sits on its row before you cut, measured off that file rather than assumed from its format. WAV has no such limit, because its samples are stored raw, so a WAV cut lands exactly where you put it. When a boundary genuinely has to be sample-exact, the precise setting does that and re-encodes to get there.

Question 7

Can I cut a WAV, M4A or FLAC too?

Accepted Answer

Yes, and each one comes back as what it was. The wav cutter is the cleanest case: WAV holds raw samples, so the piece you keep is copied out sample for sample and the boundary lands exactly where you set it. M4A and AAC are copied frame by frame into a fresh MP4, which is also how you trim m4a voice memos without touching the audio inside them. FLAC and Ogg, both Vorbis and Opus, work the same way. There is no output format to pick here on purpose: a cut removes time, it does not change the format, so the file you get back opens in whatever opened the original.

Question 8

How do I make a ringtone out of a song?

Accepted Answer

Pick the thirty seconds you want, switch on Write it as an iPhone ringtone, and download the .m4r. A second or two of fade out at the end is worth having, because a ringtone that stops mid-note sounds broken. The part a website can finish ends there, and it is worth saying plainly: iOS will not install a ringtone straight from a download. On a Mac, drag the .m4r onto your connected iPhone in the Finder, then choose it under Settings, Sounds and Haptics. On Windows, iTunes does the same job. Android is easier: put the file in the Ringtones folder on the phone's storage and it appears in the sound picker.

Question 9

Can I fade the start and the end?

Accepted Answer

Yes, in seconds, in the settings under the tool. What it costs is worth knowing before you use it, which is why the tool says so where the control is rather than in a paragraph elsewhere. A fade changes the level of the samples themselves, and samples inside a compressed file cannot be changed without decoding them and compressing them again. So switching on a fade in or a fade out moves the cut to the precise mode, and the file goes through one round of re-encoding at the bitrate it already had. On a WAV, or on the tail of a ringtone, that costs nothing you can hear. On a copy you mean to keep as a master, leave the fades off.

Question 10

Can I cut the same bit off a whole folder of recordings?

Accepted Answer

Yes, and it is why the folder button is there. Press Choose a folder and pick the folder itself rather than the files inside it. Everything in it that holds audio joins the list, and the artwork and text files stay where they are. Set the selection once and every file follows it, so taking the same forty seconds of preamble off a term of lecture recordings is one action rather than forty. Any file that needs something different gets a selection of its own on its own row, with a button to put it back on the shared one. Several cut at once across the cores your machine can spare, and the whole set comes away as a single ZIP.

Question 11

Is there a limit on file size or length?

Accepted Answer

No. Nothing caps how large a file is, how long it runs or how many are in the list, and there is no allowance to use up. The file is read in slices off your disk rather than loaded into memory whole, which is what makes that a true statement rather than a hopeful one: taking thirty seconds out of a two-hour recording reads the few hundred kilobytes around the cut and copies them, so it finishes about as fast as your disk delivers them. Drawing the waveform is the slower half, and it fills in as it goes rather than making you wait for it. Nothing you ask for is queued behind anybody else.

Question 12

Do my files get uploaded anywhere?

Accepted Answer

No, and there is no server here that could receive one. Your file is read, cut and written back out by your own browser on your own machine. If you would rather check than take that on trust, open the network tab and cut something: nothing goes out. It matters more here than it might look, because of what a cutter gets used on. Someone trimming a two-hour meeting down to the eight minutes that matter has, by definition, something in the other hundred and twelve. A therapy session, a client call, a disciplinary hearing, a mix nobody else is meant to hear yet. Clear the list afterwards and nothing is left behind.

MP3 Cutter

Drop in an MP3, WAV, M4A, FLAC or Ogg file

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