Trimming
Drop in a file and its waveform is drawn. Drag the two handles at the ends to choose the part to keep, or type exact times into Start and End as seconds (12.5) or minutes and seconds (1:02.25). Click the waveform to put the playhead there. Focused handles move with the arrow keys, a hundredth of a second at a time, or a tenth with Shift. Trim silence at the ends moves the handles in past any near-silence at the start and end of the selection.
Hearing it first
Play selection plays the part you chose with every change applied: fades, volume, speed, reverse and mono. It is built from the same steps as the saved file, so what you hear is what you get. Play all plays the whole original from the playhead. Space plays and stops.
Volume and normalize
The volume slider runs from −30 to +30 dB; +6 dB is about twice the level, −6 dB about half. Normalize sets it so the loudest moment of the selection lands at −1 dB below full scale, as loud as it can go with a little room to spare. Raising it past that clips the peaks, and the page warns you when it would.
Saving
MP3 plays everywhere; 192 kbps is hard to tell from the original, 128 kbps is smaller, 320 kbps is the most MP3 allows. WAV and AIFF are uncompressed 16-bit, exact but about ten times bigger. Opus is smaller than MP3 for the same quality, but older Apple devices may not play it. The file keeps the original's sample rate (MP3 is moved to 44.1 or 48 kHz if it was something else). Everything runs on your device, with the browser's own decoders and the LAME MP3 encoder.
Questions
Is my audio uploaded?
No. It is decoded, edited and saved in this page, on your device. Nothing is sent anywhere, so it is safe for voice notes, interviews and unreleased music.
Which files can I open?
Anything your browser can play: MP3, WAV, M4A and AAC, OGG, Opus, FLAC and AIFF, plus the sound of an MP4, MOV or WebM video. Safari cannot read OGG files, and some browsers cannot read the sound in every video; the page says so if yours cannot.
Is there a size limit?
No set limit, but the whole recording is held in memory, uncompressed, while you work: about 20 MB a minute for stereo. An hour-long podcast needs over a gigabyte, which a laptop handles and an older phone may not. For a long file, trim it first and save, then make the other changes.
Can I change the speed without changing the pitch?
Not here. Speed works like a turntable: faster is higher, slower is lower. Doing one without the other needs a time-stretching algorithm that browsers do not include, and a rough one would sound worse than an honest turntable.
Can I turn the result into another format?
Yes. The File Converter turns audio into MP3, WAV, AIFF, Opus and AAC, and pulls the sound out of videos.