The things people most often need to do to a sound file: cut it shorter, split a long recording into parts or join chapters into one, make a quiet voice memo louder, change its speed, shrink an MP3 under a limit, or turn it into the format a phone, an editor or an upload form will take. These tools do that in your browser, and each one prints the numbers that show it did the job properly — peaks against full scale, the real length the file reports, the bitrate it was written at.
Which one to use
| You want to… | Tool |
|---|---|
| Cut the start or end off a song, voice memo or recording | Trim Audio |
| Split a podcast, audiobook or long recording into parts at the pauses, or every N minutes, without re-encoding | Split Audio |
| Join MP3 chapters or parts into one file that shows its real length, without re-encoding | Merge MP3 |
| Shorten the long pauses and dead air in a podcast, lecture or voice memo without cutting quiet words | Remove Silence from Audio |
| Make a quiet recording, voice memo or podcast louder without distortion, or an MP3 louder without re-encoding | Increase Audio Volume |
| Speed up a lecture or slow down a song without changing the pitch, shift the key, or fit a recording to an exact length | Change Audio Speed |
| Play a song, a sound or your own voice backwards, for the reverse singing challenge or sound effects | Reverse Audio |
| Make an MP3 smaller, or fit it under a size limit; shrink an oversized cover picture without touching the sound | Compress MP3 |
| Record your voice, or singing without the call-style processing that fades held notes, as MP3 or WAV | Voice Recorder |
| Turn an M4A or a voice memo into an MP3, tags and cover art included | M4A to MP3 |
| Shrink a WAV recording to MP3 without clipping its peaks | WAV to MP3 |
| Make 320 kbps MP3s of a FLAC album, tags and cover art kept, checked for clipping | FLAC to MP3 |
| Turn a WhatsApp or Telegram voice note, or any OGG, into an MP3 | OGG to MP3 |
| Turn an MP3 into a 16-bit or 24-bit WAV for a CD, DJ software or a video editor | MP3 to WAV |
| Turn an M4A or a voice memo into a WAV; Lossless memos come out sample for sample | M4A to WAV |
| Make an iPhone ringtone from a song: pick the chorus, fade it, under 30 seconds for iOS 26 | MP3 to M4R |
| Save a video's sound as an MP3, at a bitrate that matches it | MP4 to MP3 |
| Get the sound of a screen or browser recording as an MP3 that shows its length | WebM to MP3 |
| Keep a video's soundtrack exactly as it is, or as WAV to edit or transcribe | Extract Audio from Video |
Working with the video itself — putting music on a clip, or turning a song and a cover picture into an MP4 for YouTube — is in the video tools: Add Music to Video and MP3 to MP4.
Copied where possible, converted only when needed
An MP3 or an AAC stream is already a finished, lossy file. A converter that decodes it and compresses it again has no idea what the first pass threw away, so it throws away more. That is why trimming, splitting and joining MP3s here can work on whole frames without re-encoding, and why Extract Audio lifts the sound out of a video with only the seven-byte header each frame needs to stand alone. The page prints the audio bytes, the framing bytes and the frame count, so the claim is arithmetic rather than a promise.
When the destination will only take MP3, M4A to MP3 does the conversion with a bitrate matched to the original, keeps the tags, and marks the encoder's 25 ms lead-in so the MP3 starts on the same sample as the source. MP4 to MP3 does the same straight from a video, reading only the sound track (a 60-second, 60.8 MB phone video took one second), and WAV to MP3 checks each recording first: peaks above full scale in 32-bit float files are lowered instead of clipped, and a voice recorded on one side only becomes mono at its full level rather than 6.5 dB quieter.
Length, loudness and the numbers behind them
Two things go wrong quietly with audio files. The first is length: an MP3 joined by gluing files together, or a recording made in the browser, often has no correct duration in it, so players show the wrong time and seeking jumps. Merge MP3 and WebM to MP3 write the real length into the file. The second is loudness: making a recording louder by multiplying the samples clips the peaks, and the distortion is permanent. Increase Audio Volume measures the result again and tells you the loudness, the loudest peak and how many samples reach full scale.
Nothing is uploaded — the sound is read on your machine and never sent anywhere. That is common in this category now rather than unusual, so it is not the reason to use these tools. The reason is that every claim on these pages comes with the number that backs it.