Why you end up needing a different audio format
Formats rarely matter until something refuses a file. Typical situations:
- A voice memo from an iPhone arrives as M4A, and an old car stereo, a website form or a podcast host wants MP3.
- A WhatsApp or Telegram voice note is OGG or OPUS, and you need it in a format a video editor or transcription service accepts.
- A DAW or audio editor wants WAV for editing, but you have MP3 or FLAC.
- A CD archived as WAV needs FLAC to save space, or MP3 copies for a phone.
This converter reads MP3, WAV, OGG, M4A, FLAC, AAC, OPUS and WMA, and writes MP3, WAV, OGG, M4A or FLAC.
Lossy and lossless: the one distinction that matters
Every audio format falls into one of two groups, and the group decides what conversion can and cannot do.
Lossless formats keep every sample of the original. WAV stores raw PCM samples; FLAC packs the same samples with compression similar to a ZIP file, typically ending up at 50 to 70% of the WAV size. Converting WAV to FLAC and back yields identical audio.
Lossy formats (MP3, AAC in M4A, Vorbis in OGG, Opus, WMA) throw away parts of the sound that a psychoacoustic model judges inaudible. The discarded detail is gone for good.
Practical rules that follow:
- Lossless to lossy is the normal direction, such as WAV to MP3.
- Lossy to lossless (MP3 to WAV or FLAC) does not restore anything. It is only useful when a program insists on WAV.
- Lossy to lossy (M4A to MP3, OGG to MP3) adds a second generation of compression. At 192 kbps one extra step is very hard to hear, but avoid chaining conversions repeatedly.
What each output setting means
The settings are fixed per format and chosen for a good balance of quality and size:
- MP3 uses the LAME encoder at a constant 192 kbps. That is about 1.4 MB per minute of stereo, or roughly 5.5 MB for a four-minute song. It plays practically everywhere.
- M4A contains AAC at 192 kbps, which sounds slightly better than MP3 at the same bitrate and is native to Apple devices.
- OGG contains Vorbis at quality level 5, a variable bitrate that averages around 160 kbps. It is open and royalty-free, but less supported by car stereos.
- WAV is uncompressed 16-bit PCM, the same bit depth as an audio CD. CD-quality stereo takes about 10 MB per minute. Sources recorded at 24-bit are reduced to 16-bit, which is inaudible for listening but worth knowing if you plan further studio processing.
- FLAC is lossless compression of the same samples, so it sounds identical to WAV at a smaller size.
The sample rate and number of channels are kept from the source. A mono voice memo stays mono, and a 48 kHz recording stays 48 kHz.
How it runs, and the size limits
The conversion uses FFmpeg, the open-source media engine, compiled to WebAssembly so it runs inside your browser. The engine is about 30 MB and downloads once, then the browser caches it. After that, files are converted on your device without being uploaded. Several files can be converted at once and downloaded as a ZIP.
In-browser conversion handles files up to 256 MB each, which covers several hours of MP3 or around 25 minutes of uncompressed WAV. For larger files there is a server option on the page: one free run a day for files up to 500 MB, and with Premium, files up to 4 GB without the daily limit. The server uses the same FFmpeg settings, so the result is identical.
Troubleshooting and tips
- Album art disappears. Cover images are stored as a picture stream inside MP3 and M4A files, and the converter keeps only the audio. Re-add artwork in your music library app if you need it.
- The output is much bigger than the input. Expected when going from MP3 or M4A to WAV or FLAC; lossless files are several times larger. If you need a smaller MP3 rather than a different format, compress the MP3 at a lower bitrate.
- A file is rejected or fails to convert. Check that it is really audio: some
.m4aor.webmfiles from screen recorders also carry video. For video files, use MP4 to MP3 to pull out the soundtrack. - Only part of the recording is needed. Convert first, then trim the MP3 to the section you want, which keeps the upload or attachment small.
- The tab runs out of memory. Long WAV files on phones can exceed a tab's memory; use a desktop browser or the server option.