Audio Format Converter

The Audio Format Converter turns an audio file into MP3, WAV, M4A, or OGG. It is useful when a player, device, or program does not recognize the format you have. Those four are the only output formats, and there are no controls for bitrate, sample rate, channels, or quality; everything uses ffmpeg's default encoder settings. It does not promise to carry over tags such as title or cover art, and it handles one file at a time. If you need fine control over the output, a dedicated desktop program is a better fit.

How to use it

1. Click the dashed 'Click to upload audio' box and choose the file to convert. The box then shows its name.
2. Under 'Target format', click one of MP3, WAV, M4A, or OGG. The selected button turns dark. MP3 is the default.
3. Click 'Start Converting'. On the first use the button shows 'Loading processing core…' and then changes to 'Converting…'.
4. When it finishes, a player appears so you can listen, and then 'Download Converted File' saves it. The downloaded name is always converted. plus the chosen extension, such as converted.mp3, and the original file name is not kept.

Choosing a format, and a usage scenario

MP3 is the most widely compatible and plays on almost any player or device; it is lossy. M4A usually holds AAC audio, is also lossy, and is common on Apple devices and phones. OGG is an open format, again lossy, and some older devices do not support it. WAV is normally uncompressed, so it loses no further quality, but files are much larger. A typical scenario: you have an M4A voice recording and need to load it onto an older device that only plays MP3, so you choose MP3. One point to stress: converting a lossy file such as an MP3 to WAV only changes the container. It cannot restore quality that was already lost, and the file simply gets bigger. Output size and processing time depend on the individual file, so we do not quote numbers.

Supported input and known limits

• Only MP3, WAV, M4A, and OGG are offered as outputs. There is no FLAC, bare AAC, WMA, or similar.
• There are no quality settings. Converting between lossy formats (for example MP3 to OGG) compresses again, so quality may drop slightly.
• Whether an input is recognized depends on the bundled ffmpeg core. A file it cannot read, or a format whose encoder is not in the core, ends with 'Conversion failed. Please try a different audio file.' and no further detail.
• The download is always named converted.<extension>. The original file name, and tag data such as title or cover art, are not guaranteed to survive.
• Even when the target format matches the source, the file is re-encoded rather than copied.
• One file per run.
• The whole file is read into browser memory with no size limit, so very large files can be slow or fail.
• The first use needs a network connection to download a core of roughly 25-30MB.

FAQ: Will the quality get worse after converting?

It depends on the source and target. Going from lossless (such as WAV) to lossy (such as MP3) loses some quality; lossy to lossy loses a little more; lossy to WAV does not make it worse, but does not make it better either. There are no quality options, so you cannot adjust this.

FAQ: Why is the WAV file so large?

WAV normally stores uncompressed audio, so its size grows directly with duration and is many times larger than an MP3. If you only want to share or store the audio, MP3 or M4A saves space.

FAQ: Why does it say the conversion failed?

The file may not be valid audio, it may be damaged, the browser may be out of memory, or the core may not recognize the format. Try another file, or convert it to a common format on another device first.

FAQ: Does it need the internet, and is my file uploaded?

The first use needs a connection to download the processing core. The conversion itself does not send your file anywhere. See the section below for details.

Privacy and processing

Conversion happens in your browser. The audio is written to a virtual file system inside the page and processed by a WebAssembly build of ffmpeg, and the code contains no step that uploads it. The only network request is the first-time download of the ffmpeg core from the public CDN unpkg.com, which does not include your file. The result is played and downloaded through a temporary local link that is released when you change files or leave the page.