How This Audio Converter Works
What this converter does
This tool takes an audio file and re-encodes it into either MP3 or WAV. It accepts a broad range of inputs — MP3, WAV, OGG, AAC, M4A, FLAC, and WebM — and decodes them through the Web Audio API, which turns the compressed source into raw audio samples. From those it writes a fresh file in the format you pick, applying your chosen sample rate and channel layout.
MP3 output is produced by a LAME encoder (lamejs) running as JavaScript, while WAV is written as uncompressed 16-bit PCM. Files up to 500MB are accepted, and the decode-and-encode pass runs on your own device without an upload.
When to use it
Reach for it when a file is in a format your target app or device will not play, or when you want a smaller, more portable copy. A frequent case is converting voice memos or downloaded tracks that arrive as M4A or FLAC into MP3, which nearly every player and phone handles.
It is just as useful in the other direction: exporting a WAV from a compressed source when you need an uncompressed file for editing, or collapsing a stereo track to mono to shrink a spoken-word recording. Tuning bitrate or sample rate to hit a size or quality target is part of the same step.
Example: an M4A voice memo to MP3
Say you have a lecture recorded as a 40MB M4A file. Choose MP3 as the output, set the bitrate to 128 kbps, and switch channels to mono, since speech gains nothing from stereo. The Web Audio API decodes the AAC audio inside the M4A, the LAME encoder re-encodes it at 128 kbps, and the result is a far smaller MP3 that plays anywhere. An estimated size appears before you commit, and the built-in player lets you check it first.
Formats, quality, and edge cases
Output is limited to MP3 and WAV, which cover the compressed-and-portable versus uncompressed-and-editable split most workflows need. The bitrate options (128, 192, 256, and 320 kbps) apply only to MP3; WAV size is governed by sample rate and channel count. Sample rate can be 44.1 kHz (CD standard) or 48 kHz (the usual choice for video).
A few limits are worth knowing. Choosing mono averages the left and right channels, so it cannot be undone. Very large files can exhaust available memory during decoding, so a shorter clip works better. And if a source uses a codec the browser cannot decode, converting it to a common format first usually clears the problem.