RunToolRunAudio Converter
Convert audio files to different formats.
How to Convert Audio Files
Select an audio file
Click the upload area or choose any common audio file — MP3, WAV, OGG, M4A and more.
Pick the output format
Choose MP3, WAV or OGG as the target and start the conversion — it runs in your browser.
Download the converted audio
Save the new file, ready for any player, editor or device.
Compressed, lossless and uncompressed
MP3, AAC and Opus discard detail to save space and cannot get it back. FLAC and ALAC compress without discarding anything, typically to about half the size of the original. WAV and AIFF store samples with no compression at all.
Converting between categories only ever loses or preserves — it never gains. Turning an MP3 into FLAC produces a large file containing exactly the quality of the MP3, and turning a FLAC into MP3 is a permanent reduction.
Every compressed-to-compressed conversion costs a generation
Going from MP3 to AAC decodes the MP3 — artefacts included — and re-encodes with a different codec that spends bits reproducing those artefacts faithfully. The result is worse than either the original or a direct encode from a lossless source.
So convert from the best source available. Where a lossless original exists, encode from it every time rather than converting an existing compressed file.
Choosing a bitrate
For speech — podcasts, lectures, interviews, voice notes — 96 to 128 kbps mono is transparent and produces files small enough to keep indefinitely. For music, 192 kbps and above is where most listeners stop hearing a difference on ordinary equipment.
Higher numbers cannot exceed the source. Encoding a 128 kbps MP3 at 320 kbps produces a large file containing 128 kbps of actual quality, which is the most common wasted setting in audio conversion.
Which format for which purpose
MP3 plays on absolutely everything, including old car stereos and hardware players, which keeps it the safe default. AAC is more efficient at the same bitrate and is standard in the Apple ecosystem and in video. Opus is the most efficient of the three, particularly for speech at low bitrates, and is well supported on the web but not in older hardware.
FLAC is for archiving and for listening on equipment that justifies it. WAV is for editing and for software that demands uncompressed input.
Metadata and channels
Tags — title, artist, album, artwork — are stored differently in each format and may not survive conversion. A converted library that has lost its tags is a library that no longer sorts or displays correctly, which is a bigger practical problem than a small quality difference.
Channel configuration matters too. Converting a mono recording to stereo doubles the size and adds nothing; converting speech recorded in stereo down to mono halves the size and loses nothing meaningful.
Sample rate, and how this runs
44.1 kHz is the CD standard and 48 kHz is standard for video. Converting between them is resampling, which is a small quality cost, so matching the destination's expectation from the start is better than converting twice.
Conversion runs through FFmpeg compiled to WebAssembly in your browser. Interviews, meeting recordings and unreleased music stay on your device, and the single-threaded encoding means a long recording takes real time.