Choosing an output, briefly
Most people arrive at an online audio converter already knowing the format they need, because something downstream told them. When that is not the case, the decision is short:
- MP3 plays on everything ever made. Pick it when you do not control the other end.
- M4A holds AAC, which sounds better than MP3 at the same bitrate. Pick it for Apple software and modern browsers.
- Opus is the best of the lossy codecs by a clear margin at low bitrates, and excellent at high ones. Pick it when both ends are yours.
- FLAC is lossless and roughly half the size of WAV. Pick it to archive.
- WAV is uncompressed PCM. Pick it because a tool insists, not because it sounds better.
- OGG holds Vorbis. Pick it for game engines and older open-source tooling.
The rule that matters more than the format
Lossy encoding is not reversible, and it stacks. Every time you convert audio format from one lossy codec to another, the second encoder works from what the first one left behind rather than from the original recording, and makes a fresh set of decisions about what to discard. One hop is usually fine. Four hops through a chain of tools is audible.
The practical consequence is about where you keep things, not about which converter you use. Keep the least-compressed version you have as the source, and generate lossy copies from it when a particular device or platform needs one. If all you have is a lossy file, converting it does not make things worse than they already are, but it does not make them better either.
What this one preserves
Sample rate and channel count come through unchanged. Text metadata such as title, artist and album is carried across where both containers support it. Embedded cover art is not, because artwork lives in the file as an image stream and only the audio is kept.
Everything runs on your own machine. The engine is ffmpeg compiled to WebAssembly, fetched once on your first file and then served from your browser cache.