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MP3 Converter
MP3 Converter — Convert Audio Files to MP3 Online
Drop in a WAV, M4A, AAC, FLAC, OGG, Opus or WMA file and get an MP3 at the bitrate you choose.
Nothing is enforced, but whatever you drop is decoded to 32-bit float in this tab — roughly 20 MB per minute of 44.1 kHz stereo, and more than twenty times the size of a compressed source — before the MP3 encode starts.
About MP3 Converter
MP3 is thirty years old, technically beaten by every codec that came after it, and still the only audio format you can hand to a stranger without asking what their device supports. That is what this page is for: one drop zone that takes the formats people actually end up with — WAV from a recorder, M4A from an iPhone, AAC from a stream, FLAC from an archive, OGG from a game or a Bandcamp download, Opus from a messaging app, WMA from an old Windows library — and writes an MP3 you can send anywhere. Pick the bitrate to match the material: 128 kbps for speech and voice memos, 192 kbps as a sensible default, 256 or 320 kbps for music you care about. Every conversion here is a decode followed by a fresh encode, never a rewrap, because MP3 cannot hold any other codec's data. When the source is lossless — WAV or FLAC — that is one clean generation of loss and 320 kbps gets you close to transparent. When the source is already lossy, the encode stacks a second generation on the first, which is unavoidable and worth spending a higher bitrate on. The browser decodes what it can through the Web Audio API; for the formats it cannot open, an FFmpeg engine served from this site takes over. The lamejs encoder writes the MP3. All of it happens in this tab.
Questions
Which formats can I convert to MP3 here?
WAV, M4A, AAC, FLAC, OGG, Opus and WMA, plus MP3 itself if you want to re-encode at a different bitrate. If you have audio inside a video file, the audio extractor handles that instead — this page takes audio files.
What bitrate should I choose?
128 kbps for speech, voice memos and podcasts. 192 kbps as a general-purpose default. 256 or 320 kbps for music you care about, and especially when the source is lossless, because that is the one case where a high bitrate genuinely buys you something.
Can I make an existing MP3 smaller?
Yes — drop it in and pick a lower bitrate. Be aware that this is a second lossy pass over already-lossy audio, so it degrades more than the size drop suggests. It is worth doing to fit a size limit and not worth doing for tidiness.
Why is the MP3 sometimes bigger than the file I dropped?
Because the source was compressed harder than the bitrate you picked. A 24 kbps Opus voice note or a 96 kbps AAC stream will grow at 192 kbps. Match the source's bitrate rather than exceeding it if size is what matters — going higher cannot add back detail that is not there.
Does the MP3 keep the original file's tags?
No. Every arm here works on decoded audio, and the FFmpeg arm additionally drops attached pictures, so artist, album, track number and cover art do not survive the conversion. The audio does. Add the tags back in your music player or a dedicated tag editor once you have the MP3.
Do I need to install or sign up for anything?
No. The MP3 is written by the lamejs encoder that ships with the page, and for the formats your browser cannot decode on its own an FFmpeg build served from this site takes over — a one-time 31 MB download, cached afterwards. Both run inside the tab, and no file is ever sent anywhere.
Is my file uploaded to a server?
No. Transmute processes everything locally in your browser using JavaScript and WebAssembly. Your files never leave your device — there is no server, no upload, no cloud processing.