Upload a OGG file and get a M4A back. No signup, no watermark, no limit on how many.
OGG here means Vorbis audio in an Ogg container — a patent-free lossy codec that generally beats MP3 at the same bitrate.
Where you run into it: Game audio, Wikipedia and Wikimedia files, Spotify's streaming internals, Linux desktops.
What it costs you: Technical merit never bought it consumer support: plenty of car stereos and older phones simply do not list it.
M4A is an MPEG-4 container holding AAC audio — the same codec as a bare .aac file, wrapped so that players, tags and cover art all behave.
Where you run into it: iTunes and Apple Music purchases, voice memos, Zoom and Teams recordings, most phone-recorded audio.
What it costs you: Outside Apple's ecosystem support is good but not universal, and a few older tools still refuse the extension on sight.
Vorbis and AAC have nothing in common structurally, so the file is decoded to plain audio and encoded again from scratch — a full second generation. Both are efficient codecs of roughly the same era, so at 192 kbps or Best quality the result is a fair match for what you started with. The conversion exists because of a hard compatibility wall rather than a quality question: Apple's platforms do not play Ogg at all, so a file that works everywhere else is simply dead on an iPhone until it becomes something else.
This is the conversion that makes an Ogg usable on an iPhone or iPad. iOS will not play .ogg natively, so the Files app shows it and refuses, and there is no setting that changes that — the file has to become AAC. Worth knowing: a lot of .ogg files people bring here are Telegram voice messages, which are Opus inside an Ogg container rather than Vorbis. They convert exactly the same way, and this is the usual way to get one into a phone's own library or to send it to someone on an iPhone.
Yes, entirely, and there is no cap on how many files you convert. No account, no watermark, no trial.
A little, since both formats are lossy and the audio is encoded a second time. Vorbis and AAC are close enough in efficiency that 192 kbps or Best quality holds the difference below what you are likely to hear on a phone or in a car. From a low-bitrate voice recording the second pass is more noticeable, because there was less to work with in the first place.
Broadly the same for the same perceived quality — you are moving between two codecs of similar efficiency, so there is no dramatic saving in either direction. The MP4 container adds a few kilobytes for its index and tags, and cover art you add later will cost more than the container does.
Yes — M4A is one of the formats this converter writes, so the reverse page exists at /m4a-to-ogg/. Both formats are lossy, so every leg re-encodes: going out and coming back costs two more generations, and the damage accumulates.
The file is uploaded to do the conversion — nothing here runs in your browser — and both your upload and the converted result are deleted the moment the file is sent back. Nothing is stored and nothing is logged beyond the request itself.