Upload a OGG file and get a AAC 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.
AAC is MP3's designated successor and wins at low bitrates by a clear margin. A bare .aac file is the raw ADTS stream rather than the .m4a container most software expects.
Where you run into it: YouTube and streaming audio tracks, broadcast, anything that came out of a device rather than a music shop.
What it costs you: The naked .aac extension confuses a surprising amount of software, which is the usual reason people convert it.
The Ogg is decoded and re-encoded as a bare AAC stream — frames with no container, which is what ADTS means. Two unrelated lossy codecs, so it is a genuine second generation, and 192 kbps or Best quality is what keeps it honest. Unlike the M4A route, nothing here gives the file a duration, a seek table or a place to put tags, so the result is meant to be fed to something rather than listened to directly.
There is one good reason to want this rather than M4A: something downstream expects an ADTS stream, which in practice means broadcast and streaming tooling — HLS segmenters, encoders that concatenate raw frames, hardware that reads a stream off a wire. Before you convert, check whether that tooling takes Opus directly. A great many .ogg files in circulation are already Opus rather than Vorbis, and modern streaming stacks often accept Opus as-is, which lets you skip this generation entirely.
Yes, entirely, and there is no cap on how many files you convert. No account, no watermark, no trial.
A little, as with any lossy-to-lossy transcode. Vorbis is strong in the middle of the range, so give the AAC encoder room — 192 kbps or Best quality — rather than matching the source's number and quietly losing ground. If this file is going into an encoder further down a pipeline, remember that will be a third generation.
Close to the source at comparable quality, and a raw stream carries no container overhead at all, so it can come out marginally smaller than an equivalent .m4a of the same audio. That saving is the tags and the index you are not getting.
Yes, and you can do it on this page: the converter writes OGG as well, so upload the AAC and choose OGG as the output. There is no separate page for that direction. 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.