OGG / Opus to MP3 Converter

About the OGG / Opus to MP3 Converter

Ogg files — .ogg, .oga and .opus — hold Opus or Vorbis audio (sometimes FLAC). They are what many chat apps send as voice messages, but plenty of players, car stereos, editors and older phones cannot open them. This page turns them into an MP3 (LAME) or an M4A (AAC) that plays almost everywhere.

It decodes with your browser’s own Opus and Vorbis decoders where it has them, with its Web Audio decoder for FLAC inside Ogg, and otherwise with a WebAssembly decoder that the page downloads only when it is needed — so it works even in browsers without Opus or Vorbis support. Voice notes are recognised (mono, recorded at 16 or 24 kHz) and get a small mono MP3 at the rate they were recorded at; music gets 192 or 320 kbps. Title, artist and album tags are carried over.

Everything happens in your browser: your voice messages and songs are never uploaded. Without a pass, the converted file is a free preview: its first half (up to 30 seconds) with a short MySmartCoPilot chime every 10 seconds.

What is inside an .ogg or .opus file

Ogg (RFC 3533) is a container: the sound inside is usually Opus (RFC 7845 describes Opus in Ogg) or Vorbis (Vorbis I specification), sometimes FLAC, and in old files Speex. The page reads the first pages of the file and shows which it is.

Opus always decodes at 48 kHz, but its header also records the sample rate the recording had (“input sample rate”), and a number of samples to skip at the start (“pre-skip”). Voice messages are usually mono Opus at a low bitrate (the page shows the rate each one was recorded at); Telegram’s Bot API documentation, for example, lists an .OGG file encoded with Opus as a voice-message format, alongside MP3 and M4A.

Which quality to choose

• Voice (mono, 64 kbps): voice notes, interviews and lectures. A minute is about 470 KB.
• Standard (128 kbps): speech in stereo and casual listening.
• High (192 kbps): music; transparent for most listeners on most songs.
• Best (320 kbps MP3, 256 kbps AAC): when the file will be edited or converted again.

The source is already compressed, so converting can only keep or lose quality, never add it: choose a bitrate at least as high as the source’s for music. For MP3 below 32 kHz the standard (ISO/IEC 13818-3) allows at most 160 kbps, and the page adjusts the bitrate if needed.

MP3 or M4A?

MP3 plays on practically every device, car stereo and program. M4A (AAC in MPEG-4) sounds better at the same bitrate and is what iPhones, iTunes, Apple Music and most modern phones prefer; some older devices and car stereos cannot play it.

Limitations

• Speex audio (an old voice codec in some .ogg and .spx files) cannot be decoded in browsers, so those files cannot be converted here.
• Both formats are lossy: the MP3 or M4A is a new compression of the decoded sound, so a very low source bitrate stays audible.
• An Ogg video (Theora) is converted to its sound only.
• One file at a time. The WebAssembly decoder holds the whole decoded file in memory, so very long files may be too large for a phone.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot. The audio engine and the MP3 or AAC encoder download from MySmartCoPilot the first time you convert (a WebAssembly decoder of about 2.4 MB too, only when your browser cannot decode the file). Your audio is never uploaded.