OneTaskBy Tim King · Updated
OPUS to MP3
Messaging App Recordings From WhatsApp and Telegram Re-encoded as Standard MP3
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How the OPUS To MP3 works
Drop in an .opus file, such as a WhatsApp or Telegram voice note or a Discord recording, and download it as an MP3. This Opus to MP3 converter decodes the audio with your browser's built-in Opus decoder and encodes it in the same tab. Nothing is uploaded, so private messages stay private.
Opus to MP3: a modern codec to the universal one
Opus is a royalty-free lossy codec standardised by the IETF in 2012. It was designed for live voice and music over the internet, so it sounds good at very low bit rates: a WhatsApp voice note is typically 16 to 32 kbps mono, and speech at that rate is clear. MP3 is about 30 years older and needs far more bits for the same quality, but almost every device, editor and upload form accepts it. Converting Opus to MP3 trades file size for compatibility.
What changes in the transcode
- File size grows. A 24 kbps voice note becomes 128 kbps at minimum, so the MP3 is five or more times larger. That is normal and not wasted quality, just MP3's lower efficiency.
- A second generation of loss. Both codecs are lossy, but at 128 kbps MP3 is transparent for speech, so the extra loss is inaudible on voice notes.
- Sample rate. Opus always decodes at 48 kHz internally; the browser then works at its audio rate, and the MP3 is encoded at that rate.
- Bit rate choice. 128 kbps suits voice notes. Use 192 or 320 kbps only for Opus music files encoded above about 96 kbps.
Browser support for Opus decoding
Opus in Ogg (.opus) decodes in Chrome, Edge, Firefox, Opera and Samsung Internet on all platforms. Safari decodes Opus in WebM and CAF containers on recent macOS and iOS, and .opus files from Safari 17 onward, but older Apple devices refuse them. If Safari cannot open the file, use Chrome or Firefox.
How to read the stats
Source shows channels, the decoded rate, seconds and the file's size. Output is the MP3 bit rate and Output size estimates the MP3. Voice notes are mono, so check that the Source line reads 1 ch.
Vorbis files go through OGG to MP3, browser recordings through WebM to MP3, and iPhone audio through M4A to MP3.
FAQ
How do I convert a WhatsApp voice note to MP3?
Export or save the voice note so it appears as an .opus file, then drop it on this page and click export. On Android the files are in the WhatsApp Voice Notes folder; on desktop, right-click the note and choose download. The MP3 is created in your browser.
Why is the MP3 so much bigger than the Opus file?
Opus is far more efficient than MP3, especially for speech. A voice note at 24 kbps becomes at least 128 kbps as MP3, so the file is several times larger even though the sound is the same. The size line shows the expected result.
Why will Safari not open my .opus file?
Older versions of Safari could not decode Opus inside an Ogg container, which is what .opus files use. Safari 17 and later handle most of them. On older iPhones or Macs, open this page in Chrome or Firefox instead and the conversion works normally.
Is my voice note uploaded anywhere?
No. The file is decoded, processed and encoded inside your browser with the Web Audio API. Nothing is sent to a server, so it works offline once the page has loaded and your audio stays private.
See also: all Audio & Video tools, Units, Images, Documents, Data & Code.
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