What happens when you convert OPUS to AAC
- The audio is decoded and written as AAC at 192 kbps in an ADTS stream.
- Going from one lossy format to another adds a small generation loss. Choose a bitrate at least as high as the source to keep it inaudible.
How to convert OPUS to AAC online
- Press "Choose OPUS files" and select one or more files, or drag them onto the box. You can add files of any size your device can hold in memory.
- Adjust the settings if you need to: the bitrate controls quality and size. The defaults suit most people.
- Press "Convert to AAC". The first audio or video conversion downloads the converter engine, about 32 MB, which your browser then keeps for next time.
- Save each AAC with its download button. Close the tab and every trace of the files is gone from memory.
Why convert OPUS to AAC?
OPUS files usually come from WhatsApp and Telegram voice notes, Discord and video calls. People convert them to AAC because raw AAC streams are what some broadcasters, podcast tools and hardware players ask for.
In short, OPUS is good at what it was made for, and AAC is the more practical choice when the file has to play on another device or app. OPUS plays in current browsers; many car stereos and older players cannot, while AAC plays in all current browsers and on Apple and Android devices.
How to convert OPUS to AAC on Windows, Mac, iPhone and Android
On Windows
Open this page in Chrome, Edge or Firefox, drag your OPUS files in from File Explorer, and press Convert. Each AAC is saved to your Downloads folder. If you prefer a desktop program, VLC can also convert OPUS to AAC: choose Media, then Convert / Save.
On a Mac
Safari, Chrome and Firefox all work. Drag the OPUS files from Finder onto the drop zone and the AAC files land in Downloads.
On iPhone and iPad
Open the page in Safari and tap Choose OPUS files. You can pick from Photos or from the Files app. The converted AAC appears in Files, in the Downloads folder.
On Android
Open the page in Chrome, tap Choose OPUS files and pick them from Files or your gallery. The AAC is saved to the Download folder, where any file manager can find it. Keep the screen on while a long video converts, because Android may pause a tab in the background.
Best settings for OPUS to AAC
AAC is a lossy format, so the bitrate decides both the sound quality and the file size. Size grows in a straight line with bitrate: double the bitrate and the file doubles.
| Bitrate | Size per minute | Good for |
|---|---|---|
| 320 kbps | about 2.4 MB | the highest quality, for music you will keep |
| 256 kbps | about 1.9 MB | excellent music quality |
| 192 kbps | about 1.4 MB | the default: transparent for most listeners |
| 128 kbps | about 1.0 MB | good for music on the go and for podcasts |
| 96 kbps | about 0.7 MB | speech and audiobooks |
| 64 kbps | about 0.5 MB | voice notes and spoken word only |
The OPUS was already compressed, so pick a bitrate at least as high as the original. Going higher does not add quality back, it only makes the file bigger.
OPUS vs AAC: the differences
| OPUS | AAC | |
|---|---|---|
| Full name | Opus audio | Advanced Audio Coding |
| Type | audio | audio |
| Created by | the Internet Engineering Task Force | the Moving Picture Experts Group |
| First released | 2012 | 1997 |
| Compression | Lossy | Lossy |
| Usually contains | Opus in an Ogg container | AAC audio in a raw ADTS stream |
| In a browser | plays in current browsers; many car stereos and older players cannot | plays in all current browsers and on Apple and Android devices |
| Common uses | WhatsApp and Telegram voice notes, Discord and video calls | iTunes and Apple Music, YouTube audio and streaming |
| MIME type | audio/ogg | audio/aac |
About OPUS and AAC files
What is an OPUS file?
Opus was built for speech and music over the internet, and it holds up at bitrates as low as 16 kbps. Voice messages from WhatsApp and Telegram usually arrive as Opus files.
What is an AAC file?
AAC was designed as the successor to MP3 and sounds better at the same bitrate, especially below 128 kbps. A bare .aac file is a raw stream with no chapters or cover art; the same audio in a container is usually called M4A.
OPUS to AAC not working? Common problems
- The conversion is slow. Audio and container changes take seconds, but re-encoding video runs on your own processor. Lower the resolution to 720p, close other tabs, and keep the device plugged in.
- The tab stops or reloads on a very large file. Browsers limit how much memory one tab can use, around 2 GB and less on phones. Split long recordings or convert them on a computer.
- Song titles are missing. Tags such as title and artist are copied when AAC can store them, but cover art is not carried over.
Convert OPUS to AAC with ffmpeg
This converter runs ffmpeg inside your browser. If you would rather use the ffmpeg command line on your own computer, this command produces an equivalent AAC with the same kind of settings:
ffmpeg -i input.opus -vn -c:a aac -b:a 192k -f adts output.aacReplace input.opus with the name of your file. For a whole folder of OPUS files, run the command in a loop, or drop them all on the converter above, which processes them one after another.
OPUS to AAC converter FAQ
Will I lose quality converting OPUS to AAC?
A little. Both formats are lossy, so re-encoding compounds the loss slightly. Keep the default bitrate or higher and the difference is rarely noticeable.
Why is the AAC a different size from the OPUS?
It depends on the settings. At the defaults, the AAC usually comes out close in size to the OPUS; lower the bitrate for a smaller file.
Are my OPUS files uploaded anywhere?
No. The conversion runs inside this browser tab using ffmpeg compiled to WebAssembly, so your files stay on your device. You can disconnect from the internet after the page and converter engine have loaded and it still works.
Can I convert several OPUS files to AAC at once?
Yes. Select or drop as many files as you like; they are converted one after another and each gets its own download button.
How do I open an AAC file?
AAC plays in all current browsers and on Apple and Android devices. AAC is common for iTunes and Apple Music, YouTube audio and streaming.
Is this OPUS to AAC converter free?
Yes. There is no sign-up, no watermark and no limit on how many files you convert. The site is paid for by advertising, and because conversions run on your device there is no server cost per file.
Can I convert OPUS to AAC on my phone?
Yes. The converter works in Safari on iPhone and iPad and in Chrome on Android. Converted files are saved to the Downloads folder.