How do I convert AAC to Opus?

Add your AAC file to the upload area above, then press Convert. The Opus file downloads straight to your device. You do not need an account, and there is no watermark.

Are my files uploaded to a server?

No. This conversion runs entirely inside your browser using WebAssembly, so the file never leaves your device — you can even disconnect from the internet after the page loads and it will still work.

Does converting to Opus reduce quality?

Opus uses lossy compression, so some data is discarded. At the default quality the difference is very hard to see or hear; raise the quality setting if you need to be certain, at the cost of a larger file.

How large a file can I convert?

Up to 300 MB per file for this conversion. Because the work happens in your browser, the practical limit is your device's memory — larger files work on a desktop with plenty of RAM and may fail on an older phone.

Can I convert several files at once?

Yes. Add as many as you like and press Convert All. Each file is processed independently, so one failure does not stop the rest, and you can download everything together as a ZIP.

Can I use this on my phone?

Yes. FileTools360 works in mobile browsers on iOS and Android, including choosing files straight from your camera roll. Very large videos may run out of memory on a phone — those are better converted on a laptop.

AudioAdjustable qualityRuns in your browser

AAC to Opus Converter

Turn AAC files into Opus in a couple of clicks. The successor to MP3 — better quality per bit. The best low-bitrate codec available — voice and music. The output is re-encoded, so quality depends on the settings you choose.

On your deviceNever uploadedGone when you close the tabHow this works

Drop your files here

AAC files (.aac, .adts) · up to 300 MB each

or paste files from your clipboard

Ready when you are

Drop a AAC file above and FileTools360 will turn it into Opus — right here on your device, without uploading anything.

⌘K to search converters

How to use it

1
Add your AAC files
Drag them onto the upload area, choose them from your device, or paste them from your clipboard. You can queue several at once.
2
Adjust the settings if you want to
The defaults suit most people. Open Advanced to control bitrate, sample rate and channels and start and end times.
3
Convert and download
Press Convert. Everything happens on your own device — nothing is uploaded. Download files one by one, or grab them all as a ZIP.

AAC and Opus explained

AAC is the successor to MP3 and is the default audio codec for MP4 video, Apple Music and YouTube. At the same bitrate it generally sounds noticeably better than MP3.

Opus is the current state of the art for lossy audio, and the codec behind most voice calls you make over the internet. It performs well across an unusually wide range, from 6 kbps speech to transparent music.

Where AAC files come from: Streaming services, video soundtracks and Apple devices.
Where Opus is used: Voice and video calls, modern podcast pipelines and WebRTC.

AAC vs Opus

The two formats solve different problems, which is why converting between them involves trade-offs rather than a straight upgrade.

AAC compared with Opus
Property	Source	Target
Compression	Lossy	Lossy
Introduced	1997	2012
Browser support	Excellent across modern devices.	Modern browsers and apps; older hardware may not.

AAC is stronger at: Better quality per bit than MP3. The standard audio track for MP4 video. Excellent device support.
Opus is stronger at: Best-in-class quality at low bitrates. Extremely low latency, which is why calls use it. Royalty-free.

Why convert AAC to Opus?

People make this switch when they run into the limits of AAC: archiving, or targeting very old playback hardware. Opus is the better fit when voice content, or any situation where bandwidth is tight.

AAC limitations that prompt the switch: Still lossy. Patent licensing applies to encoders. Slightly less universal than MP3 on very old hardware.
What you give up: Older hardware and car stereos generally cannot play it. Less recognised by users than MP3.

Does converting AAC to Opus reduce quality?

Both AAC and Opus are lossy, so this is a re-encode: the file is decoded and compressed again. At the default quality setting the difference is very hard to see, but each successive re-encode compounds. If you will need the file again later, keep the AAC original rather than converting back and forth.