How do I convert MKV to Opus?

Add your MKV 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 512 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.

VideoAdjustable qualityRuns in your browser

MKV to Opus Converter

Turn MKV files into Opus in a couple of clicks. Flexible container that holds any codec, subtitles and tracks. 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

MKV files (.mkv) · up to 512 MB each

or paste files from your clipboard

Ready when you are

Drop a MKV 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 MKV 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.

MKV and Opus explained

Matroska is a container designed to hold essentially anything: any codec, unlimited audio tracks, subtitle tracks, chapters and attachments in one file. It is the format of choice for archiving films with multiple languages.

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 MKV files come from: Media archives, anime and film collections, and high-quality recordings.
Where Opus is used: Voice and video calls, modern podcast pipelines and WebRTC.

MKV vs Opus

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

MKV compared with Opus
Property	Source	Target
Compression	Container (depends on codec)	Lossy
Animation	Yes	—
Introduced	2002	2012
Browser support	Great in VLC and media servers, poor in browsers.	Modern browsers and apps; older hardware may not.

MKV is stronger at: Holds any codec. Unlimited audio, subtitle and chapter tracks. Open and well documented.
Opus is stronger at: Best-in-class quality at low bitrates. Extremely low latency, which is why calls use it. Royalty-free.

Why convert MKV to Opus?

This is not really a format swap — it is extraction. An MKV file carries a video track and an audio track side by side, and converting to Opus discards the picture and keeps the sound. People do it to turn a lecture, interview, podcast recording or music video into something they can listen to without the video, at a fraction of the file size.

MKV limitations that prompt the switch: Browsers will not play it. Many TVs, phones and editors reject it. Not accepted by social platforms.
What you give up: Older hardware and car stereos generally cannot play it. Less recognised by users than MP3.

Does converting MKV to Opus reduce quality?

MKV stores your data exactly; Opus does not. Some detail is discarded permanently in exchange for a much smaller file, which is usually the right trade for sharing and publishing. Keep your MKV original if it is the only copy — the conversion cannot be undone.