How to Compress an MKV Video Online
Follow these three simple steps to compress an MKV video. No software installation required.
Select an MKV Video
Choose one MKV file from your device.
Choose Quality and Resolution
Select a video quality level and keep the original resolution or choose a lower output resolution.
Compress and Download
Start compression, compare the original and output file sizes, and download the compressed video.
How Does the MKV Compressor Work?
MKV video compression reduces file size by removing redundant information during re-encoding. CompressFly uses the H.264 codec to retain high visual quality while reducing the amount of data stored in the video. Quality and resolution settings control the balance between output size and visual detail.
CompressFly handles MKV compression with modern browser technology. No files are sent to a server: everything is processed locally in your browser. Smart video compression makes reducing MKV file size simple and free, with no signup required.
What "processed in your browser" means
- Your MKV file is not uploaded to a server.
- Compression runs locally on your device.
- The compressed video is created in your browser and downloaded directly to your device.
MKV Compression FAQs
How do I compress an MKV video online?
Use this online MKV compressor to reduce MKV video file size in three steps: 1. Select one MKV video from your device. 2. Choose the output quality and optional resolution. 3. Compress the video and download the result.
How can I compress an MKV video without losing quality?
Choose the High quality preset to retain as much visual detail as possible. Keep the original resolution when reducing the dimensions is not necessary.
How does the MKV compressor reduce file size?
The compressor re-encodes the MKV video with H.264 at a lower effective bitrate. Bitrate is the main factor that determines file size, while lowering the resolution—for example, from 4K to 1080p—can reduce it further. Everything runs locally in your browser.
How much smaller can an MKV video get?
Some high-bitrate MKV videos can become 50–90% smaller, but this is not guaranteed. MKV files that already use an efficient codec or a low bitrate may shrink much less. The result depends on the source codec, bitrate, resolution, motion, and selected settings.
Is there an MKV file size limit, and is my video uploaded?
Your MKV video is processed locally in your browser and is not uploaded to a server, so there is no server upload limit. The practical limit depends on your device's available memory and processing power, as well as the video's length and resolution.