How to compress MKV files
Upload your MKV file
Drag and drop a file or click to select one. Keep this page open while the file uploads and converts.
Compress the file
NexMedia re-encodes your MKV file on its own servers at the quality you choose. Processing time depends on the file size and how busy the queue is.
Download the compressed file
When the compression finishes, the download appears on this page. Your compressed file is kept for 2 hours, then deleted.
About MKV
the Matroska container, a flexible wrapper that can hold almost any codec
MKV is Matroska, the open-source container that carries video, audio and subtitles in almost any combination. It is the format of media libraries and downloads because it wraps whatever codec the author chose.
An MKV is as large as what is inside it: a full-length film in Matroska carries every byte of its video and audio tracks, plus subtitles and chapters, with no compression of its own.
What compressing MKV does
Compressing an MKV means re-encoding its streams into a leaner encoding such as WebM's VP9; the container changes with it, so extra subtitles and audio tracks are not carried over.
A two-hour film in Matroska at a high bitrate can pass 8 GB; the same film re-encoded for the web commonly lands in the 1–2 GB range.
Settings you can change
Before you compress MKV, you can adjust: Video codec, Rate control, Quality (CRF), Video bitrate, Resolution, Width, Height, Scale fit, Frame rate, Encoder preset, Audio codec, Audio bitrate, Trim start, Trim duration, and Remove metadata.
Limits
Guests can compress files up to 100 megabytes and run 5 conversions per day; a free account raises this to 500 megabytes and 25 per day; paid plans go up to 100 gigabytes.
Your compressed MKV file is kept for 2 hours, then deleted.
Compressing MKV: questions and answers
Will compressing MKV reduce quality?
The container change itself is lossless, but re-encoding the video is not: at a quality-matched bitrate the picture stays close to the original while the size drops sharply.
Can MKV files be compressed without any loss?
The Matroska container copies data without loss, but the video inside is nearly always a lossy encode, and moving it to a smaller encoding means encoding it again.
Which settings can I change when compressing MKV?
You can adjust: Video codec, Rate control, Quality (CRF), Video bitrate, Resolution, Width, Height, Scale fit, Frame rate, Encoder preset, Audio codec, Audio bitrate, Trim start, Trim duration, and Remove metadata. the quality slider governs the re-encode's bitrate, and the resolution control matters when the film will be watched on a phone or laptop screen
How much smaller will my MKV file get?
Re-encoded films routinely shrink by half or more; a high-bitrate archive rip gains the most.
How large a MKV file can I compress for free?
Guests can compress files up to 100 megabytes and run 5 conversions per day; a free account raises this to 500 megabytes and 25 per day; paid plans go up to 100 gigabytes. Your compressed file is kept for 2 hours, then deleted.