Convert Matroska MKV files to MP4 in the browser.
Drag & Drop files here
Up to 2GB · 5 files / batch
Matroska MKV files.
Drop MKV files, pick output quality, and download MP4. FFmpeg runs locally in a Web Worker — your video never uploads. The tool requires an initial, one-time download of a local processing engine (Web Worker). This may take a few moments depending on internet speed, but ensures zero server uploads and total privacy.
Conversions run in your tab with JavaScript — no desktop app required.
Files stay on your device during processing. We do not receive your uploads.
Heavy codecs and AI models run locally via Web Workers and WASM (FFmpeg.wasm, Transformers.js).
Drop MKV files, pick output quality, and download MP4. FFmpeg runs locally in a Web Worker — your video never uploads. The tool requires an initial, one-time download of a local processing engine (Web Worker). This may take a few moments depending on internet speed, but ensures zero server uploads and total privacy.
Very long or 4K sources may exceed browser memory. DRM-protected files cannot be converted. Container quirks may affect audio sync. Processing is 100% offline in your browser — files never leave your device.
Yes. This tool is free convert online with no signup. Processing stays in your browser — no uploads.
You control quality settings. Choose higher quality for no quality loss when converting online.
Every conversion runs inside your browser tab using JavaScript and Web Workers. There is no background server queue and no account is required for core tools.
Your files are never uploaded to FreeConvertKit for processing. Originals, previews, and exports stay on your device unless you choose to download or share them yourself.
When codecs or AI models are needed, WebAssembly modules such as FFmpeg.wasm and Transformers.js execute locally — giving you desktop-class power with absolute file privacy.
Shrink massive video files for easy sharing.
Convert WebM videos to crisp looping GIFs locally.
Hit Discord size limits without a muddy export.