Convert between MKV, MP4, MOV, WebM, and AVI video formats. Pick any input and output format from the dropdown — your files never leave your device. Files are converted locally in your browser — nothing is uploaded.
Runs on FFmpeg
Content reviewed October 2026 · About Toolzum
Convert MKV video files to MP4 format directly in your browser. 100% free, private — your files never leave your device.
Converts MP4 files to MKV format — universal video playback on any device to advanced video archiving with multiple subtitle tracks, chapters, and audio streams in one file. All conversion happens locally in your browser with no file size limits.
Convert MP4 video files to MOV format directly in your browser. 100% free, private — your files never leave your device.
Extracts the audio track from uploaded video files (MP4, MOV, AVI, WebM) and encodes it as a high-quality MP3 file. Free to start with no signup.
Reduces MP4, MOV, and WebM video file sizes with a configurable CRF 20–40 slider (default 28, libx264 fast preset), plus a GIF mode with color-palette control. Videos never leave your device — compression runs locally in your browser with FFmpeg WASM.
You can convert between MKV, MP4, MOV, WebM, and AVI. Pick any input and any output from the dropdowns. Common use cases include MKV to MP4 for universal playback, MP4 to WebM for the web, and MKV to MOV for Final Cut Pro or iMovie.
It depends on the target format. Only MKV output copies the video and audio streams without re-encoding — fast, with quality and size unchanged. MP4, MOV, WebM, and AVI outputs always re-encode (libx264 for MP4/MOV, libvpx for WebM, mpeg4 for AVI), which takes longer and can change quality.
Conversions that target MKV copy the existing streams rather than re-encoding them, so the file size stays roughly the same. To actually shrink a video, use the Video Compressor tool instead, which re-encodes with adjustable quality and target size settings.
When re-encapsulating to a container that supports them — MKV and MOV hold multiple audio tracks, chapters, and subtitle streams — those tracks are carried over. MP4's subtitle support is more limited, so subtitle tracks may not survive a conversion to MP4.
No. All processing runs locally in your browser via FFmpeg — your video never leaves your device, nothing is stored, and there are no file size limits. Your videos are completely private.
Video Compressor
Reduces MP4, MOV, and WebM video file sizes with a configurable CRF 20–40 slider (default 28, libx264 fast preset), plus a GIF mode with color-palette control. Videos never leave your device — compression runs locally in your browser with FFmpeg WASM.
Video to GIF
Convert MP4/WebM to GIF animations. Videos up to 250MB. Videos never leave your device — compression and conversion run locally in your browser with FFmpeg WASM.
Video to MP3 Converter
Extracts the audio track from uploaded video files (MP4, MOV, AVI, WebM) and encodes it as a high-quality MP3 file. Free to start with no signup.