MKV to MP4
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FREE
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Drop your .mkv file here
or click to browse
MKV is the format most movie rips, TV downloads, and anime releases arrive in because Matroska can hold essentially any codec plus multiple audio languages, multiple subtitle tracks, and chapter markers, all in one file. The problem is that this flexibility comes at the cost of universal support: iPhones and iPads have no built-in MKV player at all, most Android video apps handle it inconsistently, smart TVs and streaming sticks are a mixed bag, and browsers cannot play MKV natively in an HTML5 video tag under any circumstances. MP4 with H.264 video and AAC audio, by contrast, is the closest thing to a universal standard — every phone, browser, smart TV, and social platform accepts it without complaint.
Because MKV files can contain a wide range of video codecs — H.264 already, but also HEVC, VP9, or AV1 depending on the source — this converter fully decodes the video stream and re-encodes it as H.264 at CRF (Constant Rate Factor) 23, a setting widely regarded as visually lossless for the overwhelming majority of content, while re-encoding audio as AAC. This full re-encode is slower than a simple remux, but it is what makes the resulting MP4 reliably playable everywhere, regardless of which codec your original MKV happened to use, and it also collapses the file down to a single video track, single audio track, and no subtitle or chapter data, since those are exactly the extras that make MKV incompatible with so many devices in the first place.
FFmpeg decodes your MKV file's default video stream frame by frame — whether it was originally H.264, HEVC, VP9, or AV1 — and re-encodes it using the libx264 encoder at CRF 23, balancing visual quality against output file size. The default audio track is decoded and re-encoded as AAC, the audio codec MP4 expects for broad device compatibility. The -movflags +faststart flag then rewrites the file so its index (moov atom) sits at the beginning rather than the end, letting the MP4 begin streaming in a browser before the entire file has downloaded.
Upload your MKV file
Drag your .mkv video file onto the upload area or click to browse. MKV containers can hold multiple audio and subtitle tracks, but only the default ones will be used.
Let FFmpeg load
The first time you convert on this site, the ~30 MB FFmpeg WebAssembly engine downloads once and is cached for future use.
Click Convert to MP4
FFmpeg decodes the MKV's video stream — whether it was H.264, HEVC, VP9, or AV1 — and re-encodes it as H.264 at CRF 23.
Audio is re-encoded to AAC
The default audio track is converted to AAC, the codec MP4 expects for maximum device compatibility.
Wait for encoding to finish
This is a full re-encode rather than a remux, so processing time depends on video length, resolution, and the original codec — HEVC and AV1 sources take longer to decode.
Download the MP4
Save the finished file to your device once the progress bar completes. Your original MKV is left untouched.
Play or upload it anywhere
The MP4 is ready for any device, browser, video editor, or upload form — including YouTube, Instagram, and messaging apps.
Mobile & iPhone Playback
MKV is not supported by iPhones or many Android apps — convert to MP4 for native playback everywhere.
Social Media Upload
YouTube, Instagram, and TikTok all accept MP4 but not MKV — convert before uploading.
Smart TV Streaming
Most smart TVs and streaming sticks support MP4 natively but struggle with MKV containers.
Video Editing
Import MKV-sourced content into video editors that prefer the widely-supported MP4 format.
Movie Rips
Downloaded movies often come in MKV — convert to MP4 to play on devices without MKV support.
Windows Media Player
Windows Media Player does not support MKV by default — convert to MP4 for seamless playback.
Stream Copy When Possible
When codecs are compatible, the tool uses stream copy (-c copy) for instant conversion with zero quality loss.
H.264 + AAC Encoding
Output uses H.264 and AAC — the most widely compatible codec pair for all devices and platforms.
100% Browser-Based
FFmpeg WebAssembly runs entirely in your browser — no server upload, no privacy risk for your videos.
Fast Start Optimized
-movflags +faststart moves metadata to the file front for immediate streaming without full download.
No File Size Limits
No server means no upload size cap — convert large MKV files without restriction.
Free — No Watermarks
No watermarks on output, no per-file charges. Use free for standard file sizes — sign up free to raise your limit to 80 MB, or upgrade to Pro for 250 MB.
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