MKV to MP4
MKV (Matroska) is a favorite for high-quality video because it can hold nearly any codec, multiple audio tracks, and subtitles in one file. The trouble starts when you try to play it: many TVs, phones, and editing apps either refuse MKV outright or choke on its extra streams. MP4 is the container everything understands. In most MKV files the video is already H.264 or H.265, so converting to MP4 is often just a container remux that copies the streams without touching quality. FluidConvert rewraps your MKV into an MP4 with a compatible audio and video track so it plays on iPhones, smart TVs, Premiere, and web uploads. Only tracks or codecs MP4 can't legally hold get re-encoded. It runs free in your browser with no account and no watermark.
Drop your file here, or browse
Accepts: video/x-matroska, .mkv · Max 1GB · always free
Your files are encrypted with TLS and automatically deleted after conversion.
Simply upload your .MKV file and we'll convert it to .MP4 format — fast, free, and secure.
Fast & Free
Convert files up to 1GB completely free. No account, no limits.
Secure
Files are encrypted and automatically deleted after conversion.
High Quality
Industry-leading conversion with no quality loss.
How to Convert MKV to MP4
Upload Your File
Click the upload area above or drag and drop your .MKV file. We support files up to 1GB, completely free.
Choose Output Format
Select .MP4 as your target format. Adjust any conversion settings if needed.
Download Your File
Click Convert Now and wait a few seconds. Once complete, download your converted file instantly.
About MKV to MP4
Last updated: August 2026
What is MKV?
MKV, short for Matroska Video, is an open-source multimedia container created in 2002. It is not a codec but a wrapper that can store an almost unlimited number of video, audio, subtitle, and chapter tracks inside a single file. That flexibility is why it dominates high-definition movie rips and archival video: you can bundle H.264 or H.265 video with lossless FLAC audio, multiple language tracks, and softcoded subtitles together. The downside is compatibility. Because Matroska is not natively supported by Apple's ecosystem, most hardware media players, or standard mobile video apps, MKV files frequently won't open without dedicated software like VLC.
Why convert to MP4?
MP4 is the most universally supported video container in existence. Every smartphone, browser, smart TV, game console, and social platform plays MP4 without extra software or plugins. If you want to AirDrop a video to an iPhone, upload to YouTube or Instagram, edit in iMovie or Premiere, or simply guarantee a file opens on someone else's device, MP4 is the safe choice. Converting MKV to MP4 strips away the compatibility barrier while keeping the same underlying video. It also drops MKV's extra baggage that many players can't parse, leaving a clean, single-track file that just works everywhere.
What to expect from the conversion
When your MKV already contains H.264 or H.265 video and AAC audio, the conversion can be a lossless remux: the streams are copied straight into an MP4 container with zero quality change and near-instant processing. File size stays essentially identical. If the MKV uses a codec MP4 doesn't support well, such as certain lossless audio or unusual subtitle formats, that track is re-encoded, which is lossy for that stream only. MP4 also can't carry multiple softcoded subtitle tracks the way MKV can, so extra subtitle and chapter data may be dropped. The primary video and audio you actually watch are preserved.
How FluidConvert handles it
Your MKV is processed on secure servers that remux compatible streams directly into MP4 whenever possible, avoiding any quality loss. Uploads are encrypted in transit and automatically deleted from our servers about an hour after processing. There is no watermark, no account, and no cost.
Common reasons to convert MKV to MP4
- Playing an MKV movie rip on an iPhone, iPad, or Apple TV that refuses to open Matroska files
- Uploading an MKV recording to YouTube, Instagram, or a website that only accepts MP4
- Importing high-definition MKV footage into iMovie or Premiere Pro, which don't handle MKV natively
- Streaming an MKV to a smart TV or Roku that shows a codec or format error
- Sharing a downloaded MKV video with someone whose phone or media player can't play Matroska
Frequently Asked Questions
Will converting MKV to MP4 reduce the video quality?
Usually not. Most MKV files already store H.264 or H.265 video, and MP4 supports both, so FluidConvert copies the video stream into the new container without re-encoding it. That is a lossless remux with identical quality and file size. Quality only changes if a specific track, such as a lossless audio format MP4 can't hold, has to be re-encoded to fit the container.
Why won't my MKV file play on my iPhone or smart TV?
Apple devices and most TVs don't natively support the Matroska container, even when the video inside is a standard codec they can decode. The player rejects the file based on its MKV wrapper, not its contents. Converting to MP4 puts the same video into a container those devices recognize, so it plays normally without installing VLC or other third-party apps.
What happens to subtitles and multiple audio tracks in my MKV?
MP4 supports far fewer subtitle and track types than MKV. FluidConvert keeps the main video and audio track. Additional language audio tracks or softcoded subtitle streams that MP4 can't represent may be dropped during conversion. If you need multiple embedded subtitle languages preserved, MKV is actually the better container to keep them in.
How long does an MKV to MP4 conversion take?
When the streams can be remuxed directly, even a full-length HD movie converts in seconds because no re-encoding happens; the data is simply rewrapped. If a track has to be re-encoded to be MP4-compatible, the time depends on the video length and resolution, but audio-only re-encodes are still fast since the video itself is copied untouched.
Is MP4 or MKV better for storing my video collection?
MKV is better for archiving because it can hold multiple audio languages, softcoded subtitles, chapters, and lossless audio in one file. MP4 is better for playback and sharing because it works on virtually every device and platform. A common workflow is keeping MKV masters for storage and converting to MP4 copies whenever you need to play or share a video widely.