How to Convert MKV to MP4 So It Plays on Any Device

If you've got a video in MKV — typical of movie and TV rips — and it won't play on your phone, won't upload to a social app, or your smart TV flat-out rejects it, the problem is almost always the container, not the video itself. Converting it to MP4 with PullVid's MKV to MP4 converter fixes the compatibility in seconds, with nothing to install.

Why MKV causes trouble outside your computer

MKV is a very capable container — it supports multiple audio tracks, embedded subtitles, and pretty much any video codec — but that flexibility has a cost: many phones, smart TVs, editing apps, and social platforms simply don't recognize it or reject it on upload, even when the video inside would play back just fine. MP4, on the other hand, is the container all of those places expect.

Instant remux or re-encode: it depends on what's inside your MKV

Our converter first checks which codecs your video actually uses. If it already carries H.264 video and AAC or MP3 audio — the most common case — it simply repackages that same data into an MP4 container without touching it: an instant remux, done in seconds even for multi-GB files, with quality identical to the source. If instead the MKV uses a different video codec (HEVC, VP9...) or audio codec (AC3, DTS...), the converter automatically re-encodes that track to H.264/AAC so the resulting MP4 plays on any device; this takes longer, roughly in proportion to the video's length.

How to convert your MKV to MP4 step by step

1. Open the MKV to MP4 converter and choose the file from your device.
2. Tap 'Convert'. The first time, your browser downloads the conversion engine (a few MB); after that it's faster.
3. Wait for the bar to reach 100%: if your MKV was already H.264/AAC it'll only take a few seconds; otherwise it'll take a bit longer because it's being re-encoded.
4. Download the resulting MP4 with the 'Download result' button.

What survives the conversion and what can get left behind

Video and audio reach the MP4 at the same perceptible quality, whether they're copied or re-encoded. What does not carry over to MP4 are subtitles embedded in ASS/SSA format (common in fansubs, with custom colors and positioning) or extra audio tracks in other languages: the MP4 keeps only the file's first audio track. If you need to keep subtitles or multiple languages, hold on to the original MKV as well.

Honest limits to know about

Everything runs in your own browser, so the real limit is your device's memory and processing power, not an artificial cap on our end. With very large files (several GB) or long videos that need re-encoding, a computer will be faster than a phone; the process handles one file at a time on a single thread, so be patient with hours-long videos.

If your video comes in a different format

The same kind of conversion (remux or re-encode depending on the codec) also applies to converting an iPhone MOV to MP4. If you'd rather compare the two containers before deciding, see MP4 vs MKV: which one to choose, and if you don't have the video yet, check how to convert a video to MP4 or grab it with our YouTube video downloader.