16 best free MKV to MP4 converters [Windows/Mac]

Why I picked it: it is the industry gold standard for free desktop conversion, giving users professional-grade control over codecs and quality settings.

HandBrake is completely free and open-source, and it is the converter I would always turn to if I need granular control over the final MP4 file at no cost. It allows me to specify bitrates, frame rates, and advanced encoder settings (like H.265 or VP9) that most simple tools don't even touch.

On the downside, the interface is far more complex than a typical consumer application, and I found the conversion times were significantly slower, especially without dedicated GPU acceleration for certain codecs. However, this may not entirely be a problem for some, considering it offers so much value at no cost.

Meanwhile, HandBrake relies on its large community of contributors, so updates are frequent but incremental. Recently, I've seen pushes to update the internal encoding libraries like FFmpeg and x265, which means improved performance and better stability for modern high-efficiency video. While these aren't flashy UI changes, they are critical under-the-hood improvements that ensure the output MP4 files are compliant across all devices.

Why I picked it: it’s an essential media player that surprisingly includes a reliable and quick built-in MKV to MP4 converter feature.

VLC has earned its reputation over the years, and one thing I still appreciate is how easily I can convert files without installing anything extra; I just go to the Media menu and select Convert/Save. While it's extremely fast and completely free, I found that its conversion feature is much less reliable than a dedicated tool, especially with unusual codecs. The output options are basic, and I often had to fiddle with the custom settings to get a successful MP4, which can be frustrating.

For a media player, VLC is continually updated, which is why it stays so relevant. The most recent version focused on stabilizing playback for 8K video and improving compatibility with complex HDR and 10-bit color video profiles, changes that directly benefit the quality of my MKV to MP4 conversion when dealing with high-end source files. It’s comforting to know that even though the conversion tool is basic, the underlying codec support is always up to date.

Why I picked it: its Level-3 hardware acceleration keeps 4K conversions stable and fast. The GPU optimization also produced some of the quickest high-resolution conversions during testing.

I tested VideoProc Converter specifically on a 4K MKV file, and its performance was impressive; it utilizes Level-3 Hardware Acceleration, which allows it to process high-resolution video quickly. Its interface feels slightly more complex than some others, packing in a downloader, recorder, and basic editor alongside the converter.

In its latest iteration, VideoProc has heavily leaned into AI features, incorporating tools like a new video stabilization engine and an enhanced noise reduction feature. While I mainly use it for converting, these extras give it versatility. I also noticed that the company has focused on improving support for newer NVIDIA and AMD cards, which ensures maximum GPU usage and keeps those 4K conversion speeds fast.

Why I picked it: this tool stands out for its beginner-friendly layout. It offers an incredibly clean, simple interface and extensive format support for a free desktop tool, making it highly accessible.

Freemake was one of the first free MKV to MP4 converters I used years ago, and I still appreciate its simplicity; you only have to drag and drop your MKV, select MP4, and hit convert – it’s that easy. However, it is important to note that the free version is heavily limited. It often adds a splash screen or watermark to the converted videos, and I had to be careful during installation to avoid bundled adware.

Meanwhile, Freemake’s conversion speed is decent, but it doesn’t compete with modern GPU-accelerated tools. Likewise, the core functionality hasn't changed drastically in recent years, though the team has focused on making batch conversion more stable, especially for large queues that used to freeze. They've also updated their one-click presets for popular social media platforms, ensuring my converted MP4 files are optimized for the latest Instagram and TikTok requirements.

Why I picked it: it is renowned for its exceptional stability and proprietary GPU acceleration, now enhanced with AI tools for superior video processing.

The Winxvideo AI, formerly known as WinX HD Video Converter Deluxe, was recently rebranded to reflect its expanded features. Regardless, it still maintains its reputation for stability, rarely crashing during demanding MKV to MP4 jobs thanks to powerful hardware-acceleration support.

Beyond standard conversion, it now integrates AI tools, such as an AI upscaler and stabilizer, which I found useful for cleaning up video quality before or after conversion. It continues to boast a vast library of device-specific presets for iPhones, Samsung, and other gadgets, which saves me time figuring out the right bitrate.

Meanwhile, Winxvideo AI recently released an update focusing on improving its HEVC/H.265 encoding efficiency. This is vital because many MKV files use H.265, and optimizing that conversion results in smaller, higher-quality MP4 files without sacrificing speed. The AI enhancements also make it a more comprehensive video utility.

Why I picked it: it is specifically optimized for Apple hardware, offering unparalleled speed and stability for Mac users.

When I need to convert MKV files on my Mac, I look for tools optimized for the Apple silicon architecture, and MacX Video Converter Pro delivers. It utilizes Mac's unique GPU acceleration (Intel QSV, AMD, and M-series chips) to speed up conversion times. I found its best feature to be the ability to download videos directly from YouTube and then instantly convert them to MP4 in one flow.

The developers have continuously refined the software for the latest macOS environments, ensuring seamless performance on M-series chips. Their recent focus has been on improving the download speed and stability of their integrated web video downloader, which saves time when grabbing a source video from a site like Vimeo before the MKV to MP4 step. I also noticed they added more presets tailored for the latest iPhone and Apple TV models.

Why I picked it: a veteran free converter that supports almost every multimedia format imaginable, including legacy files.

Format Factory is the definition of a comprehensive free MKV to MP4 converter. I've used it to convert everything from obscure video formats to disc images, and it handles them all. The interface is definitely dated, considering it feels like a utility from the Windows XP era, but the functionality is top-notch.

Because it relies heavily on CPU and open-source codecs, I found its conversion times to be much slower compared to modern, GPU-accelerated programs. Also, like many older free tools, I had to watch out for bundled software during installation.

Furthermore, Format Factory may look outdated, but it’s still being maintained. Recent updates focus on stability for Windows 11 rather than new features, and the team continues to refresh its bundled codecs to avoid errors with newer video standards. That steady maintenance is exactly why it still holds a place on my list for legacy conversions.

Why I picked it: it's a highly technical and powerful free converter that gives true experts infinite control over every encoding parameter.

MediaCoder is essentially a front-end for various open-source encoders. If you know exactly which encoder you want to use (H.264, H.265, FFmpeg, etc.) and what parameters to set, this tool is fantastic. However, I found the sheer number of tabs and options overwhelming, and I almost always had to look up a tutorial just to start a simple MKV to MP4 conversion. While it’s free for personal use, it also doesn’t have the streamlined performance of paid, optimized converters.

Likewise, the updates for MediaCoder are highly technical and often involve integrating the absolute latest builds of core open-source encoders. For example, recent packages have seen fine-tuning for VP9 and AV1 encoding, allowing experts to test cutting-edge compression ratios. This constant integration of bleeding-edge codecs is its main strength, even if it requires me to look up the parameters every time I want to use them.

Why I picked it: A classic, lightweight, and completely free tool that is still surprisingly reliable for basic, small-batch conversions on older Mac and Windows systems.

Although it hasn't seen a major update in years, MPEG Streamclip still works well for quick, standard definition (SD) MKV to MP4 conversions. Its main appeal to me is its tiny file size and the fact that it runs smoothly on older operating systems where newer, resource-heavy programs might struggle. I wouldn't recommend it for modern 4K or HEVC files, as it lacks support for modern codecs and hardware acceleration.

It’s also important to note that this software is mostly abandoned, so there are no formal "new updates" to report. However, I consider its continued stability on old machines a feature in itself. The fact that the last major version remains functional for basic multiplexing tasks on older Mac OS X and Windows XP/7 machines is a testament to its original robust design. This makes it a great solution for anyone running a legacy setup.

Why I picked it: it’s a versatile online tool that handles massive file types beyond video, making it a great all-in-one resource for quick conversions.

When I need to convert a small MKV file without downloading any software, OnlineConvert.com is one of my top choices. It supports not just video, but audio, documents, e-books, and even CAD files. I like the option to adjust the screen size or frame rate directly on the upload page before starting the MKV to MP4 job. However, the file size limits are strict (usually 100 MB-200 MB for the free version), and I found the page to be quite heavy on ads, which slows down the workflow compared to a clean desktop interface.

On the upside, the developers have recently focused on improving their queue management and server infrastructure, which means my conversion times are more consistent and less prone to stalling during peak traffic. They also continually update their security protocols and file deletion policies, which gives me more confidence when uploading sensitive video files to their servers.

Why I picked it: its cloud integration stands out. Pulling MKV files directly from Google Drive or Dropbox speeds up the workflow when you're already working in the cloud.

Convertio is perhaps the most professional-looking of the free online converters I've tested. The drag-and-drop mechanism is smooth, and I appreciate the ability to pull files directly from Google Drive or Dropbox, a huge time-saver.

For a free MKV to MP4 conversion, it limits me to 10 files per day and a maximum size of 100 MB per file, which means it’s completely irrelevant for 4K video. Also, while its conversion is fast for small files, it doesn't compare to the instant feedback of a desktop tool.

I’ve seen previous updates focused on optimizing their internal API for better handling of multi-part video streams, which is important when dealing with complex MKV files that have multiple audio and subtitle tracks. They also added more language support and continuously improved the file retrieval system to ensure my converted files are available quickly after the job is complete.

Why I picked it: it excels at high-quality conversion for obscure codecs and includes advanced output controls, making it the most 'pro' of the online free MKV to MP4 tools.

CloudConvert is the online converter I use when other web tools fail, and I mean that with all seriousness. The tool prides itself on quality, allowing me to adjust complex parameters like the codec profile, CRF (constant rate factor), and tune settings, controls that are usually only available on desktop programs like HandBrake.

I also found their free usage limits to be slightly more generous than others, based on "conversion minutes" instead of just file size, which offers a bit more flexibility. Still, when I tried to convert a large MKV, it quickly ate up my free minutes.

However, CloudConvert announced a major back-end upgrade to its server architecture last year, specifically designed to reduce wait times during peak hours. This directly addresses one of my biggest complaints about online converters: speed inconsistency. They've also been expanding their library of specific video conversion profiles, which is helpful when trying to get a perfect output for an uncommon device.

Why I picked it: Its email-delivery workflow is ideal for simple, hands-off conversions. It lets you upload a file, close the tab, and get the MP4 in your inbox without babysitting the process.

Zamzar’s workflow is unique: upload your MKV, select MP4, enter your email, and the converted file is sent to your inbox. This simplicity is great, but the trade-off is that I have to wait for the email, and the maximum free file size is limited to 50 MB, which is tiny for modern video.

I also find the conversion speed to be mediocre, and the lack of a direct download link makes the process feel outdated compared to modern instant-download tools. It is entirely free up to that 50 MB limit, though.

For such a legacy service, Zamzar is surprisingly diligent about security and file integrity, which is a major upside in my book. Recent updates have focused on strengthening the email delivery system, ensuring that download links don't expire prematurely and are securely sent. They've also focused on improving their virus scanning of uploaded files, which is a reassuring layer of protection when dealing with external content.

Why I picked it: It offers a generous 1 GB maximum file size limit on the free plan, making it one of the most flexible online tools for video.

When I need to convert a 500 MB MKV file and don't want to pay, FreeConvert.com is my immediate fallback. I mean, why not? Its 1 GB limit for the free plan is far more generous than its competitors like Convertio (100 MB) or Zamzar (50 MB). The conversion interface is also straightforward, allowing me to adjust basic options like aspect ratio and video bitrate in one click. 

The downside, which I noticed while testing, is that the conversion speed can fluctuate wildly, often taking much longer than advertised, especially during peak usage. To combat the speed inconsistency, the FreeConvert team has been adding more server capacity to handle the heavy load from users uploading large files under the 1 GB limit. 

Meanwhile, they've also been improving the conversion algorithms for popular formats like MP4, which has led to better stability and slightly faster average speeds, even on the free tier.