Contents

Part 1. MKV vs MP4: What’s the Difference
Part 2. Convert/Remux MKV to MP4 with Aiseesoft [Fastest Batch Conversion]
1. Aiseesoft Video Converter Ultimate
Part 3. Convert with Free & Open-source Tools
Part 4. The Free Online Way: For Small Files (Online Tools)
Part 5. FAQs of Converting MKV to MP4

9 Ways to Convert MKV to MP4 Fast (Lossless & Free)

October 15, 2026Jenny Ryan

As an open-standard container, MKV (Matroska) is a favorite for cinephiles because it supports multiple audio tracks and subtitles without compromising quality. However, this complexity often leads to compatibility issues with standard media players, editing software, and mobile ecosystems.

To ensure seamless playback, there is a massive demand to convert MKV to MP4, the universal standard. Whether you need to upload videos to the web, edit in Professional suites on PC/Mac, or enjoy movies on iPhone, Android, or tablets, switching MKV to MP4 provides the perfect balance of high quality and broad accessibility.

Part 1. MKV vs MP4: What’s the Difference
Part 2. Convert/Remux MKV to MP4 with Aiseesoft [Fastest Batch Conversion]
1. Aiseesoft Video Converter Ultimate
Part 3. Convert with Free & Open-source Tools
Part 4. The Free Online Way: For Small Files (Online Tools)
Part 5. FAQs of Converting MKV to MP4

Converter	Best For	Speed	Re-encoding Needed?	Batch Mode	Key Benefit
Aiseesoft Video Converter Ultimate	Pro Users: Lossless, Ultra-fast 4K/8K Batch Tasks	120X (Lightning)	No (Supports Direct Remux)	Yes	One-click solution for 4K/8K .mkv to .mp4 batch conversion.
HandBrake	Users needing deep parameter encoding & compression.	Moderate	Yes (Always Re-encodes)	Yes	Totally free; allows detailed parameter tuning.
VLC Media Player	Quick, one-off conversions for users who already have it.	Slow	Yes	No	No installation required if you already use it to play videos.
FFmpeg	Tech-savvy users and CLI automation script writers.	Very fast	No (via -c copy)	Yes	Maximum control, automation, and zero-loss remuxing
Shutter Encoder	Users wanting a visual GUI for FFmpeg remuxing.	Fast	No (via Rewrap)	Yes	Simplifies tasks with an intuitive visual workflow
Aiseesoft Free Online Converter	Users needing a fast, web-based tool for medium files.	Fast (Web)	Yes	Limited	No file size limit, ad-free web interface.
CloudConvert	Converting small files directly from Google Drive/Dropbox.	Server-based	Yes	Limited	Excellent cloud integration; no CPU usage on your PC.
Convertio	Occasional users with very small files (<100MB).	Moderate	Yes	No	Supports a huge variety of rare file formats.
FreeConvert	Free online conversion for files up to 1GB.	Slow	Yes	Limited	Supports files up to 1GB for free, but with heavy ads.

Part 1. MKV vs MP4: What’s the Difference

When converting video files into other formats, it is useful to know about the formats. Multiple audio tracks, subtitles, or even chapters can be included in a single file using the MKV (Matroska Video) container format. MKV is decent at preserving video quality. However, support is limited on most devices or media players, especially on Macs, and in mobile applications. On the other hand, MP4 (MPEG-4 Part 14) is one of the most common and recognized video formats. MP4 is highly compatible with most devices, media players, and online services. An MP4 file is typically smaller than an MKV file and maintains very good video quality. MP4 files are also helpful for sharing or streaming video.

Here are the key differences between MKV and MP4. Let's take a closer look at MKV vs. MP4.

Feature	MKV	MP4
Compatibility	Limited on some devices	Widely supported
File Size	Larger, high-quality	Smaller, efficient
Features	Supports multiple audio, subtitles, and chapters	Basic single audio & subtitles
Best For	High-quality storage, backup	Streaming, sharing, device playback

Understanding these differences helps you decide why converting MKV to MP4 is often necessary, especially for smooth playback on Mac, iPhone, or other devices.

Part 2. Convert/Remux MKV to MP4 with Aiseesoft [Fastest Batch Conversion]

Aiseesoft Video Converter Ultimate

If you need a solution that balances lightning speed with cinematic quality, Aiseesoft Video Converter Ultimate is the industry standard. Unlike basic tools that often crash or degrade your footage, this software is engineered to handle massive 4K/8K MKV libraries with ease. Besides the main feature that helps you convert video formats, this software offers additional functions. You can also use this as an MKV editor. For example, you can trim/crop your videos after converting from MKV to MP4. Enhance the converted MP4 video up to 8K quality with AI. Colorize the B&W video and remove the sound noise after converting MKV to MP4. Download it now and discover more features.

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Steps to convert or remux MKV to MP4 with Aiseesoft Video Converter Ultimate:

Step 1.

Install MKV to MP4 Converter on your computer and click “Add File" under “Video Converter” to upload the MKV file you want to convert. You can also select multiple videos to import.

Step 2.

Click “Output Format” to select MP4 as your destination format.

Step 3.

You can click “Settings” to edit the profile, like video quality, encoder, sample rate, etc. If you want a higher speed, you can enable “Hardware acceleration”. Then, you can click “Convert All” to change MKV into MP4.

Step 4.

If you want to remux the MKV to MP4 without compression and quality loss, you just need to enable “120× Faster Conversion”, which only swaps the MKV container to MP4 without really encoding the video stream.

Just a few seconds later, the original MKV videos will be converted to MP4 files. This best MKV to MP4 conversion software promises that you can transform MKV to MP4 without losing any quality. In addition, the conversion speed is super-fast - beyond your imagination.

Part 3. Convert with Free & Open-source Tools

HandBrake

HandBrake is a powerful, open-source video transcoder that works well when you need to compress large MKV files or optimize videos for devices like an iPhone or Apple TV. For example, you can use it to reduce the size of a 4K MKV video and convert it to MP4 for easier playback on your phone. With the right encoding settings, you can maintain good visual quality while saving storage space. However, HandBrake's advanced settings may take some time to learn, and re-encoding can take a while, especially with large 4K videos.

Steps to transform MKV to MP4 with HandBrake:

Step 1.

Drag your MKV file into HandBrake.

Step 2.

Choose a preset (e.g., "Very Fast 1080p30") from the right panel.

Step 3.

Set the format as “MP4” in the “Summary” tab. Note that you also need to manually change the file extension in the “Save As” tab to “MP4.

Step 4.

Click “Start Encode”.

HandBrake always re-encodes the video. This means it will take more time and use more CPU, but it allows for better compression and fixed frame rates.

VLC Media Player

VLC Media Player is a convenient option for converting MKV files to MP4, especially if you already have it installed. It lets you convert videos without downloading additional software, making it useful for quick format changes. For example, if an MKV file won't play on your TV, you can try converting it to MP4 with VLC. However, its conversion settings are less intuitive than those of dedicated video converters, and the process may take longer for large files.

Steps to turn MKV into MP4 using VLC:

Step 1.

Go to “Media” > “Convert / Save”.

Step 2.

Click “Add” to load your MKV files, then click “Convert / Save”.

Step 3.

Select “Video - H.264 + MP3 (MP4)” from the dropdown.

Step 4.

Click “Start” to transcode your MKV to MP4 video.

FFmpeg

FFmpeg is a free, open-source command-line tool widely used for video transcoding, remuxing, and streaming. It supports a wide range of multimedia formats and codecs, making it a flexible choice for converting MKV files to MP4. When the source streams are compatible with the MP4 container, FFmpeg can remux a file by copying the original audio and video streams without re-encoding, which is usually much faster and preserves the original stream quality. However, it requires command-line input, which may be challenging for beginners.

Steps to convert MKV to MP4 with FFmpeg (Remuxing with no quality loss):

Step 1.

Click the path of your MKV video and replace the path with CMD, then click the “Enter” button. Here, a command line will appear in Command Prompt.

Step 2.

Input this command line: ffmpeg – I “test.mkv” -c copy “test.mp4” (Please replace “test” with your file name.)

Step 3.

Click “Enter” to run the command. You will find an MP4 file appear in the same folder where your original MKV file exists.

Shutter Encoder

Shutter Encoder is a free, open-source converter designed for both video professionals and enthusiasts. Built on top of FFmpeg, it provides a user-friendly graphical interface for incredibly complex tasks. Its biggest strength is its ability to perform "Rewrapping" (Remuxing), which simply takes the video and audio streams out of the MKV container and puts them into an MP4 container without re-encoding the actual video data. This results in zero quality loss and extremely fast processing times.

Steps to change MKV to MP4 with Shutter Encoder:

Step 1.

Open Shutter Encoder.

Step 2.

Click “Browse” to select the MKV file manually or drag and drop your MKV file(s) into the drop zone.

Step 3.

Under the "Choose function" section, scroll down to select "Rewrap".

Step 4.

In the right-hand panel, set the extension to .mp4.

Step 5.

Click "Start function" at the bottom.

Part 4. The Free Online Way: For Small Files (Online Tools)

Aiseesoft Free Video Converter Online

Aiseesoft Free Video Converter Online is a free online tool that lets you quickly convert any video/audio to MOV, MP4, AVI, MKV, and more. With it, you can convert video files on most devices and social media. It also lets you adjust your video/audio bitrate, aspect ratio, resolution, and more. Here are some steps to convert MKV to MP4 using Video Converter Online.

Step 1.

Enter the official page of Aiseesoft Free Video Converter Online and click the “Add a File” button to import your MKV files.

Step 2.

After uploading your MKV file successfully, please select “MP4” on the right side of the interface and click the “Convert” button to start converting.

Step 3.

Wait for a while, your MKV file will be changed to MP4, and you can click the “Download” button to save the MP4 file to your computer.

CloudConvert

CloudConvert is an online file conversion tool that lets you convert MKV videos to MP4 directly in your browser. It supports various video formats, including MKV, MP4, WEBM, and AVI. Depending on the available options, you can also customize settings such as video resolution and quality. However, uploading large video files may take time, and some features may be subject to usage limits. Follow the steps below to convert MKV to MP4 using CloudConvert.

Step 1.

Open the Cloudconvert website using your browser and click “Select File” in the middle of the interface to select your MKV file. Click the drop-down box on the top right to choose the MP4 format you want to output.

Step 2.

You can also click the drop-down box beside the settings icon to choose output format. Then, click “Convert”.

Convertio

Convertio is a free MKV to MP4 conversion tool that lets you convert video and audio quickly. It supports most formats, including MP4, MKV, MOV, AVI, etc. You can use it as long as you have a browser. Here are the steps to convert MKV to MP4 using Convertio.

Step 1.

Open the Convertio website and click the red button in the main interface to select your MKV file.

Step 2.

Click the drop-down button to choose the output format as MP4.

Step 3.

Then, you can click “Convert” to get your MP4 file.

FreeConvert

FreeConvert is another online MKV-to-MP4 conversion tool you can utilize to convert video. It is easy to use, just a few clicks, and you can convert your video successfully. It supports most media formats, including MP4, MKV, AVI, OGG, MP2, MID, and more. Here are some steps to convert MKV to MP4 using FreeConvert.

Step 1.

Click the “Choose Files” button in the middle of the page to upload your MKV file.

Step 2.

Select “MP4” as your output format from the box near the gear icon. Then, click the “Convert” button.

Part 5. FAQs of Converting MKV to MP4

Why is there no sound after converting MKV to MP4?

This usually happens due to an audio codec mismatch. MKV files often use DTS or AC3 audio, which some MP4 players don't support. To fix this, ensure your converter is set to convert audio to AAC or MP3, which are the most compatible formats for MP4 files.

Does converting MKV to MP4 lose quality?

Not if you use Remuxing (also known as "Stream Copy"). Since MKV and MP4 are just containers, tools like Aiseesoft Video Converter Ultimate can simply swap the container without re-encoding the video. If the software forces "Transcoding," you may see a slight dip in quality, but using a high-bitrate setting will make the difference nearly invisible.

How do I convert MKV to MP4 without losing subtitles?

Choose a converter that supports subtitle tracks and allows you to retain or embed them in the output MP4 file. Note that some subtitle formats supported by MKV may need to be converted to a compatible format, such as SRT or a supported subtitle stream.

Conclusion

Converting MKV to MP4 doesn't have to be a choice between speed and quality. While free tools like VLC and HandBrake are great for occasional use, Aiseesoft Video Converter Ultimate provides the most reliable, lossless, and lightning-fast experience for batch tasks. Whether you're optimizing videos for your iPhone or clearing space on your hard drive, this all-in-one solution ensures a perfect result every time. Ready to save time? Download the free trial and experience 120× faster conversion today!

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