Top 8 AVI to MKV Converters in 2026 (Tested for Windows, Mac & Online)

To get straight to the point, AVI to MKV conversion either preserves compatible streams through remuxing or changes them through re-encoding. The right choice depends on whether you need to preserve quality, fix playback on a target device, or reduce file size.

Convert AVI to MKV: Quick Answer

Before you start: confirm that you are authorized to convert the file and identify the codecs in the AVI. Step 1: remux when the existing video and audio codecs already play on your target device; re-encode when compatibility needs to change.

Step 2: choose MKV as the output container and select a local desktop tool for large or private files, an open-source transcoder for codec control, or an online converter for a small, non-sensitive file.

Step 3: save the MKV, play a short section on the destination device, and keep the original AVI until the result is verified.

Compatibility should be checked before speed or file size: a fast container change preserves the original codec, including one that a TV, Plex client, or media player cannot decode.

AVI vs MKV: Why Convert AVI to MKV?

AVI (Audio Video Interleave) is a Microsoft container from 1992 — still in use but technologically limited. MKV (Matroska) is the modern open-source container that solves most of AVI's problems:

• Multiple subtitle tracks — MKV supports many subtitle streams; AVI is limited
• Multiple audio tracks — MKV holds multiple language tracks cleanly; AVI struggles with more than one
• Modern codec support — MKV holds H.265, AV1, VP9, Opus, and other modern codecs; AVI's codec list is older
• Chapter support — MKV has proper chapter metadata; AVI doesn't
• Flexible playback options — MKV can carry modern streams, but actual playback still depends on the codecs supported by the target player or TV
• Flexible packaging — MKV can preserve compatible streams without re-encoding, though the container alone does not meaningfully reduce file size

The most common reason to convert is preserving an old AVI archive in a more flexible container without changing compatible streams. This is one focused AVI-to-MKV task within broader video format converter workflows. If a device specifically needs MP4 instead, the same compatibility check applies when you convert AVI to MP4.

Choose Your AVI to MKV Method

Use a local converter when you have a large library or private footage. Choose an open-source transcoder when the source codec needs to change. Use an online tool for a small, non-sensitive file when convenience matters more than upload time. A broader free Video Converter guide can help when your task extends beyond AVI and MKV.

For this AVI-specific task, remuxing keeps compatible streams intact; re-encoding changes the video or audio codec for a playback, size, or quality goal.

Fast, Private Desktop AVI to MKV Converters

1. UniFab Video Converter

Platform: Windows, macOS | Price: 0, available at no cost

UniFab Video Converter is a local AVI-to-MKV converter for Windows and macOS, suited to authorized large batches and private footage because files stay on the computer. It has no watermark or daily conversion limit, supports folder-level batch work, and can use NVIDIA, AMD, or Intel GPU acceleration of up to 50× for conversion.

Its lossless remux option can rewrap an AVI as MKV without re-encoding when the existing streams are compatible with the destination device. It is not a fit for Linux-only users, readers who prefer a fully open-source command-line workflow, or someone converting one small non-sensitive file in a browser.

How to Convert AVI to MKV with UniFab:

Step 1: Launch UniFab and select the Converter module. Drag and drop your AVI file or click Add to browse.

Step 2: Select MKV as the output format. Use the lossless option only when the source codecs are compatible with the target player; otherwise choose an appropriate video and audio codec, then click Start.

Best fit: large local batches and private footage that need a straightforward desktop workflow.

Not ideal for: Linux-only users, open-source command-line workflows, or occasional small browser-based conversions.

2. AVS Video Converter

Platform: Windows | Price: Supported format conversion is available at no cost

AVS Video Converter is a Windows-only converter with broad format coverage. Its supported format conversion is available without restrictions. The interface is functional, though it may feel dated for readers who want a newer desktop workflow.

How to Convert AVI to MKV Using AVS Video Converter

1. Step 1: After opening this program on your Windows, head to the top to select the “To MKV” option > select “Browse” > add your preferred AVI video to the tool.
2. Step 2: Once you see the “Profile” drop-down menu, open it and select your appropriate preset. Then, select the “Convert Now” option to start the AVI to MKV conversion process.

Strengths: broad codec support, decent batch features 

Weaknesses: Windows only; the interface may feel dated

Open-Source AVI to MKV Converters

3. HandBrake

Platform: Windows, macOS, Linux | Price: Free (open source)

For AVI to MKV, HandBrake is a free cross-platform transcoder for Windows, macOS, and Linux, with detailed controls covered in this HandBrake Video Converter review. It is useful when the source codec needs conversion, but it always converts video, so it is not the right tool for a lossless video remux.

How to Convert AVI to MKV Using HandBrake

1. Step 1: Once you open this free tool on your Mac, select the “Source” in the upper left side of the screen > Open File.
2. Step 2: Select your required AVI file for conversion > head to the “Destination” > select “Browse” to decide the location to save the converted MKV file.
3. Step 3: Next, select the “Start” option in the main window for completing the conversion process. 

Best fit: codec conversion with detailed controls across Windows, macOS, and Linux.

Not ideal for: a lossless video remux or readers who want the simplest workflow.

4. VLC Media Player

Platform: Windows, macOS, Linux | Price: Free (open source)

VLC includes a free converter buried in Media → Convert/Save. It works, it's already installed on most Macs, and it's free. Quality and format options are limited compared to dedicated converters, and the conversion UI is rough.

How to Convert AVI to MKV Using VLC

1. Step 1: Open the VLC program on your Mac. Then, go to the “Media” menu at the upper left side of the program and select “Convert/ Save.”
2. Step 2: Go for the “Add” option in the menu > add your wanted AVI file for conversion.
3. Step 3: Under the “Output” section, select MKV > select “Convert” to start the AVI to MKV conversion process.

Strengths: already installed, cross-platform 

Weaknesses: limited format options, slower than dedicated tools

Free Online AVI to MKV Converters

5. CloudConvert

CloudConvert is a browser-based AVI-to-MKV option with 10 free conversion credits per day. Your AVI file is uploaded for cloud processing, so it is convenient for small, non-sensitive files but less suitable for large libraries or private footage.

How to Convert AVI to MKV: Go to cloudconvert.com, select AVI to MKV, upload your file, adjust settings if needed, and click Convert.

Best fit: small, non-sensitive files when you do not want to install software.

Weaknesses: cloud upload required, slower than desktop on large files

6. VEED.io

Platform: Online | Plans: Free and paid options

VEED.io is a browser-based editor that includes conversion. Free tier watermarks the output; paid tier removes it. Useful if you want conversion + light editing in one place.

How to Convert AVI to MKV Using Veed.io

1. Step 1: You can open this program using any web browser. Upload your required AVI file to the tool using drag & drop option.
2. Step 2: Otherwise, on your device, select the Blue button to select the AVI file from the folder. You can also add the file from the Dropbox, YouTube URL, etc.
3. Step 3: Once you see the list of file types in the drop-down menu, select MKV as the output format. Then, select the “Convert File” option to begin the conversion process.

Strengths: editing features bundled, no install 

Weaknesses: watermarks on free output, slower than dedicated converters

7. FreeConvert

FreeConvert is a simple multi-tool web platform. Its free allowance includes 20 conversion minutes per day, with a five-minute limit per file, making it a better fit for short clips than long videos.

How to Convert AVI to MKV: Go to freeconvert.com, select AVI to MKV, upload your file or import from cloud storage, adjust settings, and click Convert.

Strengths: clean UI, no watermark on small files 

Weaknesses: the free per-file time limit is restrictive for long videos

8. Converter App

Platform: Online | Price: Free

A lighter web converter for one-off files. Converter App states that AVI-to-MKV conversion is free with no limits and that uploaded files are deleted automatically within 120 minutes. That deletion window is useful context, but cloud upload is still different from keeping private footage local.

How to Convert AVI to MKV Using Converter App

1. Step 1: After opening this tool on your device using any browser, upload the AVI you want to convert to MKV format in the left-side upload box.
2. Step 2: The uploaded AVI file will be automatically converted to the selected MKV format.
3. Step 3: After finishing the auto-conversion, you will see a “Download” option, which you need to select for your desired results.

Strengths: simple, free 

Weaknesses: small format library and cloud upload

AVI to MKV Converter Comparison

Free allowances and deletion details are current as of August 2026.

Remux vs Re-encode: Quality and Compatibility

Choose between remuxing and re-encoding based on the codecs inside the AVI and the device that will play the finished MKV.

Remux (stream copy): The converter places the existing video and audio streams in an MKV container without decoding or re-encoding them. It is typically very fast, preserves the original quality, and leaves file size close to the input.

• When to remux: the existing video and audio codecs already play on the target TV, Plex client, or media player, and you only need a new container.

Re-encode: The converter decodes the AVI streams and creates new video or audio codecs inside MKV. It takes longer than remuxing, and output quality and file size depend on the codec, bitrate or quality setting, resolution, and audio settings.

• When to re-encode: the target device cannot decode the existing streams, or you need different codec, size, or quality settings. A container change preserves the original incompatibility; it cannot repair it.

UniFab Video Converter can use a lossless remux when the source permits it. In FFmpeg, ffmpeg -i input.avi -c copy output.mkv performs stream copy. Test one representative file on the intended player before processing a full library; that small check prevents a fast batch from preserving a codec your destination cannot use.

Settings That Prevent Quality and Size Problems

1. Start with a remux test when the existing codecs are compatible. A container-only change should leave quality and file size nearly unchanged.
2. Set codec and bitrate or quality mode deliberately when re-encoding. These settings, not the MKV container, drive most output-size changes.
3. Avoid unnecessary scaling. Raising resolution during format conversion can enlarge files without restoring missing source detail.
4. Check audio settings, since extra tracks, high bitrates, and uncompressed audio can increase file size.
5. Convert a short sample first and check for motion artifacts, playback failures, and unexpected file growth before running a library.
6. Use correct external-drive paths. Desktop converters and FFmpeg can read AVI files directly from an external drive when the input and output locations are set correctly.
7. Keep the source AVI until the finished MKV plays correctly on the target device.

Conclusion

AVI-to-MKV conversion can be a lossless remux or a full re-encode. Use remux when the existing streams play on the target device, and re-encode when codec compatibility must change. Local processing is generally the better fit for large or private files, while online tools suit small, non-sensitive jobs. For a local batch workflow on Windows or macOS, UniFab Video Converter is a practical option when compatible streams can be remuxed.

AVI to MKV FAQs

How can I check the codecs inside an AVI before converting?

Use a media-information utility or a player that displays codec details, then compare the AVI's video and audio codecs with the formats supported by the destination device. That check helps determine whether a remux is viable or whether re-encoding is needed.

Should I use CRF or bitrate when re-encoding an AVI?

CRF, or Constant Rate Factor, targets a consistent visual quality while allowing file size to vary. A bitrate target makes output size more predictable, but visual quality can vary by scene. For an archive, start with a short sample and choose the result that looks right on the target player.

Does hardware acceleration change AVI-to-MKV quality?

Hardware acceleration primarily affects how quickly a file is processed. Output quality still depends on the codec, quality mode or bitrate, resolution, and audio settings chosen for the conversion.

Where should I save batch-converted MKV files?

Use an output folder that is separate from the source folder and has enough free space for the expected results. Clear naming and a dedicated destination folder make it easier to compare a sample, avoid overwriting originals, and review a completed batch.

Why does a smaller MKV sometimes look worse than the AVI?

A smaller output usually reflects stronger compression, a lower bitrate, or a more aggressive quality setting. Reducing resolution can also remove visible detail. Compare a short, motion-heavy scene before converting a full library, especially when preserving older footage matters.