Convert FLV to MKV Online Free
FLV is a legacy Flash video format that is now largely obsolete. MKV is a flexible open container that can hold multiple video, audio, and subtitle tracks. FileConverter turns your FLV into MKV online in seconds - free, privacy-first, and with no software to install or account to create.
Convert FLV to MKV
MKV is already selected. Add your FLV file to start.
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Images
Videos
Audio
Add a FLV file above to start the conversion.
Converting FLV to MKV is a solid archival strategy for rescued Flash video: the open Matroska container is well-documented, plays everywhere via VLC, and will not become another dead format holding your footage hostage.
What changes when you convert FLV to MKV
This re-encodes your footage from the FLV container into MKV, which can change the underlying codec and file size. At sensible settings quality is well preserved, but converting from a higher-quality FLV source always produces a better MKV result. Trim long clips first if you only need part of the footage.
About the FLV format
FLV was the standard for streaming Flash video in the 2000s. With Flash discontinued, converting FLV to MP4 is usually necessary to play these files on modern devices and browsers. In everyday use, FLV is chosen for recovering old Flash-era recordings and archives from legacy streaming sites. It opens in VLC and legacy players only.
About the MKV format
Matroska is popular for high-quality films and archives because it can bundle many audio languages, subtitle tracks, and chapters in one file. It is great for storage but not natively supported by many phones or web players. In everyday use, MKV is chosen for high-quality film archives and multi-language and multi-subtitle collections. It opens in VLC and most desktop media players.
FLV vs MKV
FLV is best known for small files for early web streaming, while MKV stands out for stores multiple audio, video, and subtitle tracks. Choosing between them comes down to where the file needs to go next.
Common use cases
People convert FLV to MKV for jobs such as high-quality film archives and multi-language and multi-subtitle collections. It is especially common when a FLV file arrives from one system but needs to work in another that standardises on MKV.
When to convert FLV to MKV
Reach for FLV to MKV when your destination expects MKV — for example high-quality film archives and multi-language and multi-subtitle collections. It is the right move when you receive a FLV file but the app, website, or person you are working with cannot use it. Bear in mind that limited native support on mobile and browsers, so keep your original FLV if you might need it again.
How to convert FLV to MKV
- Upload your FLV file to the converter at the top of this page - MKV is already selected as the output.
- Check the size limit shown on this page, then drag and drop or browse for your file.
- Confirm MKV is still the target format, or pick a different one from the grid.
- Start the conversion and download your MKV file the moment it is ready.
Quality tips
Keep one master FLV archived and convert copies. If the MKV file is for web playback, test it in the target browser or player; if you only need the sound, use our Extract Audio tool instead of a full video conversion.
Platform compatibility
The FLV to MKV converter runs on Windows, macOS, Linux, Android, and iOS - anywhere with a modern browser, with no plugins or permissions required. Once exported, MKV opens in VLC and most desktop media players.
File size limits
Video/audio up to 2GB
Troubleshooting
- If the file exceeds the limit shown below, compress images, trim video, or split archives before retrying.
- If conversion fails, confirm the extension matches the real format — renaming a file alone does not change its contents.
- Very large videos process faster if you trim them first with our Video Trim tool.
- If quality looks soft, try a less aggressive setting when the converter offers options.
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