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Convert Flash Video FLV files to Matroska MKV format for modern media player compatibility and efficient long-term video archiving. ChangeThisFile handles conversion with FFmpeg on secure servers.
By ChangeThisFile Team · Last updated: March 2026
ChangeThisFile converts FLV to Matroska using FFmpeg, a professional-grade multimedia framework, to transcode FLV files to Matroska format with optimized codec settings and quality preservation. Free with no signup required. Files are encrypted during transfer and automatically deleted from our servers after conversion.
FLV vs Matroska: Format Comparison
Key differences between the two formats
| Feature | FLV | MKV (Matroska) |
|---|---|---|
| Full Name | Flash Video | Matroska Video |
| Developer | Adobe Systems | Matroska.org |
| Status | Deprecated | Actively maintained |
| Video Codec | H.263, VP6, H.264 | H.264, H.265, VP9, AV1 |
| Audio Codec | MP3, AAC, Nellymoser | AAC, FLAC, AC-3, Opus |
| Subtitle Support | None | SRT, ASS, PGS and more |
| Multiple Tracks | No | Yes (video, audio, subtitles) |
| Modern Media Players | VLC only | VLC, MPC-HC, Kodi, and more |
When to Convert
Common scenarios where this conversion is useful
Flash Archive Migration
Convert legacy FLV video archives to the modern, open Matroska format for long-term preservation and broader media player compatibility.
Kodi and HTPC Media Libraries
Add FLV content to Kodi or other HTPC media center libraries by converting to MKV, which is universally supported by home theater software.
Adding Subtitle Tracks
Convert FLV to MKV to then mux in subtitle tracks (SRT, ASS), taking advantage of Matroska's superior subtitle support.
VLC and Media Player Organization
Organize a large FLV video library in the more modern and widely-recognized MKV format for easier management and playback.
Re-encoding for Better Compression
Convert FLV files to MKV with modern H.265 encoding for significant file size reduction while maintaining or improving quality.
Who Uses This Conversion
Tailored guidance for different workflows
Content Creators
- Convert FLV footage to Matroska for playback in software and devices that expect the Matroska format
- Transform FLV recordings to Matroska to match the format an existing workflow or player requires
Video Editors
- Convert FLV footage to Matroska for importing into editing software like Premiere or DaVinci Resolve
- Transform FLV project exports to Matroska for client delivery or final distribution
Social Media Managers
- Convert FLV videos to Matroska for compatibility with legacy players or archival systems that use Matroska
- Transform FLV source files to Matroska when a specific tool only accepts Matroska input
How to Convert FLV to Matroska
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1
Upload Your FLV File
Select or drag your Flash Video FLV into the upload area. Your file is transmitted securely using HTTPS encryption.
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2
Server-Side Conversion to MKV
FFmpeg remuxes or transcodes your FLV into the Matroska MKV container, preserving H.264 video and re-encoding audio to AAC for modern compatibility.
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3
Download Your MKV File
Your converted Matroska MKV downloads when ready. The original FLV is permanently deleted from our servers immediately after.
Developers: convert via API →
Frequently Asked Questions
MKV is a modern, open container format widely supported by VLC, Kodi, and all major media players. Converting FLV to MKV makes legacy Flash Video accessible on modern systems without Flash Player.
Yes. MKV's strong subtitle support means you can mux in SRT, ASS, or other subtitle formats using tools like MKVToolNix after converting from FLV.
If the FLV uses H.264, FFmpeg can often remux with minimal quality change. If transcoding is required (H.263, VP6 sources), some quality loss may occur.
FFmpeg supports MP3, AAC, and Nellymoser audio found in FLV files. All are converted to AAC in the MKV output for maximum compatibility.
MKV and FLV at the same codec and bitrate will have similar file sizes. The advantage of MKV is codec flexibility — you can use modern codecs like H.265 for better compression.
Up to 25MB per file (free tier; 100MB with eligible paid browser access). Trim larger FLV archives before uploading to ChangeThisFile.
Yes. Files are encrypted during upload and deleted immediately after conversion. No content is retained or analyzed.
VLC, MPC-HC, Kodi, PotPlayer, mpv, Windows 11's native player, and most modern media players support MKV natively.
Most FLV to MKV conversions complete within a minute. Processing time depends on file size and resolution.
Yes. ChangeThisFile is free with no accounts, subscriptions, or watermarks.
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Need to convert programmatically?
Use the ChangeThisFile API to convert FLV to Matroska in your app or script. Free tier included.
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