Convert Matroska Video (.mkv) to Flash Video (.flv) online for free. Fast, secure video conversion with no watermarks or registration.
Conversion settings — add a file to adjust
Upload your .mkv file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .flv file when it's ready.
FLV (Flash Video) was the dominant web video format throughout the 2000s, powering early YouTube, Newgrounds, and countless Flash-based video players. While Flash is officially dead, FLV conversion remains necessary for maintaining legacy web applications, archival projects, and certain RTMP streaming workflows that still use FLV as their transport container.
RTMP live streaming, which underpins services like Twitch, YouTube Live, and Facebook Live, uses FLV as its container format at the transport layer. If you have pre-recorded MKV files that need to be pushed through an RTMP server (Nginx-RTMP, Wowza, or OBS Studio's media source), converting to FLV with H.264 video and AAC audio ensures seamless ingestion without container mismatch errors.
Additionally, some legacy content management systems, e-learning platforms built in the Flash era, and archival collections still reference FLV files. Media preservation projects occasionally need to convert modern MKV recordings back to FLV to match the original format of materials being archived, ensuring bit-exact container consistency within a collection.
FFmpeg transcodes the MKV to FLV using H.264 (Constrained Baseline profile for Flash compatibility) with AAC-LC audio. The FLV container supports H.264, VP6, and Sorenson Spark for video, plus AAC, MP3, Speex, and ADPCM for audio. Resolution is typically preserved from the source, though older Flash players may struggle with resolutions above 720p. The moov atom concept does not apply to FLV since it uses a different metadata structure with a header and tag-based layout.
Video quality depends on the chosen H.264 encoding parameters. At CRF 20-23, the output is visually indistinguishable from the MKV source at the same resolution. FLV does not impose inherent quality limitations — it is simply a container. The same H.264 bitstream in FLV and MP4 would look identical. AAC audio at 128 kbps provides transparent quality for most applications.
| Device | MKV | FLV |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Partial | Partial |
| Linux | Partial | Partial |
| Web Browser | No |
Resolution: 1920x1080
Bitrate: 8-12 Mbps
H.264 recommended for fast processing
Resolution: 1080x1080
Bitrate: 3.5 Mbps
Square or 9:16 for Reels
Resolution: 1080x1920
Bitrate: 4 Mbps
9:16 vertical, under 60s ideal
Resolution: 1280x720
Bitrate: 5 Mbps
Under 140s, 512MB max
Resolution: 960x540
Bitrate: 2 Mbps
16MB limit for standard, 64MB for document
Resolution: 1280x720
Bitrate: 4 Mbps
MKV to FLV conversion is a niche but essential workflow for RTMP streaming, Flash-era system maintenance, and media archival consistency.
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| Funktion | MKV | FLV |
|---|---|---|
| Fulde navn | Matroska Video | Flash Video |
| Filendelse | .mkv | .flv |
| Bedst til | Multiple audio tracks | Small file size |