Convert MP4 to FLV — Free Online Converter
Convert MPEG-4 Part 14 (.mp4) to Flash Video (.flv) online for free. Fast, secure video conversion with no watermarks or registration....
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Upload your .mp4 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.
About MP4 to FLV Conversion
MP4 to FLV conversion repackages your MPEG-4 video into the Flash Video container format. FLV was the dominant streaming format of the mid-2000s, powering the original YouTube, Newgrounds, and countless Flash-based video players. While Adobe officially discontinued Flash Player in December 2020, FLV remains relevant for legacy content management systems, RTMP live-streaming workflows, and archival of era-specific web content.
Our converter uses FFmpeg to transcode MP4 video to the Sorenson Spark (H.263) or VP6 codec and audio to MP3 or ADPCM within the FLV container. Alternatively, H.264 video can be muxed into FLV directly for RTMP-compatible output.
Why Convert MP4 to FLV?
The primary modern use case for FLV is RTMP (Real-Time Messaging Protocol) streaming. Many live-streaming servers including Wowza, Nginx-RTMP, and some CDN ingest points expect FLV-wrapped H.264 streams. OBS Studio and similar broadcasting software output FLV for RTMP delivery. Additionally, organizations with legacy CMS platforms built during the Flash era may still require FLV files for their video libraries until they complete their migration to HTML5.
Common Use Cases
- Prepare H.264 video wrapped in FLV for RTMP live-streaming server ingest
- Upload video to legacy content management systems that only accept FLV
- Archive web content from the Flash era in its original distribution format
- Feed video to older digital signage systems built around Flash-based players
- Create FLV assets for historical preservation of early web video culture
How It Works
For RTMP use, the converter muxes H.264 video and AAC audio directly into the FLV container without re-encoding, since FLV supports these codecs natively. For legacy Flash Player compatibility, video is transcoded to Sorenson Spark at up to 720p with MP3 audio. FLV uses a simple tag-based structure with interleaved audio and video tags, each timestamped for synchronization. The onMetaData tag stores duration, dimensions, bitrate, and codec information.
Quality & Performance
When using H.264 inside FLV (for RTMP), quality is identical to the source MP4 since it is a container change only. When transcoding to Sorenson Spark for legacy compatibility, quality degrades significantly — the codec is far less efficient than H.264, producing softer images with more blocking artifacts at equivalent bitrates.
Device Compatibility
| Device | MP4 | FLV |
|---|---|---|
| Windows PC | Native | Partial |
| macOS | Native | Partial |
| iPhone/iPad | Native | Partial |
| Android | Native | Partial |
| Linux | Partial | Partial |
| Web Browser | Native | No |
Recommended Settings by Platform
YouTube
Resolution: 1920x1080
Bitrate: 8-12 Mbps
H.264 recommended for fast processing
Resolution: 1080x1080
Bitrate: 3.5 Mbps
Square or 9:16 for Reels
TikTok
Resolution: 1080x1920
Bitrate: 4 Mbps
9:16 vertical, under 60s ideal
Twitter/X
Resolution: 1280x720
Bitrate: 5 Mbps
Under 140s, 512MB max
Resolution: 960x540
Bitrate: 2 Mbps
16MB limit for standard, 64MB for document
Discord
Resolution: 1280x720
Bitrate: 4 Mbps
8MB free, 50MB Nitro
Tips for Best Results
- 1Use H.264 + AAC inside FLV for RTMP streaming — no re-encoding needed
- 2Only transcode to Sorenson Spark if the target system genuinely requires legacy Flash codecs
- 3Set the onMetaData tag correctly — many FLV players depend on it for seeking
- 4For live streaming, ensure keyframe interval is 2 seconds for smooth RTMP delivery
- 5Consider migrating FLV archives to MP4 rather than creating new FLV content
Related Conversions
MP4 to FLV serves two audiences: RTMP live-streamers who need FLV-wrapped H.264, and organizations maintaining legacy Flash-era systems. For modern web playback, MP4 with H.264 is always the better choice.