MP4 to FLV Converter
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Supports: MP4, M4V
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Need help?How to Convert MP4 to FLV
- Upload Your MP4 File — Click "Choose Files" or drag and drop your MP4 or M4V video file. Both extensions are accepted.
- Choose Video Codec — Under Video Codec, the default for FLV output is FLV (Flash Video).
- Set Video Quality — Under File Compression, choose from: Quality Preset (Highest through Lowest), Target File Size % (1-100% slider with Smart Scaling), Specific File Size (MB/KB), Constant Bitrate, Variable Bitrate, Constant Quality (CRF), or Constraint Quality.
- Set Audio Codec — Under Audio Codec, the default for FLV is AAC.
- Adjust Resolution (Optional) — Under Video Resolution, keep the original or choose Preset Resolutions (1080p, 720p, 480p, etc.), Fixed Resolutions, Resolution Percentage, or custom Width/Height/Width×Height.
- Trim (Optional) — Under Trim, set a Start Time and Duration to extract a specific segment.
- Convert & Download — Click "Convert" and download your FLV file.
Why Convert MP4 to FLV?
FLV (Flash Video) was the standard format for web video streaming before HTML5. While Adobe discontinued Flash Player in 2020, FLV is still needed for RTMP streaming servers that require FLV input (OBS, Wowza, nginx-rtmp), legacy content management systems that only accept FLV uploads, maintaining compatibility with Flash-based kiosks and digital signage, and archival workflows that store video in FLV format.
MP4 vs FLV Comparison
| Feature | MP4 | FLV (Flash Video) |
|---|---|---|
| Video codec | H.264 (typical) | FLV (default) |
| Audio codec | AAC (typical) | AAC (default) |
| Container | MPEG-4 Part 14 | Flash Video |
| Browser support | Universal (HTML5) | None (Flash discontinued) |
| Streaming | HLS, DASH | RTMP |
| File size | Efficient | Comparable |
| Best for | Modern playback | RTMP streaming, legacy systems |
RTMP Streaming Use Case
FLV is the native format for RTMP (Real-Time Messaging Protocol) streaming. Many live streaming setups still use RTMP for ingest:
- OBS Studio → RTMP server → CDN
- Wowza Streaming Engine — accepts FLV/RTMP input
- nginx-rtmp module — requires FLV format
- Legacy Flash media servers — FLV is the only accepted format
Why would I convert to FLV in 2026?
The main use case is RTMP streaming infrastructure. Many live streaming platforms still accept RTMP ingest (which uses FLV internally), even though viewers receive the stream as HLS/MP4. Legacy kiosks, digital signage, and content management systems may also require FLV.
What is the FLV codec?
The default FLV codec is Sorenson H.263 (Flash Video). You can change to H.264 under Video Codec for better quality — H.264 in FLV containers is supported by most RTMP servers and VLC.
Will the file size change?
FLV with the default FLV codec produces comparable file sizes to MP4 with H.264. If you switch to H.264 codec within the FLV container, file sizes will be similar to the original MP4.
Can modern browsers play FLV files?
No — all major browsers removed Flash support in 2020-2021. FLV files can be played in VLC, MPC-HC, and standalone Flash Player. For web playback, keep your video as MP4.
Can I trim the video during conversion?
Yes. Under Trim, select "Time Range" and enter a Start Time and Duration in seconds or HH:MM:SS.sss format. This extracts only the specified segment.