FLV to MP4 Converter
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Convert FLV to MP4 online
Convert FLV to MP4 to open a file from the Flash era. FLV was built for a browser plugin that no longer exists, so these files are usually old downloads or archives that nothing modern will play.
When should you convert FLV to MP4?
- Recover video from an archive of old web downloads
- Play a Flash-era recording on current hardware
- Re-upload legacy content to a modern platform
- Edit old footage in software that will not import FLV
Before you convert
Source quality sets the ceiling
FLV files are usually low-resolution and heavily compressed. H.264 will encode them efficiently but cannot add detail that was never there.
Nothing plays FLV any more
Flash was discontinued in 2020. If you have FLV files worth keeping, converting them now is worth doing before the tooling disappears too.
What happens to your file
FLV to MP4 is a full re-encode, not a container swap: the video is decoded and re-compressed with libx264 (H.264) at CRF 23, preset medium, and the audio is re-encoded to AAC at 192 kbps. The MP4 index is moved to the front of the file (+faststart) so it can start playing before the whole download finishes, and pixels are written as yuv420p for maximum device compatibility.
Settings this conversion runs with
| Engine | ffmpeg |
|---|---|
| Video codec | libx264 (H.264) |
| Video quality | CRF 23, preset medium |
| Audio codec | AAC |
| Audio bitrate | 192 kbps |
What changes
- The FLV picture is decoded and re-compressed with libx264 (H.264), so this is a generation loss: the output is built from an already-compressed source, not from the original camera data. Converting FLV to MP4 and back will soften the clip a little more each time.
- Only one video and one audio stream reach the MP4 file. Additional audio languages, embedded subtitle tracks, and chapter markers are not carried across.
About FLV and MP4 files
FLV video
Strengths
- good for moving images
Limitations
- compatibility varies by device
MP4 video
Strengths
- plays almost everywhere
- good quality-to-size
- widely supported
Limitations
- lossy compression
- less flexible than MKV
FLV vs MP4
| Format | FLV | MP4 |
|---|---|---|
| Compression | — | Lossy |
| Transparency | — | — |
| Best for | playback, streaming | streaming and sharing, playback on any device |
Related tools
Frequently asked questions
- Does converting FLV to MP4 re-encode the file?
- FLV to MP4 is a full re-encode, not a container swap: the video is decoded and re-compressed with libx264 (H.264) at CRF 23, preset medium, and the audio is re-encoded to AAC at 192 kbps. The MP4 index is moved to the front of the file (+faststart) so it can start playing before the whole download finishes, and pixels are written as yuv420p for maximum device compatibility.
- What should you know before converting FLV to MP4?
- The FLV picture is decoded and re-compressed with libx264 (H.264), so this is a generation loss: the output is built from an already-compressed source, not from the original camera data. Converting FLV to MP4 and back will soften the clip a little more each time.
- Is this FLV to MP4 converter free?
- Yes. You can convert FLV to MP4 online for free, with no account and no watermark.
- Do I need to install software or sign up?
- No. Use the converter from your browser without installing software or creating an account. Files are uploaded to our servers for processing.
- Will converting FLV to MP4 reduce quality?
- MP4 uses lossy compression, so the file can get smaller while some visual quality may change.
- Are my files safe?
- Yes. Files are processed only to complete the conversion and are auto-deleted after 2 hours. We never share them.