Convert FLV to MP4
Convert FLV (Flash Video) files to MP4 directly in your browser. FLV is a dead format that no modern player or platform supports — converting to MP4 with H.264 makes your old Flash video archives playable everywhere again. No upload needed.
Drag 'n' drop files here, or
click to select files
.flv, .f4v
Drop your files and click Convert to get MP4
//when_to_use
When to Convert FLV to MP4
- Converting old YouTube FLV downloads from the Flash era to MP4 for playback on modern phones and tablets
- Rescuing FLV screencasts recorded with Camtasia or Adobe Captivate to MP4 for upload to current platforms
- Migrating FLV training videos from a legacy LMS to MP4 for embedding in modern learning systems
- Converting FLV webinar recordings to MP4 for sharing on Zoom, Teams, or Google Drive
- Archiving FLV video collections as MP4 to ensure long-term playability after Flash discontinuation
//comparison
FLV vs MP4
| Property | FLV | MP4 |
|---|---|---|
| Container | FLV (Flash, EOL 2020) | MP4 (ISO/IEC 14496-14) |
| Video codec | H.263, VP6, H.264 | H.264 (CRF 23) |
| Audio codec | MP3, AAC, Nellymoser | AAC 128kbps |
| Modern player support | None (Flash dead) | Universal |
| Mobile playback | No | iOS, Android native |
| Best for | Legacy Flash archive | Modern playback, sharing |
//how_it_works
How It Works
Drop your FLV files
Drag and drop or select FLV or F4V files. First use loads FFmpeg WASM (~30MB).
FFmpeg decodes FLV
FFmpeg WASM parses the FLV container and decodes the video (Sorenson, VP6, or H.264) and audio (MP3 or AAC) streams to raw frames and PCM.
H.264 + AAC re-encode
Video is re-encoded to H.264 at CRF 23 with libx264 medium preset; audio is re-encoded to AAC at 128kbps. Output is wrapped in an MP4 container.
Download your MP4 files
Your MP4s play in QuickTime, VLC, mobile devices, browsers, and every modern video editor.
// under the hood
FLV is the Flash Video container format, typically holding Sorenson Spark (H.263), VP6, or H.264 video with MP3 or AAC audio. Our converter uses FFmpeg WASM to demux the FLV container, decode the video stream, and re-encode to H.264 at CRF 23 using libx264 with the medium preset. Audio is re-encoded to AAC at 128kbps. The result is wrapped in an MP4 container with the moov atom at the start for fast streaming.
//faq
Frequently Asked Questions
- Why convert FLV to MP4?
- FLV (Flash Video) was discontinued when Adobe killed Flash in 2020. No modern browser, mobile player, or streaming platform supports FLV. Converting to MP4 with H.264 video and AAC audio gives you a file that plays in QuickTime, VLC, mobile devices, social platforms, and every modern video editor.
- Will the video quality stay the same?
- Most FLV files use H.263 or VP6 video. We re-encode to H.264 at CRF 23 — visually transparent for most content. There's a small quality cost from re-encoding, but the result is dramatically more compatible than the original FLV. If your FLV is H.264 inside (some are), the re-encode is unavoidable in the browser but uses sensible defaults.
- What about the audio?
- FLV typically holds MP3 or AAC audio. We re-encode to AAC at 128kbps in the MP4 container, which is the standard for MP4 distribution. Audio quality is preserved at near-transparent levels.
- Are very large FLV files supported?
- Browser memory is the limit — FFmpeg WASM has a 2GB working memory cap. For typical FLV files (recorded screencasts, web video archives) under ~1GB this works fine. If you have multi-gigabyte FLV files, our desktop app handles them without limits.
- Are my files uploaded?
- No. FFmpeg WebAssembly runs entirely in your browser. Your FLV files never leave your device.
//related_converters
Related Converters
Similar conversions you might need.
Convert MOV to MP4
Convert iPhone MOV videos to universally compatible MP4 format.
→Convert WebM to MP4
Convert WebM videos to universally compatible MP4 format.
→Convert AVI to MP4
Convert legacy AVI videos to modern MP4 format for any device.
→Convert MKV to MP4
Convert MKV videos to universally compatible MP4 format.
→Convert OGV to MP4
Convert OGV (Ogg Theora) video files to modern MP4 H.264 format.
→Convert MP4 to MP3
Extract audio from MP4 videos and save as MP3 files.
→