MP4 to FLV Converter

Inspect your MP4 file details in the browser and get clear instructions for converting it to FLV with free desktop tools — no upload required.

MP4 File Inspector

MP4 vs FLV — Format Comparison

Property MP4 FLV
Full name MPEG-4 Part 14 Flash Video
Container ISOBMFF (.mp4) Adobe FLV (.flv)
Video codecs H.264, H.265, AV1 H.263, H.264, VP6
Audio codecs AAC, MP3, Opus AAC, MP3
Browser support All modern browsers Requires Flash (deprecated)
Streaming HLS, DASH, progressive RTMP (legacy)
File extension .mp4 / .m4v .flv

How to Convert MP4 to FLV

1

FFmpeg (recommended — free & open source)

Install FFmpeg from ffmpeg.org, then run this command in your terminal: 

ffmpeg -i input.mp4 -c:v libx264 -c:a aac output.flv
2

HandBrake (free GUI app)

  1. Download HandBrake from handbrake.fr and open it.
  2. Click Open Source and select your MP4 file.
  3. In the Format dropdown choose MKV File, then manually rename the output extension to .flv after export (HandBrake does not have a native FLV preset).
  4. For true FLV output, use the FFmpeg command above — HandBrake is better for MP4/MKV targets.
3

VLC Media Player (quick one-off)

  1. Open VLC and go to Media > Convert / Save.
  2. Click Add, select your MP4 file, then click Convert / Save.
  3. In the Profile dropdown, choose Video — H.264 + MP3 (MP4) as a base.
  4. Click the wrench icon, open the Encapsulation tab and select FLV.
  5. Set the destination file name with a .flv extension and click Start.

FLV is a legacy format. For new projects, consider staying with MP4 or WebM — they play natively in all modern browsers and streaming platforms without additional plugins.

Summary

Inspect your MP4 file details in the browser and get clear instructions for converting it to FLV with free desktop tools — no upload required.

How it works

  1. Click "Choose MP4 File" to select a local .mp4 video — the file never leaves your device.
  2. The tool reads metadata (name, size, type, duration) directly from the File API in your browser.
  3. Review the format comparison table to understand key differences between MP4 and FLV.
  4. Pick a desktop conversion method — FFmpeg CLI, HandBrake, or VLC — and follow the provided command or steps.
  5. Run the conversion locally on your machine to produce the FLV file.

Use cases

  • Prepare video clips for legacy Flash-based players or websites.
  • Re-encode content for older streaming servers that require FLV.
  • Archive video in FLV format for compatibility with older editing tools.
  • Understand the technical differences between MP4 and FLV before converting.
  • Quickly check an MP4 file size and type without uploading it anywhere.
  • Find the correct FFmpeg command for MP4-to-FLV transcoding.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu