MP4 FLV

MP4 to FLV Converter

Convert MP4 to FLV in your browser. Free, private, and fast. Tune codec, quality, and compatibility without sending files to a server.

This converter runs a full FFmpeg engine in your browser. The first conversion downloads the engine (~31 MB, cached afterwards) — your file itself still never leaves your device.

Drag & drop your MP4 file here

or

Max file size: 50 MB · Your file stays in your browser

Your file is processed locally in your browser — nothing is ever uploaded.

Why Convert MP4 to FLV?

Converting MP4 to FLV is a common task whenever a file has to work somewhere that expects the other format. MP4 is the world's most widely supported video container format. FLV is the Flash Video container that powered online video in the era of Adobe Flash Player. This converter makes the switch locally in your browser — nothing is uploaded.

Common use cases

  • You have a MP4 file and need it in FLV format.
  • The target software or platform requires FLV but your file is in MP4.
  • Typical use of FLV: Rescuing old Flash-era videos so they play on modern devices.
  • You want to reduce file size or improve compatibility without using desktop software.
Keep in mind: Flash was discontinued in 2020 and no browser plays FLV any more. Convert to MP4 or WebM for everyday use.

How to Convert MP4 to FLV

  1. Upload or drop your MP4 file into the converter above.
  2. Adjust any output settings for FLV if needed.
  3. Click Convert and download your converted file instantly.

About the Formats

MP4 (MPEG-4 Part 14)

MP4 is the world's most widely supported video container format. It efficiently stores video (H.264 or H.265), audio, and subtitles in a single file with excellent compression.

Compatibility: Universal — supported by every browser, device, operating system, and video platform.

FLV (Flash Video)

FLV is the Flash Video container that powered online video in the era of Adobe Flash Player. Many old web video downloads, screen recordings and streaming archives still use it.

Compatibility: VLC and other ffmpeg-based players. No browser support since the end of Flash.

100% Private & Browser-Based

Your files never leave your device. All conversion happens locally in your browser — nothing is uploaded to any server. No sign-up required.

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Need the reverse?

FLV to MP4 Converter

FAQ

Frequently Asked Questions

Yes — completely free with no sign-up, no watermarks, and no size limits for typical files.

Quality depends on the output settings. For lossless output, choose the highest quality setting available.

Your file is processed entirely within your browser using local JavaScript. It is never uploaded to any server. Only you can access your file.

For browser-based conversion, files up to 50 MB work best. Very large files may take longer depending on your device. We recommend splitting very large files before converting.

Currently, AintoB converts one file at a time to keep the browser-based process simple and private. Reload the page to convert another file.