FLV MP4

FLV to MP4 Converter

Convert FLV to MP4 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 FLV 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 FLV to MP4?

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

Common use cases

  • You have a FLV file and need it in MP4 format.
  • The target software or platform requires MP4 but your file is in FLV.
  • Typical use of MP4: Video for YouTube, social media, and streaming services.
  • You want to reduce file size or improve compatibility without using desktop software.
Keep in mind: MP4 with H.264 is widely supported but not fully open — H.264 is patent-encumbered, and H.265 has even more complex licensing.

How to Convert FLV to MP4

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

About the Formats

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.

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.

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?

MP4 to FLV 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.