MP4 to FLV Converter

AUTO-DELETE/Files are processed on our server and deleted as soon as conversion finishes.

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How to Convert MP4 to FLV Online

MP4 to FLV: what changes in the file

This tool takes a MP4 file, processes it with FFmpeg on DownloadVideo.vn servers and returns a FLV file.

Both MP4 and FLV are lossy, so converting adds another generation of compression: a small further loss that is usually hard to notice after one conversion.

How MP4 and FLV differ

Property	MP4	FLV
Full name	MPEG-4 Part 14	Flash Video
Introduced	ISO/IEC MPEG, 2003	Macromedia/Adobe, 2003
Compression	lossy	lossy
Common codecs	H.264, H.265/HEVC, AV1, AAC	Sorenson Spark, VP6, H.264, MP3, AAC
Strengths	plays on virtually every phone, browser, TV and editor; standard upload format for YouTube, TikTok, Facebook, Instagram	common in old video archives and early streaming downloads
Limitations	lossy codecs: every re-encode loses a little quality	Adobe Flash Player was retired in 2020 — browsers no longer play FLV; phones and modern TVs do not play it

Measured with a sample file

On September 25, 2026 we ran the tool on our production server with a sample file: a 10-second 1280×720 video (H.264 + AAC), 3.9 MB.

Result: 3.9 MB → 1.6 MB, processed in 3.4 s. Output: FLV1 video at 1280×720, MP3 audio at 44.1 kHz stereo, 128 kbps.

Real sizes depend on your content (how complex the picture and sound are, and the length); the figures only show the order of change.

Before you convert

The tool always re-encodes the picture and sound, even when the source codec would already fit the target format.
Up to 500 MB per file; a conversion that runs longer than 10 minutes is cancelled.
The file is sent to our server for conversion and deleted as soon as processing ends, including when it fails.

Frequently asked questions

Does converting MP4 to FLV reduce quality?

Slightly: it is a second round of lossy compression. One conversion is usually hard to notice, but repeated conversions add up.

How does the file size change from MP4 to FLV?

With our sample file: 3.9 MB → 1.6 MB. Your file may differ depending on its content.