Can I convert several at once?

Yes: in HandBrake add them to the queue; with FFmpeg, use a small loop in the terminal.

Does Dembed accept AVI directly?

For it to play in every browser, upload it already converted to MP4 (H.264 + AAC).

How to convert AVI, WMV or FLV to MP4 for free

Updated: November 10, 2026

AVI, WMV and FLV are formats from another era: old cameras, Windows Movie Maker, videos downloaded from Flash sites. Modern browsers don’t play them, so before uploading or sharing them you need to convert them to MP4.

With HandBrake (free, Windows, Mac and Linux)

1Install HandBrake from its official site and open your video.
2Choose the “Fast 1080p30” preset (or “Fast 720p30” if the original is small).
3Check that the format is MP4 and the video codec H.264.
4Click “Start” and wait for it to finish.

With VLC (if you already have it)

1Media → Convert/Save → Add your file → Convert/Save.
2Under Profile, choose “Video - H.264 + MP3 (MP4)” or “H.264 + AAC” if available.
3Choose where to save the file with a .mp4 extension and click Start.

With FFmpeg (one line, the fastest)

Swap “video.avi” for your .wmv or .flv file: the command is the same. “-movflags +faststart” makes the video start playing sooner on the web.

ffmpeg -i video.avi -c:v libx264 -crf 22 -preset medium -c:a aac -b:a 160k -movflags +faststart video.mp4

Tips for old videos

Don’t upscale: a 480p video gains no detail by exporting it at 1080p.
If the video is interlaced (lines on movement), enable the “Deinterlace” filter in HandBrake.
Check the sound in the converted file before deleting the original.

Frequently asked questions

A little, since it’s compressed again, but with a CRF of 20–22 you won’t notice.