Supported formats and limits, and how to convert a video that does not fit

Updated October 26, 2026 · Peelframe

If a video will not open, or you see a message that it exceeds the size or length that can be processed, the cause is almost always its format or size. Here is what Peelframe accepts and how to convert a video that does not fit, using free tools.

What is supported

Codecs the browser cannot read directly go through a compatibility path, which is slower. Videos with rotation information are saved upright, and videos with uneven frame timing (common in phone footage) are saved at their average frame rate.

Tools

Everything below can be done with free tools.

• HandBrake — a free, open-source converter with a graphical interface (Windows, macOS, Linux).
• ffmpeg — a free, open-source command-line tool. Copy the commands below and change only the file names.

Downscaling 4K and other large videos

In HandBrake, open the video, choose a 1080p preset and check on the Dimensions tab that the long side is 1920 px or less before saving. With ffmpeg:

Landscape: ffmpeg -i input.mp4 -vf "scale=1920:-2" -c:v libx264 -crf 18 -preset medium -c:a copy output.mp4
Portrait:  ffmpeg -i input.mp4 -vf "scale=-2:1920" -c:v libx264 -crf 18 -preset medium -c:a copy output.mp4

-2 keeps the aspect ratio and rounds to an even size; -crf 18 is high quality, visually close to the source.

Splitting videos longer than 3 minutes

ffmpeg -i input.mp4 -c copy -map 0 -f segment -segment_time 170 -reset_timestamps 1 part_%02d.mp4

This splits into pieces of about 170 seconds without re-encoding. Cuts can only fall on keyframes, so pieces may run a little longer than asked, which is why it leaves a margin below 3 minutes (180 s). Process each piece, then join them in order in an editor.

Shrinking files over 120 MB

If the resolution and length are fine but the file is too big (footage from high-bitrate cameras or phones), re-encode it:

ffmpeg -i input.mov -c:v libx264 -crf 20 -preset medium -c:a aac -b:a 160k output.mp4

A higher -crf gives a smaller file and lower quality; pick between 18 and 23. In HandBrake, the Constant Quality value on the Video tab does the same.

Videos that will not open

• “This browser cannot read this video format” — convert it to MP4 (H.264): ffmpeg -i input.mkv -c:v libx264 -crf 18 -c:a aac output.mp4
• “A damaged part was found in the video file” — the file is incomplete or corrupted. Download the original again or re-save it with another program.
• Older formats such as AVI, WMV and FLV are not on the list. Convert them to MP4 first.

Losing as little quality as possible

Convert once, at high quality (around -crf 18). Every round of compression costs detail, and areas the AI has redrawn soften first. For settings that take uploading into account, see keeping quality when you upload.