How to reverse a video
1. Drop one video. Audio files and pictures are refused. 2. If the clip is longer than 15 seconds, cut it with Trim video first. 3. Press “Reverse video” and play the download from the start: that frame used to be the end.
A video with a soundtrack comes back with the soundtrack reversed too. A silent video stays silent.
Why long clips are refused
Reversing stores every frame in this tab, so a long video is refused instead of freezing the browser. Clips whose long side is over 640 px are scaled down before the reverse. A clip that already fits is not enlarged.
The cap is what a single browser thread can hold, not a paid limit. Trim video makes a shorter file you can reverse.
The file stays in this tab
The first visit downloads FFmpeg. After that the browser cache is enough and you can disconnect. GustKit does not keep the video.
How to tell the reverse worked
1. Play the first second of the download. It should be the old ending. 2. Play the last second. It should be the old opening. 3. If the clip was too long, trim it under the limit shown on the page and run again.
Picture and sound reverse together. A clip that is already small is not enlarged. A long side over the cap is scaled down so the browser can hold the frames. Nothing is uploaded.