Why reversing is slower than it sounds
Video is stored forwards: most frames describe changes from the one before, so the last frame cannot be produced without decoding everything up to it. Reversing means decoding the whole clip, holding the frames, and writing them out in the opposite order.
That is memory-intensive. A long, high-resolution clip can exhaust a browser tab, which is why trimming to the section you actually want first is worth doing.
Reversed audio
Speech played backwards is unintelligible and unpleasant rather than interesting, so removing the audio is usually the better choice. Music and ambient sound reverse into something more listenable — the swelling attack of a reversed cymbal is a staple of film sound design.
Frequently asked questions
Why does it take so long?
Every frame has to be decoded before the last one can be written first — video is stored as changes from the previous frame. The whole clip is processed twice over.
Can I reverse a long video?
The limit is memory, since frames are held while the order is flipped. Trim to the section you want first.
Should I keep the audio?
Rarely, for speech — reversed voices are just noise. Music and ambience reverse into something genuinely usable.
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