Animation Loop Checker
Upload a clip meant to loop and this measures whether it actually does — and if it doesn't, whether a shorter window inside the clip loops better. Free, runs entirely in your browser — files never leave your machine.
Drop a video here or
MP4 / WebM / MOV · an idle, walk, or other repeating action works best
How it works
- Each frame's subject silhouette is extracted — keyed out on a plain backdrop if one is detected, otherwise estimated with a brightness threshold.
- The overlap (IoU) between the first and last frame's silhouette is measured, and compared against the average overlap between any two adjacent frames in the clip — that ratio is the "seam score".
- A seam score near 1.0 means the wrap-around jump is the same size as one ordinary step between frames — invisible. A low score means the last-to-first jump is much bigger than normal motion — a visible pop.
- The tool also searches for the best-scoring window inside the clip (skipping any frozen lead-in) and reports it if it beats the as-delivered seam.
- Both windows play side by side so you can compare the pop by eye, not just by number.
Why the seam score is normalized
A raw overlap number is meaningless on its own: 80% overlap between two frames is a great seam on a sprinting character and a terrible one on a slow idle breath, because a fast clip's frames simply differ more from each other to begin with. Dividing the seam's overlap by the clip's own average adjacent-frame overlap makes the number comparable across any clip's speed — a score of 1.0 always means "the loop is as smooth as the clip's own normal motion," regardless of how fast or slow that motion is.
Frequently asked questions
What counts as a "clean" loop?
A seam score of 0.85 or higher — meaning the jump from the last frame back to the first is no bigger than the clip’s own normal frame-to-frame motion. Below that, the wrap-around reads as a visible pop or snap.
What if my clip has no green screen?
The tool falls back to a brightness (luma) threshold to estimate the subject silhouette. This is a rougher signal than a proper key, so treat the numbers as approximate on non-keyed clips.
Why does it suggest a window shorter than my whole clip?
Many AI-generated clips open with a few frozen or near-static lead-in frames before the real motion starts. The tool skips that lead-in when searching for the best-looping window, since anchoring a loop inside a frozen stretch would score perfectly while showing nothing.
Does this fix or trim the video for me?
No — this is a measurement tool only, with no export. It tells you the window that loops best so you can re-cut the clip yourself, or run it through Sprite Studio, which can apply the recommended loop window as part of a confirmed export.
Is my video uploaded anywhere?
No. Decoding, masking and scoring all run in your browser. Your file never leaves your machine.