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The box outline is one line that unspools: its tail runs off the top and around the box while its head flows into the tick, so the box becomes the check. A tint fills in behind.
Also known as: outline to checkmark animation, box turns into tick css, one line checkbox animation, svg path morph checkbox.
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Everything you see above is live. Basic and Pro include every premium piece, with the HTML and CSS ready to copy, plus the Tailwind version where there is one and Motions in Claude Code on Pro.
--chk-color on the element or a parent.
Currently previewing #3b82f6.--chk-size. Every other dimension is in
em, so the whole thing scales together. Currently previewing 24px.transition or animation
shorthand. Staggered delays are relative, so they keep their rhythm.