The interpolate-size property controls whether intrinsic-size keywords (auto, fit-content, max-content) can interpolate with lengths during animation. Previously impossible; allow-keywords enables smooth animations from auto to a numeric value.:root {
interpolate-size: allow-keywords;
}details {
interpolate-size: allow-keywords;
transition: height 300ms ease;
}numeric-onlyIntrinsic-size keywords cannot interpolate (default for compatibility).allow-keywordsInterpolation allowed between auto/fit-content/max-content/min-content and lengths — enables smooth animations.CSS Values and Units Module Level 5Editor's DraftW3CMDN
