When @keyframes rules are used to animate elements and the 'from' selector is missing, the animation behaves erratically. See this example: https://stackblitz.com/edit/web-platform-vmalvc?file=styles.css styles.css contains this @keyframes rule: @keyframes dash { to { stroke-dashoffset: 0; } } Running the project in Safari Technology Preview, I find that the line is animated erratically: anywhere from 20-60% of the time. If I add the 'from' keyword: @keyframes dash { from { stroke-dashoffset: 14.7; } to { stroke-dashoffset: 0; } } The animation seems to happen consistently. W3C says that 'If a 0% or from keyframe is not specified, then the user agent constructs a 0% keyframe using the computed values of the properties being animated.' That computation does not seem to be happening consistently. (Other browsers like Chrome work fine.) (Reference: https://www.w3.org/TR/css-animations-1/)
<rdar://problem/84903751>
Can you still reproduce the issue with Safari Technology Preview 139? I'm not able to reproduce it myself.
Verified: no longer reproduces.
Great! Thanks for checking.