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HTML/CSSIntermediate#html#semantics
HTML/CSSAdvanced#css#performance
How does the 'will-change' property affect rendering performance?
will-change hints to the browser that a property (like transform or opacity) will change soon, letting it optimize ahead of time (e.g., promoting the element to its own compositor layer). Overusing it on many elements wastes memory and can hurt performance, so apply it sparingly and only right before the change happens.
Example
.card { will-change: transform; }
.card:hover { transform: scale(1.05); }
/* Better: add via JS just before animating, remove after */