CSS gains progress(), alpha() and revert-rule across all engines

In September 2026 Chrome 153–154, Firefox 155–157 and Safari 27 reached stable, making several CSS features Baseline Newly available: progress(), alpha(), revert-rule, font-width, scroll anchoring and image values in light-dark().

• alpha() sets opacity from a single source color, removing duplicate custom properties
• progress() returns a number between a start and end value, replacing media query ladders
• revert-rule rolls a property back as if the current rule did not exist
• Safari 27 enabled scroll anchoring and added overflow-anchor