2027 Web Platform Feature Ranking

Ranked proposals (top = most important)

1. CSS interpolate-⁠size property and calc-⁠size() function

   Allows animating to height: auto, and using intrinsic sizes in calculations.
2. Allow CSS transitioning/animating display and content-⁠visibility

   Useful for delaying display: none until an exit animation completes.
3. HTML focusgroup attribute

   Combines descendant elements into a single tab stop, with arrow-key navigation between them.
4. CSS flex-⁠wrap: balance

   Distributes items in a multi-line flex container so each line has about the same number of items.
5. CSS margin-⁠trim

   Removes the margins of child elements when they meet the edges of the container.
6. CSS gap decorations

   column-⁠rule and row-⁠rule display decorative lines between columns and rows of a flex, grid, or multi-column layout.
7. CSS color gamut mapping

   Displays out-of-gamut colors (such as from oklch()) closer to the intended color, rather than clipping RGB channels.
8. JavaScript Temporal

   A modern and extensive date/time API to replace Date.
9. CSS reading-⁠flow and reading-⁠order properties

   Sets the order in which flex or grid elements are rendered to speech or reached via focus navigation.
10. HTML headingoffset and headingreset attributes

    Offsets the heading level of descendant <h1>–<h6> elements. Includes the CSS :heading() pseudo-class.
11. CSS anchor positioning with transforms and animations

    Anchor-positioned elements track transforms on their anchors, and changes to the calculated anchor() triggers transitions.
12. CSS grid lanes (masonry)

    display: grid-⁠lanes creates a layout where items are tightly packed into parallel lanes.
13. CSS border-⁠shape property

    Sets the geometry of the border box to a fully custom shape, changing the shape of borders, outlines, and shadows.
14. CSS @function

    Defines custom functions that take arguments and return a CSS value.
15. Progressive rendering of JPEG XL and AVIF images

    Displays a preview version of the image while the rest downloads.