Modern CSS Feature Support For Shadow DOM

Feature List
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Last Updated: August 7, 2026

Changelog for: Has

August 7, 2026

Improvement

🎉 New milestone, ✔ 1 improvements

New milestone: 🎉 Feature is now Baseline widely available!

December 17, 2025

Began tracking feature

Support Definition Keys

Support Categories

Supported Per Spec
Acceptable Support
Use With Caution
Not Recommended

Functional Support Key

Unsupported: no support
Low: partial, insufficient support
Progressing: open issues/bugs for essential features
Critical: essential features for most expected use cases are supported
Supported: all expected features are supported

Shadow DOM Usage Key

Light DOM Priority: feature must be defined in the light DOM, but can be accessed in the shadow DOM
Cross-Context: feature can be defined and used within both light and shadow DOM
Cross-Boundary: feature can access light DOM definitions from within shadow DOM

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