Define support targets before rolling Keel across multiple sites.

Tier policy

• Tier 1 (fully supported): latest two stable versions.
• Tier 2 (best effort): third most recent version.
• Unsupported: legacy browsers without CSS variable support.

Matrix

Browser	Tier	Notes
Chrome (desktop)	Tier 1	Primary QA baseline
Edge (desktop)	Tier 1	Chromium parity expected
Firefox (desktop)	Tier 1	Validate color-mix and focus visuals
Safari (macOS)	Tier 1	Validate typography and sticky layouts
iOS Safari	Tier 1	Verify forms, drawers, sticky topbar
Chrome Android	Tier 1	Verify responsive dashboard layouts
Samsung Internet	Tier 2	Best effort for consumer traffic

Feature assumptions

Keel requires support for:

• CSS custom properties
• light-dark()
• color-mix()
• :focus-visible

If a target browser misses these features, add fallbacks at app layer before rollout.