diff --git a/sites/website/src/docs/3.x/resources/browser-support.md b/sites/website/src/docs/3.x/resources/browser-support.md
index 427583d08a8..c84ae616020 100644
--- a/sites/website/src/docs/3.x/resources/browser-support.md
+++ b/sites/website/src/docs/3.x/resources/browser-support.md
@@ -8,12 +8,21 @@ eleventyNavigation:
   title: Browser Support
 navigationOptions:
   activeKey: browser-support3x
-description: View the list of browsers that have native support for the Web Components features and native globalThis required by fast-element v3.
+description: View browser and application support guidance for FAST Element v3 features, fallbacks, and optional SSR/hydration capabilities.
 keywords:
   - browser support
 ---
 
-The following browsers have native support for the Web Components features used by `@microsoft/fast-element`, including the native `globalThis` required by v3:
+FAST Element v3 builds on native web platform features. The baseline
+client-rendered runtime expects autonomous custom elements, Shadow DOM, and
+native `globalThis` support. Optional capabilities, such as Declarative Shadow
+DOM hydration and constructable stylesheets, use newer browser features when
+they are available.
+
+## Baseline runtime support
+
+The following browser versions have native support for the baseline features used
+by client-rendered `@microsoft/fast-element` components:
 
 * Microsoft Edge 79+
 * Mozilla Firefox 65+
@@ -27,6 +36,33 @@ The following browsers have native support for the Web Components features used
 * Firefox for Android 68+
 * Samsung Internet 10.0+
 
-FAST Element v3 no longer polyfills `globalThis` for older engines. If you need
-to support an environment below these minimums, load a `globalThis` polyfill
-before importing FAST.
+FAST Element v3 does not include platform polyfills. If an application must run
+below these minimums, load standards-compatible polyfills before importing FAST.
+
+## Feature support matrix
+
+| Feature | Browser support guidance | Fallback and application requirements |
+|---|---|---|
+| Web Components / custom elements | Supported by the baseline browsers above for autonomous custom elements. FAST Element does not use customized built-in elements. | No FAST fallback. Browsers must provide native custom elements, or the application must load compatible platform polyfills before defining FAST elements. |
+| Shadow DOM | Supported by the baseline browsers above. FAST creates an open shadow root by default for templates and style encapsulation. | No FAST Shadow DOM polyfill. Components that intentionally set `shadowOptions: null` can render to light DOM, but default FAST Element authoring expects browser Shadow DOM support. |
+| Declarative Shadow DOM | Optional for client-only rendering. Hydration requires browser support for `<template shadowrootmode>`, such as Chrome/Edge 111+, Firefox 123+, Safari/iOS Safari 16.4+, Opera 97+, Samsung Internet 22+, and current Chromium-based mobile browsers. | FAST hydrates an existing shadow root; it does not make unsupported browsers parse Declarative Shadow DOM. Older browsers need an application-level DSD transform/polyfill before components connect, or they should use client rendering. |
+| `adoptedStyleSheets` / constructable stylesheets | Supported in Chrome 73+, Edge 79+, Firefox 101+, Safari/iOS Safari 16.4+, Opera 60+, Samsung Internet 11.1+, and current Chromium-based mobile browsers. | FAST falls back to injected `<style>` elements for string-based `css` styles when adopted stylesheets are unavailable. Passing `CSSStyleSheet` instances directly requires browser constructable stylesheet support. |
+| Trusted Types | Not part of the FAST Element baseline. Available in Chromium-based browsers such as Chrome/Edge 83+, Opera 69+, Samsung Internet 13+, and newer Firefox and Safari releases. | FAST creates a Trusted Types policy when `globalThis.trustedTypes` exists and otherwise uses its string-based DOM policy. Apps that enforce `require-trusted-types-for` must configure an appropriate DOM policy before templates compile. |
+| `globalThis` | Required by FAST Element v3. The baseline versions above include native `globalThis` support. | FAST Element v3 no longer polyfills `globalThis`. Load a `globalThis` polyfill before importing FAST in older browsers or non-browser runtimes. |
+
+## SSR and hydration notes
+
+Client-rendered FAST Element components only need the baseline runtime features.
+Server-side rendering and hydration add browser and application requirements:
+
+* The server must emit FAST-compatible hydration markers and Declarative Shadow
+  DOM templates.
+* The browser must parse Declarative Shadow DOM before FAST elements connect.
+* The application must call `enableHydration()` from
+  `@microsoft/fast-element/hydration.js` before hydrated elements connect.
+* If hydration is not enabled, or if a template is not hydratable, FAST uses
+  client-side rendering for the element.
+
+Use client rendering, or provide an application-owned DSD transform/polyfill, for
+browsers that meet the baseline runtime requirements but do not support
+Declarative Shadow DOM.