diff --git a/common/README b/common/README
index 5653c2d0a..94d4a9725 100644
--- a/common/README
+++ b/common/README
@@ -3,6 +3,18 @@
Files used across all of the DocC catalogs to render custom/themed output.
- [Related documentation on theming DocC content](https://www.swift.org/documentation/docc/customizing-the-appearance-of-your-documentation-pages)
-- [OpenAPI spec of theme-settings.json schema](https://github.com/swiftlang/swift-docc/blob/main/Sources/SwiftDocC/SwiftDocC.docc/Resources/ThemeSettings.spec.json)
-The common files need to be copied, or perahps linked, into each of the DocC catalogs to keep a consistent flavor across them.
\ No newline at end of file
+The common files need to be copied, or perhaps linked, into each of the DocC catalogs to keep a consistent flavor across them.
+
+Both files are intentionally minimal:
+
+- `header.html` has no visible content. It's a reserved hook (DocC's
+ `custom-header` template) for a future documentation-version switcher —
+ add the switcher UI to the `#version-switcher` div when that lands.
+- `footer.html` is just a copyright line, styled with DocC's own CSS custom
+ properties (e.g. `var(--color-text)`) rather than hardcoded colors, so it
+ flips with the page's light/dark mode. It intentionally does not implement
+ a manual light/dark toggle: any custom-footer template suppresses DocC's
+ native `Footer` component (the one that implements the real toggle), so
+ color scheme here is auto-only, following the browser's
+ `prefers-color-scheme` via DocC's default CSS.
\ No newline at end of file
diff --git a/common/footer.html b/common/footer.html
index 3f71c547e..70299e272 100644
--- a/common/footer.html
+++ b/common/footer.html
@@ -8,365 +8,9 @@
See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
-->
-