diff --git a/README.md b/README.md
index e8240fc..89e5b4e 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,13 @@ It aims to inform on the impacts on consumers, developers, states and coordinate
 3. Make the changes.
 4. Create a pull request.
 
+## Adding the Banner to Your Sites and Repos
+
+If your project is affected by the upcoming Android installation restrictions, you can help raise awareness by adding a banner.
+
+- **Websites** — [Add the countdown banner](https://keepandroidopen.org/banner)
+- **READMEs** — [Add a markdown callout](https://keepandroidopen.org/readme-callout)
+
 ## Running the site locally
 
 This is an Astro site, so you should be able to check out your fork locally and run it as per the [docs](https://docs.astro.build/en/develop-and-build/#start-the-astro-dev-server) with:
diff --git a/src/content/pages/banner.md b/src/content/pages/banner.md
index df3f834..4f4f443 100644
--- a/src/content/pages/banner.md
+++ b/src/content/pages/banner.md
@@ -64,3 +64,17 @@ Minimal size without animations.
 ## Source
 
 The source for the banner can be found at [https://github.com/keepandroidopen/keepandroidopen.github.io/blob/main/public/banner.js](https://github.com/keepandroidopen/keepandroidopen.github.io/blob/main/public/banner.js). Suggestions for improvement are welcome!
+
+---
+title: "Add a Warning to Your README"
+description: "A simple markdown callout to warn users that your app may be affected by Android's 2026 installation restrictions."
+lang: en
+---
+If your app can be installed outside the Google Play Store, it may stop working on Android in 2026 due to Google's upcoming installation restrictions. You can help raise awareness by adding the following callout to your README.
+## Callout
+```markdown
+> [!IMPORTANT]
+> **Android application installation restrictions are coming in 2026.**
+> This app may be affected by upcoming changes to Android that limit how applications can be installed outside the Play Store. Visit [keepandroidopen.org](https://keepandroidopen.org) to learn more and take action.
+```
+This renders as a highlighted callout on GitHub, GitLab, and most other platforms that support the `[!IMPORTANT]` syntax. On platforms that don't, it falls back gracefully to a plain blockquote.
diff --git a/src/content/pages/readmecallout b/src/content/pages/readmecallout
new file mode 100644
index 0000000..8b13789
--- /dev/null
+++ b/src/content/pages/readmecallout
@@ -0,0 +1 @@
+