diff --git a/packages/northstar/src/views/preview.r.ts b/packages/northstar/src/views/preview.r.ts
index d7789b4..ea484cb 100644
--- a/packages/northstar/src/views/preview.r.ts
+++ b/packages/northstar/src/views/preview.r.ts
@@ -25,7 +25,7 @@ let errorMsg = "";
 export async function startPreview() {
   const compiler = new Compiler(currentProject.toOutput());
   compiler.runtimeModuleURL = runtimeURL;
-  code.js = transformer.transform("$", await compiler.compile());
+  code.js = "window.__QUASI_PREVIEW__ = true; \n\n" + transformer.transform("$", await compiler.compile());
   code.css = (
     await compileTailwindCSS(
       `@tailwind base;
diff --git a/packages/runtime/src/types/env.ts b/packages/runtime/src/types/env.ts
new file mode 100644
index 0000000..5385489
--- /dev/null
+++ b/packages/runtime/src/types/env.ts
@@ -0,0 +1,6 @@
+declare global {
+  interface Window {
+    __QUASI_PREVIEW__: boolean;
+  }
+}
+export {};