diff --git a/apps/web/.env.example b/apps/web/.env.example
new file mode 100644
index 0000000..b2056fc
--- /dev/null
+++ b/apps/web/.env.example
@@ -0,0 +1,3 @@
+# Set to false to use the HTTP dataset API.
+# Default behavior uses the mock API.
+# VITE_USE_MOCK_API=false
diff --git a/apps/web/README.md b/apps/web/README.md
index 2411260..e442b6b 100644
--- a/apps/web/README.md
+++ b/apps/web/README.md
@@ -36,6 +36,18 @@ bun run typecheck  # tsc --noEmit
 
 ---
 
+## Dataset API mode
+
+By default, the app uses the local mock dataset.
+
+To use the HTTP API instead, create a `.env` file and set:
+
+```env
+VITE_USE_MOCK_API=false
+```
+
+---
+
 ## Ufazien Deployment
 
 This project is configured for deployment to Ufazien Hosting.