diff --git a/aio/content/guide/file-structure.md b/aio/content/guide/file-structure.md
index e93618826c..0371550b5d 100644
--- a/aio/content/guide/file-structure.md
+++ b/aio/content/guide/file-structure.md
@@ -90,6 +90,7 @@ Angular components, templates, and styles go here.
 | `app/app.component.css`     | Defines the base CSS stylesheet for the root `AppComponent`. |
 | `app/app.component.spec.ts` | Defines a unit test for the root `AppComponent`. |
 | `app/app.module.ts`         | Defines the root module, named `AppModule`, that tells Angular how to assemble the application. Initially declares only the `AppComponent`. As you add more components to the app, they must be declared here. |
+| `app/package.json`              | This file is generated only in applications created using `--strict` mode. This file is not used by package managers. It is used to tell the tools and bundlers whether the code under this directory is free of non-local [side-effects](https://webpack.js.org/guides/tree-shaking/#mark-the-file-as-side-effect-free). |
 
 ### Application configuration files