angular · weedorflow · Mar 26, 2026 · Mar 28, 2026 · Mar 28, 2026
diff --git a/adev/src/content/tools/libraries/creating-libraries.md b/adev/src/content/tools/libraries/creating-libraries.md
@@ -76,6 +76,64 @@ Anything exported from this file is made public when your library is imported in
 
 Your library should supply documentation \(typically a README file\) for installation and maintenance.
 
+### Creating secondary entrypoints
+
+A secondary entrypoint lets consumers import a distinct subset of your library, for example `my-lib/testing`, without pulling in the entire library bundle.
+
+To create one, follow these steps:
+
+**1. Create the entrypoint directory and files**
+
+Add a subdirectory under your library project with its own `ng-package.json` and `src/public-api.ts`:
+
+```text
+projects/my-lib/
+  ng-package.json
+  src/public-api.ts
+  testing/
+    ng-package.json
+    src/public-api.ts
+```
+
+**2. Configure `ng-package.json`**
+
+In the secondary entrypoint directory, set `entryFile` to point to its public API:
+
+```json
+{
+  "lib": {
+    "entryFile": "src/public-api.ts"
+  }
+}
+```
+
+**3. Export symbols from the public API**
+
+In `testing/src/public-api.ts`, export the symbols you want consumers to access from this entrypoint:
+
+```typescript
+export { MockMyLibService } from './mock-my-lib.service';
+export { MyLibHarness } from './my-lib.harness';
+```
+
+**4. Build the library**
+
+Build with the Angular CLI as usual — ng-packagr automatically discovers and compiles all secondary entrypoints:
+
+```shell
+ng build my-lib
+```
+
+**5. Use the secondary entrypoint in consuming applications**
+
+After building, consumers import from the secondary entrypoint using its subpath:
+
+```typescript
+import { MockMyLibService } from 'my-lib/testing';
+```
+
+For more details on how secondary entrypoints are resolved and when to use them, see [Entrypoints and code splitting](tools/libraries/angular-package-format#entrypoints-and-code-splitting) and [Resolution of secondary entry points](tools/libraries/angular-package-format#resolution-of-secondary-entry-points).
+
 ## Refactoring parts of an application into a library
 
 To make your solution reusable, you need to adjust it so that it does not depend on application-specific code.