diff --git a/npm/npm-test/action.yaml b/npm/npm-test/action.yaml
index adb1cb0..61705db 100644
--- a/npm/npm-test/action.yaml
+++ b/npm/npm-test/action.yaml
@@ -9,6 +9,10 @@ inputs:
     description: "Node.js version to use."
     required: false
     default: "20"
+  useDefaultRegistry:
+    description: "Whether to include https://registry.npmjs.org as a public (no-auth) registry. Values: true, false."
+    required: false
+    default: "true"
   registries:
     description: "Newline-separated list of registry URLs that require authentication."
     required: false
@@ -61,7 +65,13 @@ runs:
   - name: "Configure npm authentication"
     if: ${{ inputs.registries && inputs.apiKeys }}
     run: |
-      bash "${{ github.action_path }}/configure-auth.sh" add "${{ inputs.registries }}" "${{ inputs.apiKeys }}"
+      REGISTRIES="${{ inputs.registries }}"
+      API_KEYS="${{ inputs.apiKeys }}"
+      if [ "${{ inputs.useDefaultRegistry }}" == "true" ]; then
+        REGISTRIES=$(printf '%s\n%s' 'https://registry.npmjs.org' "$REGISTRIES")
+        API_KEYS=$(printf '%s\n%s' 'none' "$API_KEYS")
+      fi
+      bash "${{ github.action_path }}/configure-auth.sh" add "$REGISTRIES" "$API_KEYS"
     working-directory: ${{ inputs.workingDirectory }}
     shell: bash
   - name: "Install dependencies"