Comprehensive Explanation

Adobe Experience Manager provides dedicated client-library debugging functionality to help developers investigate problems involving JavaScript and CSS resources.

AEM client libraries use categories, dependencies, and embedding configurations to organize and deliver frontend resources. During processing, multiple source files may be combined or optimized, making it difficult to identify the underlying resource responsible for a problem.

The debugClientLibs=true query parameter activates a debugging mechanism that exposes information about the source files included within generated client-library resources.

The developer can append the parameter to the affected page URL:

/content/site/en/page.html?debugClientLibs=true

After reloading the page, the developer can inspect the generated resource references and determine whether the expected JavaScript and CSS files are included.

Option A may be useful when Dispatcher caching or resource delivery causes the problem, but it does not directly inspect the client-library compilation process.

Option B helps detect runtime JavaScript errors, although it may not establish why a client library was omitted.

Option C becomes relevant when resource-access permissions prevent client libraries from loading.

Verification qualification: Option D is the strongest AEM-specific diagnostic approach, but enabling debugging does not automatically repair missing libraries. The developer must identify and correct the underlying problem, such as incorrect categories, missing dependencies, broken resource references, or stale caches.

Official Adobe Reference: Using Client-Side Libraries — Debugging Tools; Set Up a Local AEM Development Environment — Debugging Client Libraries.