Clientlib payload is one of the more controllable levers for AEM Core Web Vitals, and unlike backend performance tuning, most of the wins here do not require touching AEM internals at all.
Categorize before you minify
Split clientlibs by actual usage scope: truly global CSS/JS, page-type-specific bundles, and component-level bundles loaded only where the component appears. A common anti-pattern is a single monolithic clientlib category loaded on every page regardless of what that page actually uses.
Dependency graph discipline
Review the dependencies and embed properties in each clientlib's .content.xml periodically. It is easy for a dependency chain to accumulate unused embeds over time as components are added and removed, silently bloating every page that includes that category.
Async and defer loading
Not every script needs to block initial render. Identify JS that is not needed for above-the-fold content and load it with async or defer, or move it to a lazily-loaded clientlib category triggered after the initial page load completes.
CSS delivery
- Inline genuinely critical, above-the-fold CSS rather than waiting on a full stylesheet round trip
- Defer non-critical CSS (below-the-fold sections, rarely-used components) to a separate category
- Audit for unused CSS rules from old component versions that were never cleaned up during redesigns
Measuring impact
Use Lighthouse or a real-user-monitoring tool against actual production pages, not just a local dev instance without Dispatcher caching in front of it — clientlib minification and gzip behavior can differ meaningfully between environments, and local timings will not reflect what real users experience.
A realistic first pass
Start with your highest-traffic templates. Measure current clientlib payload size and render-blocking resource count, apply the categorization and async/defer changes above, then re-measure. This alone typically recovers a meaningful chunk of Largest Contentful Paint time on sites that have accumulated clientlib debt over several years of component additions.