Warning: The following contains actual technical content. Side effects may include faster websites, happier users, and a sudden urge to explain bfcache at dinner parties.

Our latest round of optimizations helped nudge Core Web Vitals scores past the 80% mark across Duda sites, helping us maintain our position as the leading website building platform for CWV performance. This achievement was highlighted in the latest Core Web Vitals Technology Report (cwvtech.report).

To be clear, this milestone isn’t the result of one or two tweaks, it reflects years of foundational work focused on performance, from smart lazy loading and optimized JavaScript to recent, strategic enhancements under the hood. These latest changes, focused on how browsers cache and restore pages have helped us push past our previous benchmarks of 80% and move the needle even further toward 82%!

Why do Core Web Vitals still matter?

As a refresher, Core Web Vitals are a set of key metrics Google uses to measure real-world user experience:

• LCP (Largest Contentful Paint): How fast the main content loads
  
  
• INP (Interaction to Next Paint): How quickly the site responds to user input
  
  
• CLS (Cumulative Layout Shift): How visually stable the page is during loading
  
  

High CWV scores don’t just create smoother, faster experiences, they also contribute to stronger SEO performance and happier visitors who are more likely to stick around and convert.

Our latest Improvements that made a difference

Duda has recently implemented ETag headers and optimized its caching strategy by dropping the CCNS (Cache-Control: no-store) value, enabling the use of bfcache (back/forward cache). These changes have already proved to enhance website performance and user experience by reducing load times and improving page navigation.

What is CCNS and BFcache

Browsers use a helpful optimization called bfcache (back/forward cache). Bfcache stores a snapshot of a web page when you navigate away from it. This allows for instant navigation when you click the back or forward buttons in your browser, making browsing much faster.

In the past, Duda employed the `Cache-Control: no-store` directive (CCNS). This directive instructs the browser not to cache any version of the page to ensure sensitive or personalized information is not stored in browser caches. As a result, using `Cache-Control: no-store` also disabled the bfcache functionality.

Why the change?

Using BFCache (back/forward cache) is significantly better than a regular reload cache because with bfcache, the browser can restore the page from a stored snapshot. With BFCache the page doesn't need to be processed or have JavaScript executed again before rendering. In contrast, a regular reload cache (from http cache), while saving some bandwidth, still requires the browser to process the page and execute scripts. This processing takes time. Therefore, bfcache results in near-instantaneous page loads for back/forward navigation, while a regular cache still involves a loading delay, even if the resources are fetched from the cache.

Dropping CCNS now fully enables bfcache and users can expect significant improvements to navigation speed when navigating back or forward.

Protecting your data

`Cache-Control: no-store` was previously used to prevent caching of sensitive content, ensuring that browsers did not store copies. Simply dropping this header value can expose sensitive data if not handled carefully because the information may now be stored in caches, potentially leading to security vulnerabilities if those caches are compromised or accessed by unauthorized users. Duda now optimizes the use of the `no-store` value which will be retained for pages that require log-in or require on demand server computation like pages with personalization rules.

A Duda site getting more “back_forward_cache” navigation types once the header is removed: