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In recent years, the SEO landscape has been revolutionized by the introduction of Google's Core Web Vitals , key metrics for measuring the quality of a website's user experience. Traditionally, many sites have opted to install additional services, such as e-commerce or blogs, in subdirectories of their main domain, a move deemed beneficial for SEO. However, with Core Web Vitals now official ranking factors, it's time to reconsider this strategy. We'll explore how subdirectory installation can negatively impact a site's overall SEO score and evaluate the option of using separate third-level content.
Core Web Vitals: What They Are and How They Work
Core Web Vitals are a set of specific metrics defined by Google to evaluate a user's experience on a web page. These include:
- Largest Contentful Paint (LCP): Measures the time it takes to load the main content of a page. A fast loading time is indicative of a good user experience.
- First Input Delay (FID): Evaluates the time it takes for a page to become interactive. The shorter this time, the better the experience for the user.
- Cumulative Layout Shift (CLS): Quantify the visual stability of the page while loading. A stable page improves the user experience by avoiding accidental clicks.
These metrics are primarily collected via Chromium-based browsers, which send data to Google. This reporting process allows Google to understand the efficiency of a web page from the end user's perspective.
Chromium-based browsers use a mechanism called “User Experience Reporting” (CrUX) to collect data related to Core Web Vitals and send it to Google . This reporting process plays a crucial role in determining the effectiveness of a web page from the end user's perspective. Below, we detail how this data is sent:
- Background Data Collection: As users browse the web, Chromium-based browsers collect anonymous data about the performance of the pages they visit. This data includes metrics like Largest Contentful Paint (LCP), First Input Delay (FID), and Cumulative Layout Shift (CLS), which are indicative of the user experience on each page.
- Using HTTP Beacons: To transmit this data to Google, Chromium uses “HTTP beacons”. Beacons are small network requests sent by your browser to Google's server. These requests are designed to be lightweight and non-blocking, meaning they can be sent in the background without affecting the user's browsing performance.
- Data Format and Transmission: The collected data is compacted into a format that reduces its weight, while maintaining all essential information. When the browser detects an appropriate moment, it sends the collected data to the Google server using beacon technology. This time is generally chosen to minimize the impact on browser performance, for example when the network is less congested.
- Processing and Anonymization: Once received by Google, the data is processed to ensure user anonymity. Google aggregates performance data from multiple users to avoid identifying individuals. Only after this aggregation, the data is used to analyze web page performance trends globally.
- Feedback to Developers and SEOs: Through tools like Google PageSpeed Insights and other SEO reports, Google makes analyzes based on the data collected available to web developers and SEO professionals. This allows them to identify performance issues on their pages and implement targeted improvements to optimize them Core Web Vitals.
- Impact on Ranking: Google uses this aggregate information in its algorithms to influence the ranking of pages in search results. The pages that show best Core Web Vitals they tend to have better rankings, reflecting the importance of a good user experience.
Hypothetical Case Study: WordPress Blog and WooCommerce Shop
Let's consider a purely hypothetical case of the example.it site, which hosts a blog on WordPress and decides to integrate a WooCommerce shop in the example.it/shop/ subdirectory, rather than opting for a third level, such as shop.example.it.
The choice of this configuration implies a series of technical and strategic considerations that are very relevant for the overall performance of the site and its SEO positioning.
First, site performance: web page loading speed is crucial for a good user experience and Google rankings. If the shop section, hosted in the subdirectory, isn't optimized for loading speed, it can be significantly slower than other parts of the site. This performance discrepancy can directly impact the Core Web Vitals , the metrics Google evaluates to determine the quality of the user experience. Since Google considers site performance holistically, even a single under-optimized section, such as the online store, can lower the overall Core Web Vitals score for the entire domain. This drop in rating can lead to a decline in the site's ranking in search results.
On the other hand, the SEO implications of such a configuration are significant. When Google crawls a site, it treats the entire domain as a single entity, and the performance of one section of the site can impact the entire domain. Therefore, if a subdirectory like /shop/ exhibits slow loading times or stability issues, these inefficiencies negatively impact the entire site. This means that, while the homepage or other sections can be optimized for fast loading times and a fluid user interface, the presence of a slower section can lower the site's perceived quality in Google's eyes, thus negatively impacting the domain's overall visibility in search results.
Specifically, here are the two problems:
- Site Performance: If the shop section is less optimized and slower, it will negatively affect i Core Web Vitals of the entire domain. Google evaluates site performance holistically, which means that a slow part of the site can lower the overall SEO score.
- SEO implications: A poorer installation in a subdirectory can hurt your domain's overall visibility in search results, despite optimization efforts on the home page or other fast sections of the site.
A highly skilled system administrator could make a compelling case for using advanced caching technologies, such as Varnish, to significantly speed up a site's shop section , making it comparable in speed to a blog section. Varnish can cache static web pages and serve them quickly, drastically reducing Time to First Byte (TTFB) and improving the overall user experience. This can be extremely effective for blog pages, where content doesn't change frequently and can be easily cached and served to users without requiring server processing each time.
However, it's essential to consider the inherent limitations of e-commerce and the implications of caching in this context. Caching cannot be used in the same way in critical sections of an e-commerce site, such as the login, shopping cart, and checkout pages . These pages require dynamic user interaction and often contain sensitive and personalized information that varies from user to user and from session to session. For example, a user's shopping cart contents or payment details must be managed in real time, making caching impractical.
Under these circumstances, the site's responsiveness depends entirely on the native speed of the application itself, without the support of caching technology. Therefore, while parts of the site like the blog can benefit from extremely fast loading times with a TTFB of around 50 ms thanks to aggressive caching strategies, dynamic e-commerce sections will operate at a much slower speed, tied to the intrinsic performance of the server and web application. This performance gap can negatively impact the overall user experience and, consequently, the site's Core Web Vitals , directly impacting SEO rankings.
Additionally, these dynamic areas of e-commerce are particularly sensitive to traffic variations, which can further degrade performance during peak access, such as during promotions or special events.
Extension of the Problem to slow parts and not just e-commerce.
The problem of negatively impacting Core Web Vitals isn't limited to a site's e-commerce sections, but also extends to other complex and dynamic areas such as logged-in user areas, membership platforms, and control panels. These sections, due to their inherently dynamic and personalized nature, often can't effectively benefit from caching strategies. This is because the data displayed is unique to each user and must be generated in real time, requiring constant interaction with the database and the site's backend.
For example, control panels (such as WordPress's wp-admin), frequently used by site administrators, can become particularly problematic. These panels are often designed without specific optimization for speed, as functionality and security are typically prioritized. If multiple users, particularly administrators or content managers, access these areas using Chromium-based browsers, their use could be tracked and detected as part of the site's overall user experience . Consequently, if these sessions are slow and inefficient, they could send negative signals to Google, negatively impacting Core Web Vitals and, by extension, the site's ranking.
An effective mitigation strategy for these issues could be to adopt browsers that do not participate in sending Core Web Vitals metrics to Google. For example, encouraging the use of browsers like Firefox, which currently does not contribute to the collection of Core Web Vitals data sent to Google, could be a practical solution.
Using Firefox, administrators and team members can access control panels and manage site functions without their activities impacting performance as perceived and measured by Google.
This allows you to separate the often less optimized backend performance from the influence on the site's performance metrics displayed to the public and evaluated by search engines.
Conclusions and Recommendations
When a significant portion of a site's traffic is concentrated in less performing areas, such as an online store, isolating these services on a separate third tier becomes a very effective strategy. This approach allows you to segregate the site's resource-intensive or slow-performing components, such as checkout or product viewing pages, from the rest of the site, which could be optimized for speed and efficiency.
Isolating your store on a subdomain, such as shop.example.com, can offer numerous technical and SEO benefits . From a technical standpoint, this separation allows for specific server configurations optimized for e-commerce needs, such as customized cache management, user session optimization, and transaction security. This can significantly improve the performance of e-commerce pages without impacting the main site, which can be configured more streamlined and faster to optimize static content such as blog posts, informational landing pages, and more.
From an SEO perspective, keeping your main site fast and responsive is crucial, as it's often the first interaction a user has with your brand through organic search. A fast main site not only improves the user experience, but also positively impacts Core Web Vitals , factors now considered by Google for ranking in its SERPs (Search Engine Results Pages). Connecting the main site to the shop's subdomain through direct links, such as promotional banners, navigation menus, or specific calls-to-action, makes it easier for users to access the e-commerce sections without compromising the performance of the main site.
This configuration helps maintain a balance between maintaining high performance for the main site and providing the necessary functionality and management capabilities for the e-commerce sections of the site. Furthermore, this clear and defined separation between content allows Google to evaluate the performance of the main site independently of any potential overhead introduced by e-commerce features. This ensures that any slowdown on the subdomain does not penalize the main domain, preserving its ranking and visibility.
