Overcoming Core Web Vitals Challenges in Single Page Applications SPAs

When it comes to building Single-Page Applications (SPAs), developers face unique challenges in meeting the Core Web Vitals requirements. CWV, while crucial for optimizing website performance, were not initially designed with SPAs in mind. Google has made efforts to accommodate SPAs, but as of now, there is no straightforward way for SPAs to excel in this aspect. In this blog, we will explore the impact of SPA architectures on Core Web Vitals and discuss potential solutions to overcome these challenges.

  • by Karlijn Löwik
  • Published
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Overcoming Core Web Vitals Challenges in Single Page Applications SPAs

Understanding Core Web Vitals in SPAs

Core Web Vitals data is essential for evaluating a website's user experience. However, capturing this data becomes tricky in SPAs, which do not have traditional page loads. Instead, SPAs rely on route changes or soft navigations, making it difficult to convey to Google that a new page has loaded. Consequently, reliable Core Web Vitals data is not easily obtained for SPAs.

First page view matters

For SEO optimization, the first page view is crucial in SPA Core Web Vitals. Chrome captures data only from the initial page that a user lands on. Subsequent soft navigations are not registered, necessitating the optimization of every page for a first-time visit.

SPA front-loading challenges

One major hurdle for SPAs lies in their front-loading approach, where the entire application is loaded at once to speed up subsequent page views. Unfortunately, this front-loading strategy doesn't align well with Core Web Vitals, which only measures performance during the first page view. This disparity makes it challenging to achieve positive scores in Core Web Vitals for SPAs.

The (Near) future outlook

While Google is experimenting with defining soft navigations, any updates or changes in this regard won't reflect in the Chrome User Experience Report (CrUX) dataset in the foreseeable future. This means that SPAs will continue to face challenges in this area for some time.

Chrome's Mitigations for SPAs

To avoid penalizing SPAs too severely, Chrome has introduced some mitigations. For instance, Largest Contentful Paint (LCP) stops being tracked after user interaction, preventing new LCP candidates from being identified during soft navigations. Similarly, Cumulative Layout Shift (CLS) is modified to consider only the most extreme five-second window, reducing the impact of constant updates throughout the SPA lifecycle.

Existing Limitations:

Despite Chrome's mitigations, certain Core Web Vitals metrics, such as First Input Delay and Interaction to Next Paint, remain unaffected. Moreover, the fact that SPAs are predominantly measured only on the first page in a session means that subsequent metric updates might count against the initial URL, leading to distorted results.

Potential solutions in passing Core Web Vitals with your SPA:

  1. Consider Moving to an MPA: In many cases, transitioning to a Multi-Page Application (MPA) might be a more viable option. MPAs are better suited for meeting Core Web Vitals requirements and can offer improved performance.
  2. Optimize Heavily for First Visits: Focusing on optimizing the first page view can positively impact Core Web Vitals scores. While this approach captures limited data per session, it aligns well with current SPA challenges.
  3. Stay Informed and Patient: Keep an eye on new APIs and updates that Google might introduce to address SPA-specific Core Web Vitals challenges. As the web platform evolves, there is hope for better integration of SPAs into the Chrome User Experience Report.

Conclusion:

Building SPAs presents unique obstacles when it comes to meeting Core Web Vitals thresholds. While Google has made efforts to accommodate SPAs, the challenges persist. Considering alternative approaches, optimizing for first visits, and staying informed about potential updates can help navigate the current landscape. As the web ecosystem evolves, there is optimism that better solutions will emerge to make SPAs more Core Web Vitals-friendly.

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