Deep Dive into Core Web Vitals and Their Importance

Core Web Vitals have become a critical metric for both user experience and search engine ranking. Google’s Page Experience Update directly incorporates these metrics into its ranking algorithm, meaning poor Core Web Vitals can negatively impact organic search visibility, traffic, and ultimately, ad revenue. Furthermore, slow-loading and unstable sites can lead to increased bounce rates, lower engagement, and reduced conversion rates, making CWV optimisation essential for any publisher focused on sustainable revenue growth.

Optimizing Core Web Vitals is essential for enhancing user experience and boosting your site's search engine rankings. Here are effective strategies to help you improve these critical metrics:

1. Largest Contentful Paint (LCP) – Loading Performance
   • Measures how long it takes for the largest visible content element (e.g., an image, video, or text block) to fully render on the screen.
   • How client-side bidding affects LCP: Too many client-side ad calls delay LCP by overwhelming the browser with multiple JavaScript requests from various demand partners.
   • How server-side bidding helps: Offloading ad requests to the server-side reduces browser processing time, helping to achieve a faster LCP.
2. Interaction to Next Paint (INP) – Interactivity
   • INP measures the latency of all user interactions (clicks, taps, and keyboard inputs) throughout a session and reports the longest duration observed, making it a more comprehensive assessment of a site’s responsiveness.
   • How client-side bidding affects INP: When too many demand partners are loaded on the client side, JavaScript execution delays browser responsiveness, increasing INP scores.
   • How server-side bidding helps: By handling complex calculations and bidding logic on the server, less processing is required on the client-side, which can improve responsiveness and reduce delays between user interactions and visual updates, enhancing INP.
3. Cumulative Layout Shift (CLS) – Visual Stability
   • Measures unexpected shifts in content layout, usually caused by late-loading ads or elements dynamically injected into the page.
   • How client-side bidding affects CLS: If ads load too late due to delayed auctions, page elements shift, causing negative user experiences.
   • How server-side bidding helps: Speedier ad loading through server-side processing reduces the impact on the page layout, minimising the chances of content shifting and thus improving CLS.

Repercussions of Poor Core Web Vitals

If a website fails to meet Core Web Vitals benchmarks, the consequences can be severe:

• SEO and Traffic Loss
  • Google prioritises fast-loading, stable websites in its search rankings.
  • Poor CWVs can push sites lower in search results, leading to reduced organic traffic.
• Higher Bounce Rates & Reduced Engagement
  • Studies show that 53% of mobile users leave a page if it takes longer than 3 seconds to load.
  • Sluggish performance discourages users from interacting with content or returning in the future.
• Lower Ad Revenue & Monetisation Impact
  • Slow-loading pages reduce viewability scores, leading to lower CPMs (Cost Per Mille) and fewer bid opportunities.
  • Poor INP and CLS can contribute to accidental clicks, which advertisers penalise, decreasing fill rates.

The Role of Server-Side Bidding in Improving Core Web Vitals

A major contributor to poor Core Web Vitals is excessive client-side demand partner requests. Every client-side auction involves multiple demand sources sending JavaScript-heavy ad calls, which significantly increases browser latency. This leads to delayed ad rendering, reduced interactivity, and poor layout stability—all of which degrade CWV scores.

By migrating demand partners to server-side bidding, publishers reduce browser workload, leading to:

✅ Faster LCP – Less JavaScript overhead means main content loads faster.

✅ Lower INP – Reduced client-side execution time improves page responsiveness.

✅ Better CLS – Ads are rendered more predictably, minimising disruptive layout shifts.

Illustrative Case Study:

A rigorous deployment of server-side bidding strategies at Pubstack demonstrated not only a marked improvement in Core Web Vitals but also a steadfastness in revenue performance:

• Largest Contentful Paint (LCP) improved by 7%, significantly speeding up the main content delivery.
• Interaction to Next Paint (INP) improved by 44%, greatly enhancing the site’s responsiveness to user inputs.
• First Input Delay (CLS) reduced by 50%, indicating a quicker visual readiness for user interactions.
• Importantly, during this period, ad revenue metrics were closely monitored and showed no detrimental effects; indeed, in several instances, revenue either maintained its previous levels or showed an increase, attributing to the optimised efficiency of ad delivery and improved user engagement.

Enhancing Server-Side Efficiency with Pubstack’s Ad Management for Server-Side solution

Pubstack simplifies the complexities of server-side ad management, providing an intuitive and easy-to-use platform that allows publishers to set up and manage server-side bidders effortlessly. Publishers benefit from reduced operational complexity, lower latency, and the ability to optimise ad monetisation without extensive technical expertise.

Real-Time Bidder A/B Testing and bidder insights

Pubstack enables publishers to instantly A/B test bidders on the server-side, helping to find the optimal balance between revenue and performance within hybrid setups. With real-time data available on our analytics dashboards, publishers can fine-tune their setups by adjusting bidder configurations, tracking revenue impact, and ensuring a seamless ad experience.

The Right Ad Setup for the Right Context

For mobile users, where high latency can impede ad loading speeds, Pubstack allows you a server-side only stack to enhance performance by minimising delays. This approach leverages server-side bidders exclusively for mobile visitors, ensuring seamless ad delivery. Conversely, for desktop users, a mixed stack that incorporates both client-side and server-side bidding can be used. This mixed approach allows for greater flexibility and optimisation, accommodating the generally lower latency on desktops and enabling a balanced strategy that maximises revenue potential.

Core Web Vitals Analytics

Pubstack’s Core Web Vitals dashboard offers full transparency on Core Web Vitals performance while bringing together revenue performance metrics. This comprehensive view allows publishers to monitor LCP, INP, and CLS in, ensuring that monetisation strategies do not come at the expense of user experience. By integrating revenue data with CWV scores, publishers can adopt data-driven optimisation strategies, ensuring continuous improvements in ad delivery efficiency and site performance.

Maximising Revenue with Advanced Yield Optimisation

Even after achieving the right balance between client and server-side bidding, publishers can further scale their revenues with multiple optimisation tools available within Pubstack's ad management platform. These tools ensure that ad performance continues to evolve, maximising both user experience and monetisation efficiency.

• Dynamic price optimisation to ensure optimal bid values.
• Lazy loading strategies to enhance ad viewability.
• Ad refresh technology to maximise impressions per session.

Conclusion

Server-side bidding emerges not just as a technology solution but as a strategic imperative for publishers aiming to thrive in the competitive landscape of digital media. With Pubstack’s server-side ad management, publishers gain access to a hassle-free, fully optimised platform that simplifies implementation, provides real-time insights, enhances ad performance, and expands monetisation opportunities. By leveraging automated optimisation and a streamlined marketplace, publishers can achieve sustained revenue growth while improving site performance, ensuring long-term success in the ever-evolving digital advertising landscape.