Ad Tech & Ad Ops

How Ads Impact Core Web Vitals?

Learn how ads impact core web vitals and what publishers can do to mitigate the impact of ads on Google Core Web Vitals.

User experience quality optimisation is the key to the long-term success of any website. Google’s core web vitals can help you achieve those. Core Web Vitals don’t just affect the ranking factors but also the ad revenue.

But first thing’s first. 

What are Google Core Web Vitals?

Google core web vitals are the speed, responsiveness, image loading speed, etc., metrics that form a part of Google ranking signals to measure page experience.

In addition, Google has provided several tools to measure the site’s performance and give the publishers accurate reports based on which they can improve their site’s performance.

The current Google core web vitals focus on three aspects of user experience– loading speed, interactivity, and visual stability. 

1. Largest Contentful Paint (LCP) 

How many times have you clicked on a link but ended up leaving because it took ages to load? When you improve your LCP score, you increase the chance of visitors staying on your web page to consume content. 

In simple words, LCP measures how long it takes pages on your site to load. Of course, as users of a site, we want the web page to load right upon us clicking on it. Therefore, LCP focuses on core aspects that contribute to the quick loading speed of the web page.

The easiest way to see the speed metrics for your site is on Google Search Console> Core Web Vitals. You can easily see the pages ranked as ‘poor URLs’ or ‘URLs need improvement’ or ‘good URLs’. 

An ideal LCP measurement is less than or equal to 2.5 seconds

Read MoreLargest Contentful Paint: How to optimize LCP?

Impact of Ads on LCP:

Now LCP will be affected when a display ad takes long to render. It usually happens with the ads placed above the fold (ATF) and larger than other elements on the web page. 

So, to avoid that, publishers try to load ads as fast as possible just in time for the visitors to view them and click on them. 

You can refer to our article on Publisher Ad Audits to know your ads speed for better understanding. 

However, this strategy can increase the LCP score if the header bidding auction takes time. Because of this, your website’s network will have fewer resources to load the important content on the webpage and eventually, the LCP will be higher. 

To solve this issue, you can display ads below the fold to ensure that it loads faster. Make sure that the header bidding auction is not taking up too much time that it increases speed latency.

Read More: Website Speed Optimization Tools for Publishers to Check Out 

2. First Input Delay (FID)

Interactivity metrics get reviewed here- the time it takes for a page to become interactive is what the FID measures. FID score under 100 ms is good, and over 300 ms is poor. 

Read More: First Input Delay: How To Measure & Optimise FID

Examples of ways users interact with your site: 

  1. Clicking on a link on the site 
  2. Entering a phrase in the search bar on the site 
  3. Submitting their email into a field
  4. Opening an accordion text on mobile devices. 
  5. Choosing an option from the menu 
  6. User filling in an inquiry, etc. 

FID is just measuring how long it takes for something to happen on a page or the way page responds to the user’s request, which makes it similar to measuring page speed but a step ahead.

Impact of Ads on First Input Delay:

FID measures the time it takes for a user to do something on the page. 

Now, when you display ads, they can be responsive ads- they may require the user to interact with them, such as by clicking to play the video.

So, how can you mitigate the impact of the First Input Delay on your ad revenue?

1.  Third-party JavaScript Execution delay-

Ad serving comes with third-party ad tags and can add to the interaction latency by keeping the website’s network busy. In that case, you can remove the third-party javascript that is of no use. PageSpeed Insights tool can help you identify which elements serve any purpose and which are not. 

2.  Lazy Loading Optimisation: 

Lazy loading is the most common practice of publishers to improve page speed. By optimising lazy loading ads, you can deliver the content and ads just in time for the user’s view. This technique is highly recommended for ads below the fold and not for the primary viewport. 

Read about- Lazy Loading Ads: What, When, Where, Why & How

3.  Asynchronous Ad Tags loading:

With asynchronous loading of third-party ad scripts, you can prevent your content and ads from being blocked and slow loading. You can use-

<script async src=”

https://securepubads.g.doubleclick.net/tag/js/gpt.js”></script>

3. Cumulative Layout Shift

A few elements shift from their original place when the page loads, affecting the user’s interaction with the page. Cumulative Layout Shift measures the increase in times a web page’s frameshifts. 

Read More: Cumulative Layout Shift- How to optimize CLS?

And ads may add to these shifts on a webpage. If the publisher has not reserved ample space for the ad, they may shift the content, affecting the user experience. You can mitigate the CLS impact for a better user experience and ad revenue. 

1.  Expanding or collapsing an ad slot when a display ad is called- 

Many publishers tend to collapse the ad space when there is no ad to display; this may cause an unwanted or unexpected layout shift in the web page elements. 

To mitigate the CLS impact, publishers can use the Google Ad Manager Historical report to know the fill rate of ad slots- 

  • The ad spaces likely to be filled should be ‘expanded’, and 
  • The ad spaces unlikely to be filled should be ‘collapsed’. 

2.  Solution for Fluid Ad slots- 

Fluid ad slots do not specify fixed ad sizes because they automatically resize the ads to fit the creative content. This causes an unexpected layout shift because the publisher won’t know what size of space they need to reserve for the ad. For that:

  • You can use the fluid sizes for the ad slots that are not in the primary viewport but below the fold (BTF) 
  • You can fetch the ad slot as soon as the user views the page so that it’s already resized. 

3.  Solution for Adding multi-sized ad slots- 

Reserving ample space for the ads can avoid CLS but mostly for the static ad slots. Multi-size ad slots can be hard to accommodate. So for that multi-sized ad slots, you can:

  • Reserve space for the largest ad size;
  • Reserve space for the ads most likely to be served. 

Google Ad Manager report will help you understand the historical fill data and reserve space accordingly. 

With AdPushUp’s Ad Layout Optimisation, you can ensure that your ads don’t negatively impact the Google Core Web Vitals without hampering the user experience. To ensure a better ad experience and boost your ad revenue, you can request a free demo to get an approximate revenue uplift. 

Winding Up

As you may have figured, it’s not an easy job to optimise ads and improve google core web vitals. It requires a deep understanding of the user experience and ad experience. With Google Core Web Vitals, publishers can resolve the issues concerning their ad loading and, eventually, the ad revenue. 


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