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Last month, our team joined forces with Google for a webinar introducing some of our latest findings regarding the impact of a Consent Management Platform (CMP) on web performance, particularly Interaction to Next Paint (INP), the latest Core Web Vital implemented by Google, which assesses a page's overall responsiveness to user interactions.
The speaker's panel consisted of members from Google and Didomi, discussing Core Web Vitals and the work the Didomi team has done over the past year to improve our CMP performance in that regard.
You can access the full recording below or keep reading for a complete breakdown.
Introduction to Core Web Vitals and web performance
Web performance is a topic we’ve addressed at Didomi in the past and are constantly working on. An integral part of it is Core Web Vitals, an initiative by Google to provide a set of metrics to measure and qualify user experience online by assessing the loading, interactivity, and visual stability of web pages.
At the moment, there are three core web vitals metrics:
- Largest Contentful Paint (LCP) measures how fast a website loads.
- Interaction to Next Paint (INP) measures the responsiveness of a page.
- Cumulative Layout Shift (CLS) measures the visual stability of a page.
Your overall score for these metrics indicates how smooth your website's browsing experience is. It will not only illustrate the quality of the user experience, but also impact your search results ranking on Google.
In this webinar, our speakers focused specifically on INP (Interaction to Next Paint), the latest Core Web Vital added in 2024. INP measures a page's responsiveness by assessing the time it takes for the next frame to be painted following a user interaction, such as clicks, typing, or other input events.
This not only has an impact on user experience but can also have a significant business impact, as explained by Thierno Thiam, Web Ecosystem Engineer at Google:
“When you start measuring or improving INP, you will start to make your user experience better, but potentially you could also improve some business KPIs. Case studies have already proven a strong relationship between INP and business metrics.
For instance, when the Economic Times started improving INP, it saw a 50% decrease in bounce rate on their website but also a 43% page views uplift.”
Thierno Thiam, Web Ecosystem Engineer at Google
To get a snapshot of your website performance, Google provides PageSpeed Insights, a free tool to analyze Core Web Vitals performance on a given URL. However, as Thierno Thiam mentions during the webinar, this only provides a simple, limited vision, and data should be measured in the field for more.
To learn how to improve your INP score, Google recommends some key steps, which you can find on the organization’s web.dev website: How to optimize INP?
The role and impact of Consent Management Platforms (CMPs) in web performance
Consent Management Platforms (CMP) like ours at Didomi have become critical components of the web ecosystem and can significantly impact Core Web Vitals:
- LCP: CMPs may introduce additional JavaScript and CSS, delaying rendering the largest contentful element. Depending on the format, the consent banner can sometimes even be considered the largest element on the page.
- INP: CMPs can increase input latency by triggering additional client-side scripts when users choose their consent on the banner.
- CLS: CMPs generally do not affect CLS, with some exceptions depending on the implementation of the CMP.
At Didomi, we also look at additional metrics that are relevant specifically to CMP:
- Total Block Time (TBT): This metric measures the total time between two critical points during page loading: First Contentful Paint (FCP), when the first visible content appears on the screen, and Time to Interactive (TTI), when the page becomes fully interactive. TBT specifically tracks how long the main thread was blocked during this period, causing the page to be unresponsive to user actions.
- CMP Ready Time: This is a Didomi-specific metric that measures the time it takes the CMP to be ready and initialized on the page.
While there are best practices organizations can follow (more on that below), our Chief Technical Officer Jawad Stouli warns that an INP score doesn’t tell the whole story and that attribution is vital to identifying the source of potential issues:
“As is very often the case when we talk about performance, there isn’t a single, easy way to define the impact of a CMP on the web performance of a website. As you can see, CMPs will impact different metrics in different ways, for different reasons, and the exact impact will vary on the CMP configuration, the website itself, and the interactions between the two."
- Jawad Stouli, Chief Technical Officer and co-founder at Didomi
With that in mind, let’s pull back the curtain and take a closer look at some of the experimentations we’ve implemented to improve our customers' performance and the preliminary results we can already observe.
CMP best practices for Core Web Vitals and performance: How we do it at Didomi
To ensure your customers can benefit from the best web performance possible, the Didomi team has dedicated significant resources to fine-tuning to adapt to Core Web Vitals, especially the newly released INP.
These are some of the steps our product and engineering teams have taken over the past year and a half:
The latest improvement, which has since been released and activated for all Didomi customers, is the performance.yieldOnConsent flag that yields specific code executions to break tasks into small operations, as explained during the webinar by our Lead Product Manager, Julie C:
“This new flag we delivered in June aims to significantly enhance the performance of interactive actions on a website, to offer a smoother and more interactive experience. Our internal testing is pretty positive and shows a 60 to 70% improvement in the average INP score for CMP-related actions.”
- Julie C, Lead Product Manager at Didomi
The implementation of these changes has had an observable impact on our CMP Core Web Vitals performance, showcasing an uplift directly related to the efforts of our team:
Adding to the positive results, our Product Marketing Manager, Desirée Blank, highlights once again that although your CMP likely has an impact on your Core Web Vitals performance, it is only one of many third-party technologies on your website that do, something that she has observed in working with Didomi partners and customers:
“As we’ve been working with customers to define how we’re going to improve, we’ve seen the challenges they face in often balancing changes within the CMP, other technologies and often their own website. (...) For example, a custom UI or the number of vendors that will impact the CMP performance. They are outside our control, but we have incorporated them in our best practice guides for you to continue optimizing your INP scores.”
Desirée Blank, Senior Product Marketing Manager at Didomi
She also explains that organizations must find the right balance between iterations that might benefit their Core Web Vitals performance but could be detrimental to their consent rate performance, which we’ve looked at in our last consent benchmark on consent collection in Europe:
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What can Didomi clients do to improve their Core Web Vitals and INP?
With these improvements in mind from Didomi, what steps can you take to improve your INP and Core Web Vitals score as a Didomi customer?
Hernan Onzalo, Engineering Manager at Didomi, lists four key elements to take into account:
- Limit the number of vendors and purposes in your consent banner (learn how here).
- Don’t load third-party scripts immediately, as they pollute the main thread.
- Avoid custom UI implementations or apply best practices for buttons, links, and anything that triggers an action.
- Ensure that callbacks and other actions don’t block the main thread.
Following these recommendations, Hernan Onzalo ran a live demo demonstrating the impact of yielding on INP by comparing two similar websites with different implementations. To watch the live demo, head to the specific section of the recording:
As a Didomi customer, you can access ongoing support in your optimization efforts. Please reach out to your account manager with any questions you might have. Optimization is an ongoing work that we are committed to pursuing, and we will keep you updated.
To get involved with our efforts and provide feedback on your own optimization work with the Didomi CMP, please reach out:
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Frequently Asked Questions (FAQ)
What is INP, and why is it important?
INP (Interaction to Next Paint) is a Core Web Vital that measures how responsive a web page is to user interactions. It's crucial because it impacts user experience and can influence business metrics like bounce rate and page views.
How does a CMP affect Core Web Vitals like INP?
A CMP can affect INP by introducing additional scripts that increase input latency. It can also impact other Core Web Vitals like LCP (Largest Contentful Paint) by delaying content rendering.
How can I check my website’s Core Web Vitals performance?
You can use Google’s PageSpeed Insights tool to analyze your website’s Core Web Vitals, including INP. However, measuring in the field is recommended for a more detailed analysis.
What can Didomi clients do to improve their INP scores?
Didomi clients should limit the number of vendors in their consent banners, be mindful of their custom UI implementations, ensure that callbacks and other actions don’t block the main thread, and avoid loading third-party scripts immediately to keep the main thread responsive.
Learn more in our documentation, and contact your account manager if you have any further questions.
