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Journey ads and CLS

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Meghan Birnbaum

I'm getting an error in my Core Web Vitals that says “CLS issue: more than 0.1 (mobile)." After looking into it, it's been an issue since I added Journey and says it could be a third party ad issue. Any way to resolve this?

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    Support
    • Journey Support Team

    Hi Meghan Birnbaum ! While some ads could have a very minimal impact on CLS (typically no more than .01), most have no impact at all and they shouldn't be the primary cause of CLS failing on a site. We have over 3,000 sites on Journey and 13,000 on Mediavine, and in our testing and reporting we haven't found ads to be the main culprit when a site fails CLS since our inview ad boxes are specifically designed specifically to prevent CLS.

    That said, if the ad script is getting optimized, it's possible this could impact how assets load in and could result in issues. Here's an article that goes over how to check for script optimization conflicts and exclude the script from optimizations.

    We also have a post here with page speed resources that goes a little more in depth about our script and page speed. It links to this great help article on our most frequently asked site speed questions as well. Here's one relevant excerpt for your convenience:

    ---

    Let’s get to the most important question first: are ads the reason that your site is slow or failing Core Web Vitals?

    The short answer is no - Journey ads should never be the culprit of failing Core Web Vitals and have a negligible impact on site speed.

    While ultimately a site without ads will always be faster than one with ads – no matter what your setup is – Journey follows Mediavine technology and it is the fastest in the industry, we've built it with page speed at top of mind. What does this mean? 

    First, all our ads are lazy loaded and the associated scripts are asynchronous, meaning they don’t slow down the initial page load of the site or block the main thread. We also reserve space ahead of time throughout a post’s HTML and load ads in ad boxes with a specified width and height so they don’t cause any layout shifts.

    For these reasons, a well-optimized site on a lightweight theme shouldn’t have issues with speed performance or with passing Core Web Vitals while running Journey ads.

    ---

    It's also important to keep in mind that Core Web Vital metrics are the average of the past 28 days. 

    This means that if a few days after launching ads a CWV metric starts to fail, this would indicate that you’re failing that metric for reasons outside of ads.

    If you start failing a few weeks after running ads though, there can be a few reasons you start seeing a CWV metric fail. 

    1. The first is that other changes were made on your site around the same time you launched ads that are causing CWV metrics to fail. The best way to figure out if this is the case is to keep a log of changes you make on your site that you can reference if you ever start to see your CWV scores increasing. As an example, if you added a plugin and 28 days later started failing a metric, disabling that plugin and testing the site without it would be a great first step.
    2. The second is that your site was already right on the cusp of failing a specific metric, and the extra scripts needed to load ads pushed it that last ~1% into the failing zone. For example, if you already have a CLS score of .09, it’s possible ads could add .01 CLS, which would result in a “needs improvement” CLS score of .1. In a vacuum though, .01 is an incredibly small amount of CLS, and ads should never cause a site to fail a metric on their own. So if this happens, we encourage publishers to look at other opportunities for improvement.
    3. The script is being optimized and this is causing issues, as stated above in this post.

    ---

    Finally, if you're looking to troubleshoot CLS a bit further, here's more information on its usual causes and how to troubleshoot them:

    Failing CLS is usually caused by:

    1. Animations
    2. Font flashes
    3. Images, videos, or embeds without a set height or width
    4. Third party content that’s dynamically inserted on the page 

    Troubleshooting CLS:

    • Don’t load dynamically injected content (i.e. iFrame embeds) in the first screenview
    • Make sure images and videos have explicitly set sizes and aspect ratios
    • Use web safe fonts
    • Remove pop ups or animations that cause layout changes
    • If the site uses critical CSS, make sure the critical CSS file isn’t missing elements in the first screenview

    I hope this information helps!

Journey is Self Supported

Our support staff is monitoring this forum everyday for bugs related to ad delivery, the display and functionality of the Journey dashboard, and any bugs related to the onboarding process. We are typically unable to assist with non-bug related issues like RPM performance expectations, issues setting up the ads.txt file, and questions already answered by our existing help docs. Read here for a more detailed breakdown of how Journey is self-supported and our recommendations for how to find answers to common issues.

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