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What is Cumulative Layout Shift?

All user experiences that are SEO-compliant, offered by websites to users, indirectly affect the SEO score. The concept of Cumulative Layout Shift , which is one of the new metrics that Google has recently applied on websites, measures the shift that reduces the satisfaction of the site visitors in the process of reading a content on the site.

In its abbreviated form, CLS helps to calculate the amount of shift by identifying key elements that are not visible in the first milliseconds of a page’s loading process, but then start to load and cause page shifts.

Normally, when you visit a website, the text part of the content loads quickly, but the videos or images that are at the beginning or within the content may not load at the same speed. In such cases, although users continue to read the content without waiting for the images to load, the moment the images and videos are loaded, a sudden shift occurs on the page, negatively affecting the user experience.

How to Calculate the Effect of Shift?

The shift effect known as “Impact Fractation” shows us how badly the display experience of the website is affected by the shift experienced on the websites. This means that by comparing the page image before the shift and the page image after the shift, it is possible to compare the difference, the areas displayed, and thus to learn what extent the bad impact occurred.

What Should Be Done To Have a Low Cumulative Layout Shift Score?

Cumulative layout shift control for which there are a number of issues that should be prevented from being measured and existing on the page. Unless you pay attention, CLS scores will definitely be high, and your site quality will decrease. We can summarize the tips that will reduce the CLS score as follows.

The dimensions of any advertisements, frames and placements on your web page should be determined. If it is published on the page without determining its size, these factors can create shifts as they will cause an increase in blank space when your page is opened. For this reason, besides the determination of these dimensions, all advertisements in the viewing area should not be viewed on the site.

Site speed is also very important in the calculation of this score, as it is important in every field. Slow loading sites will inevitably experience problems such as freezing and white space on the page, so the frequency of shifts is quite high. For this reason, it should be ensured that the site speed is at the required rate.

It has been observed that some of the fonts used in the content on the sites create a space during loading. In such cases, it is recommended to avoid fonts that will create shift in order to avoid problems with loading.

CLS score for which one of the issues that reveal undesirably high values is the dynamic elements in the content. Since these elements, which cause new content to be added automatically to the content, will also cause the current layout on the page to change, therefore, dynamic elements should be avoided except for the requests of the users.



Finally, the presence of images of unknown dimensions on the pages of the site increases the CLS score. In order to avoid this situation, it is recommended to specify the length and width dimensions of each image uploaded to the pages and to upload the CSS dimension ratios.

How is CLS Measured?

Cumulative layout shift measurement uses the formula of “shift effect x shift distance”.The dimensions of the frames and image areas that make up the image areas on the site are examined, and the movements of the problematic elements are examined. This situation, also known as “unstable”, means that the content is displaced on the site within milliseconds. While calculating the unstable state, the ratio of the shift distance created by the movement and the effect ratio should be multiplied to obtain the CLS score.

What are the meanings of the CLS scores?

Scores of 0.1 and below: Indicates that you have a good CLS score. It is very efficient in terms of SEO.

Scores between 0.1 – 0.25: It means that your site needs improvement.

Scores of 0.25 and above: It means poor cumulative layout shift score . On sites with CLS scores at these values, users are faced with a shift. It is recommended that you take immediate action regarding the issue.

What is Cumulative Layout Shift?