Case Research: How the Cookie Monster Ate 22% of Our Visibility


The writer’s views are fully his or her personal (excluding the unlikely occasion of hypnosis) and should not all the time mirror the views of Moz.

Final yr, the group at Homeday — one of many main property tech firms in Germany — made the choice emigrate to a brand new content material administration system (CMS). The targets of the migration had been, amongst different issues, elevated web page velocity and making a state-of-the-art, future-proof web site with all the mandatory options. One of many predominant motivators for the migration was to allow content material editors to work extra freely in creating pages with out the assistance of builders. 

After evaluating a number of CMS choices, we selected Contentful for its trendy expertise stack, with a superior expertise for each editors and builders. From a technical viewpoint, Contentful, as a headless CMS, permits us to decide on which rendering technique we need to use. 

We’re at present finishing up the migration in a number of levels, or waves, to scale back the chance of issues which have a large-scale damaging influence. Throughout the first wave, we encountered a difficulty with our cookie consent, which led to a visibility lack of virtually 22% inside 5 days. On this article I will describe the issues we had been going through throughout this primary migration wave and the way we resolved them.

Organising the primary test-wave 

For the primary test-wave we selected 10 website positioning pages with excessive site visitors however low conversion charges. We established an infrastructure for reporting and monitoring these 10 pages: 

  • Rank-tracking for many related key phrases 

  • website positioning dashboard (DataStudio, Moz Professional,  SEMRush, Search Console, Google Analytics)

  • Common crawls 

After a complete planning and testing part, we migrated the primary 10 website positioning pages to the brand new CMS in December 2021. Though a number of challenges occurred in the course of the testing part (elevated loading instances, greater HTML Doc Object Mannequin, and so on.) we determined to go reside as we did not see large blocker and we wished emigrate the primary testwave earlier than christmas. 

First efficiency evaluate

Very enthusiastic about reaching step one of the migration, we took a have a look at the efficiency of the migrated pages on the following day. 

What we noticed subsequent actually did not please us. 

In a single day, the visibility of tracked key phrases for the migrated pages lowered from 62.35% to 53.59% — we misplaced 8.76% of visibility in in the future

Because of this steep drop in rankings, we performed one other in depth spherical of testing. Amongst different issues we examined for protection/ indexing points, if all meta tags had been included, structured information, inside hyperlinks, web page velocity and cell friendliness.

Second efficiency evaluate

All of the articles had a cache date after the migration and the content material was totally listed and being learn by Google. Furthermore, we might exclude a number of migration threat elements (change of URLs, content material, meta tags, format, and so on.) as sources of error, as there hasn’t been any adjustments.

Visibility of our tracked key phrases suffered one other drop to 40.60% over the following few days, making it a complete drop of virtually 22% inside 5 days. This was additionally clearly proven compared to the competitors of the tracked key phrases (right here “estimated site visitors”), however the visibility seemed analogous. 

Data from SEMRush, specified keyword set for tracked keywords of migrated pages

As different migration threat elements plus Google updates had been excluded as sources of errors, it undoubtedly needed to be a technical subject. An excessive amount of JavaScript, low Core Net Vitals scores, or a bigger, extra advanced Doc Object Mannequin (DOM) might all be potential causes. The DOM represents a web page as objects and nodes in order that programming languages like JavaScript can work together with the web page and alter for instance fashion, construction and content material.

Following the cookie crumbs

We needed to determine points as rapidly as doable and do fast bug-fixing and decrease extra damaging results and site visitors drops. We lastly bought the primary actual trace of which technical motive might be the trigger when one in every of our instruments confirmed us that the variety of pages with excessive exterior linking, in addition to the variety of pages with most content material measurement, went up. It will be important that pages do not exceed the utmost content material measurement as pages with a really great amount of physique content material is probably not totally listed. Concerning the excessive exterior linking it will be important that every one exterior hyperlinks are reliable and related for customers. It was suspicious that the variety of exterior hyperlinks went up similar to this.

Increase of URLs with high external linking (more than 10)
Increase of URLs which exceed the specified maximum content size (51.200 bytes)

Each metrics had been disproportionately excessive in comparison with the variety of pages we migrated. However why?

After checking which exterior hyperlinks had been added to the migrated pages, we noticed that Google was studying and indexing the cookie consent kind for all migrated pages. We carried out a web site search, checking for the content material of the cookie consent, and noticed our idea confirmed: 

A site search confirmed that the cookie consent was indexed by Google

This led to a number of issues: 

  1. There was tons of duplicated content material created for every web page attributable to indexing the cookie consent kind. 

  2. The content material measurement of the migrated pages drastically elevated. It is a drawback as pages with a really great amount of physique content material is probably not totally listed. 

  3. The variety of exterior outgoing hyperlinks drastically elevated. 

  4. Our snippets all of a sudden confirmed a date on the SERPs. This is able to counsel a weblog or information article, whereas most articles on Homeday are evergreen content material. As well as, because of the date showing, the meta description was minimize off. 

However why was this taking place? In accordance with our service supplier, Cookiebot, search engine crawlers entry web sites simulating a full consent. Therefore, they achieve entry to all content material and copy from the cookie consent banners aren’t listed by the crawler. 

So why wasn’t this the case for the migrated pages? We crawled and rendered the pages with totally different consumer brokers, however nonetheless could not discover a hint of the Cookiebot within the supply code. 

Investigating Google DOMs and looking for an answer

The migrated pages are rendered with dynamic information that comes from Contentful and plugins. The plugins comprise simply JavaScript code, and typically they arrive from a associate. One among these plugins was the cookie supervisor associate, which fetches the cookie consent HTML from exterior our code base. That’s the reason we did not discover a hint of the cookie consent HTML code within the HTML supply information within the first place. We did see a bigger DOM however traced that again to Nuxt’s default, extra advanced, bigger DOM. Nuxt is a JavaScript framework that we work with.

To validate that Google was studying the copy from the cookie consent banner, we used the URL inspection instrument of Google Search Console. We in contrast the DOM of a migrated web page with the DOM of a non-migrated web page. Throughout the DOM of a migrated web page, we lastly discovered the cookie consent content material:

Within the DOM of a migrated page we found the cookie consent content

One thing else that bought our consideration had been the JavaScript information loaded on our previous pages versus the information loaded on our migrated pages. Our web site has two scripts for the cookie consent banner, supplied by a third social gathering: one to indicate the banner and seize the consent (uc) and one which imports the banner content material (cd).

  • The one script loaded on our previous pages was uc.js, which is answerable for the cookie consent banner. It’s the one script we’d like in each web page to deal with consumer consent. It shows the cookie consent banner with out indexing the content material and saves the consumer’s resolution (in the event that they agree or disagree to the utilization of cookies).

  • For the migrated pages, other than uc.js, there was additionally a cd.js file loading. If we now have a web page, the place we need to present extra details about our cookies to the consumer and index the cookie information, then we now have to make use of the cd.js. We thought that each information are depending on one another, which isn’t appropriate. The uc.js can run alone. The cd.js file was the rationale why the content material of the cookie banner bought rendered and listed.

It took some time to seek out it as a result of we thought the second file was only a pre-requirement for the primary one. We decided that merely eradicating the loaded cd.js file can be the answer.

Efficiency evaluate after implementing the answer

The day we deleted the file, our key phrase visibility was at 41.70%, which was nonetheless 21% decrease than pre-migration. 

Nonetheless, the day after deleting the file, our visibility elevated to 50.77%, and the following day it was virtually again to regular at 60.11%. The estimated site visitors behaved equally. What a aid! 

Quickly after implementing the solution, the organic traffic went back to pre-migration levels


I can think about that many SEOs have handled tiny points like this. It appears trivial, however led to a major drop in visibility and site visitors in the course of the migration. This is the reason I counsel migrating in waves and blocking sufficient time for investigating technical errors earlier than and after the migration. Furthermore, protecting a detailed have a look at the location’s efficiency throughout the weeks after the migration is essential. These are undoubtedly my key takeaways from this migration wave. We simply accomplished the second migration wave to start with of Might 2022 and I can state that up to now no main bugs appeared. We’ll have two extra waves and full the migration hopefully efficiently by the tip of June 2022.

The efficiency of the migrated pages is nearly again to regular now, and we’ll proceed with the following wave. 


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