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It is common practice when there are performance problems or want get a higher PageSpeed score, rely on CloudFlare in order to have a CDN with interesting JS and CSS minification functions, as well as image compressions that make the page less heavy and can also allow you to satisfy some of the best practices recommended by Google in order to obtain a best score on PageSpeed tests.
Cloudflare, Inc. is an American company that deals with content delivery networks, internet security services and distributed DNS services, which are placed between the visitors of a site and the hosting providers of Cloudflare users, acting as a reverse proxy server for websites.
Among other interesting features, that of WAF (Web Application Firewall), that of DDOS mitigation, GeoIP filtering, as well as DNS service.
It is a Big Company with clients such as Uber, OKCupid, Fitbit, Hubspot, Gyazo and many many others. In short, something really great and notable leader in its sector.
Offering a free plan suitable for most low / medium traffic sites, it is now common to see it used intensively even by sites that actually do not need it and could solve some speed problems directly on the server and / or application side.
Among other things it must be said that by default CloudFlare keeps a bad bots filtering feature enabled in order to reduce the number of malicious bots and crawlers hitting your site automatically.
According to a survey carried out in 2016 by Encapsulate (Imperva), a note and very valid alternative to Cloudflare with more or less similar functions, the traffic of bad bots would impact for about 30% of the entire web traffic, in other words, 30% of the traffic is produced by malicious bots, and about as many from good and legitimate Bots. Here you can read the report in full: https://www.incapsula.com/blog/bot-traffic-report-2016.html
What happens if we block the Bad Bots?
An answer full of common sense and logic could be that we will have less useless traffic on our site, less consumption of bandwidth, of resources and therefore obtain a greater degree of security.
Most likely it is a correct answer or probably so, since in fact it would be really difficult to understand what could be the usefulness of having malicious or malicious bots that roam freely on our site to make requests for pages for who knows what shady and mysterious reasons.
However, one thing is certain, if as we have seen before it is true that 30% of the visits are generated by malicious Bots, blocking the Bots will actually mean blocking even 30% of traffic on our site.
What about Google Adsense?
We agree at least in part, but Google AdSense should be left aside only if the activation of CloudFlare did not lead to a lowering of RPM and therefore monetization.
A strange (un) fortuitous event.
Some time ago we decided together with the CEO of an editorial network operating in various sectors to enable CloudFlare on all sites to optimize and improve the use of content and the delivery of images. Although we already had the usual optimized stack with Varnish and Memcache with NGINX and http / 2 in production, we wanted to try to push it further to see how the system could react. From the point of view of navigation, slight improvements, however appreciable, on the monetization side instead a drama. From the day after the RPM had decreased significantly and persisted for about the whole month, until we decided to delete CloudFlare and return to how we originally were. After a few days, the monetization situation normally resumed the optimal initial values that persisted for about a month, until we again decided to re-enter CloudFlare.
Not even to do it on purpose, same situation as before, RPM halved although the site was significantly faster and extremely fluid navigation. Why was not clear, there was no signal or motivation that could justify a lowering of revenue in that way.
We could not continue like this, therefore we have deactivated CloudFlare again and as if by magic, the usual optimal RPMs are back.
A pure chance?
The way things went, it cannot be said that it was a coincidence, especially if we consider that completely different sites were involved, both for the topics covered and for the contents, structure and peculiarities that made 5 individual sites completely different albeit from the same owner.
Searching for the keywords on Google: Cloudflare AdSense RPM you can find numerous posts from users who have stumbled upon the same problem as ours though CloudFlare itself claims that it does not negatively impact AdSense.
However, there are too many similar situations that are somehow atomically linked, as CloudFlare is enabled, AdSense revenue plummets.
Is there a causal link between cause and effect or are there other types of problems that you want to attribute to CloudFlare? Are they just singular cases due to some Cloudflare problem or more likely to some Google Adsense problem? With what logic? With what criterion? Because ?
Not being able to give useful answers due to insufficient evidence or a minimum of logical explanation about it, we will limit ourselves only to asking the right questions, hoping to do something useful to all those who decide to enable CloudFlare. Be cautious in noticing any changes in the monetization of the page and if you notice unexplained changes as happened to us, do not hesitate to enable / disable the cache in order to be able to replicate the problem and attribute the cause to it. If you want performance without affecting AdSense in any way, you can contact us.
Update as of 1 July 2019 : Having evaluated in the last month of June a correct behavior of CloudFlare without any lowering of the RPM with different advertising circuits, to be fair we would like to specify that what is written in this article concerning the decrease in RPM yield is no longer correct and valid. The reader is invited to independently assess any performance discrepancies.