For some time now, Google has been publicly encouraging website owners to transition to HTTPS, a more secure version of the ubiquitous HTTP protocol that powers the web. You can identify websites that use HTTPS with the padlock symbol in the address bar:

In August 2014, Google went one step further and used their considerable influence as the world’s most popular search engine to entice website owners to make the switch, by announcing an SEO ranking boost for sites that use HTTPS. Although the ranking boost is small, Google suggests it will increase with time.

Rome2rio has supported HTTPS for some time now. We use it for parts of the site related to user accounts, passwords, and ticket purchases. However, in July last year, we decided to take the plunge and force all users to view the entire site through HTTPS. Technically the project went smoothly, but after ramping the change to 100%, we noticed a significant drop in our Google advertising revenue.

Our research quickly revealed that other website owners had experienced that same thing. We learnt that not all advertisers that place bids through the Google ads system support HTTPS, resulting in fewer ad impression bids and lower overall ad revenue. We learnt that many website owners had transitioned back to HTTP for this reason. We concluded the revenue drop was too large to justify the switch to HTTPS, so we also made the switch back.

In January, we decided to re-visit the HTTPS question. This time, we properly measured the potential impact with an A/B split test. We redirected visitors to HTTPS for 5% of pages and measured the change in ad revenue. Our conclusion; ad revenue was 7% lower for the HTTPS pages.

We dug down further and examined the impact on ad revenue for each of Rome2rio’s top advertisers:

The data illustrates that the overall 7% drop in revenue appears largely due to a handful of advertisers where revenue drops by more than 40%.

Google is working hard to transition all advertisers to HTTPS, and we hope to see this 7% figure decrease when we next repeat this A/B test in 6 to 12 months.