Google has made the decision that on May 20th 2020, the Google Adsense ad balance tool will be retired.
The ad balance tool initially launched in 2017, empowered publishers of websites to have greater control of over the number of ads being shown on their website.
The tool allowed Adsense managers to undertake A/B tests, to either reduce the ad fill rate in order to weed out the less effective ads or increase it, showing more ads to greater numbers of users. Continued iterative testing with Ad fill allowed for constant improvement and adaptation to audience behaviour.
For instance, if you only wanted 50% of potential ads to be shown on your website, using the ad balance tool you could set the ad fill rate to 50%. This would mean that Google will only fill up to 50% of your ad units with the highest-paying ads.
According to Google, the decision to remove this feature was made off the back of feedback received from publishers. They claim that they remain focused on developing further blocking tools for low-quality ads, but for the time being ad slots will now be up to 100% populated as before this tool was introduced.