The exact weight of Quality Score versus bid has not been revealed by any of the major search engines, and each company has stated that they reserve the right to continually adjust their ranking methodologies.
[5] The major search engines have each independently implemented efforts to maintain and improve the quality of ads listed on their sites.
While each search engine has released directional information on the factors most important to them, presumably in an effort to guide their advertisers towards making better ads, none has revealed their formulas in detail.
All three search engines have revealed that the relevance of the ad copy to the keyword is a factor in determining Quality Score.
In June 2008 Google revealed that landing page load time impacts Quality Score.
[8] Google has revealed that the account's performance in the geographical region where the ad will be shown impacts Quality Score.
[10] Google includes performance across devices so optimizing your ads and landing pages for mobile will boost your score overall.
[12] In order to achieve the highest quality score possible of 10/10, all those areas must be better than your competitors, particularly click-through rate (CTR).
[13] On May 15, 2017, Google announced improved reporting structure for quality score to gain deeper insight about keywords historical performance.
According to Google, "To save you time and help you make more informed decisions, we’re adding three new optional status columns to the Keywords tab for Exp.