Quality index is a measure of the relevancy of your ad compared to ads that it competes with. It is displayed as one to five bars, where more bars means higher quality. Quality index reflects your ad's ability to meet the needs of users by looking at how relevant your ad is to each keyword and also its click-through rate relative to its position and other ads displayed at the same time. Your ad's quality index also impacts how much you need to bid and the position in which your ad appears—in some instances, ads with a higher quality index may require a lower bid and/or receive better placement on the results page.