Researchers and journalists have found many ways that advertisers can target—or exclude—particular groups of users seeing their ads on Facebook, comparatively little attention has been paid to the implications of the platform's ad delivery process, where the platform decides which users see which ads. In this talk I will show how we audit Facebook's delivery algorithms for potential gender and race discrimination using Facebook's own tools tools designed to assist advertisers. Following these methods we find that Facebook delivers different job ads to men and women as well as white and Black users, despite inclusive targeting. We also identify how Facebook contributes to creating opinion filter bubbles by steering political ads towards users who already agree with their content.