Tumblr uses information about what users post, like, search, and browse to decide which ads to show them. Rather than using complex behavioral prediction models, Tumblr's advertising approach is based on stated interests and content tags. Ads are also served through automated third-party advertising networks that handle placement in real time.

Blaze Pro, Tumblr's self-serve ad platform, targets users by interest categories and tags rather than through opaque predictive algorithms. Automattic's Head of Advertising has publicly positioned this as a deliberate choice against "black-box targeting algorithms" that rely on tracking technologies facing legal and technical challenges. Tumblr also serves programmatic ads through third-party partners including Nimbus, whose automated ad auction system handles real-time ad placement. A former Tumblr employee noted the platform's user data — built from post and engagement history — is relatively thin compared to rivals, leaving Tumblr more dependent on external programmatic providers.