User Signal Service (USS) is a centralized online platform that supplies comprehensive data on user actions and behaviors on Twitter. This information encompasses both explicit signals, such as favoriting, retweeting, and replying, as well as implicit signals, including tweet clicks, video views, profile visits, and more.
To ensure consistency and accuracy, USS gathers these signals from various underlying datasets and online services, processing them into uniform formats. These standardized source signals are then utilized in candidate retrieval and machine learning features for ranking stages.