Google Publisher Tag (GPT) is a client-side JavaScript library that facilitates the request and rendering of advertisements from Google Ad Manager on publisher websites. It allows publishers to define specific ad slots on their pages and provides granular control over ad serving, targeting, and display. The script operates asynchronously, meaning it does not block the loading of other page content, which improves page performance. GPT communicates with Google's ad servers to fetch relevant ad creatives based on defined criteria, user characteristics, and consent preferences, ensuring ads are displayed efficiently and contextually. It handles the lifecycle of ad display, including impression tracking, click-through measurement, and refreshing ads, all while adhering to various ad policies and technical specifications. The library is designed to be highly flexible, supporting responsive ad units that adapt to different screen sizes and various ad formats, including display, video, and native ads. It integrates with consent management platforms (CMPs) to help publishers comply with privacy regulations by respecting user consent choices for personalized advertising.