The Google Publisher Tag (GPT) script is a robust JavaScript library provided by Google to facilitate the serving of ads from Google Ad Manager. It operates asynchronously, ensuring that ad loading does not impede the rendering of the rest of the web page content, thereby improving user experience and page performance. When integrated into a website, GPT creates ad slots (containers) on the page and then communicates with Google's ad servers to fetch relevant ad creatives based on publisher-defined targeting criteria, user characteristics, and contextual information. It supports various ad formats, including display ads, native ads, and video ads, and can handle complex ad setups like responsive ads that adapt to different screen sizes and environments. The script also manages impression tracking, click tracking, and viewability measurement, providing critical data for ad campaign performance analysis. It is designed to work efficiently with consent management platforms (CMPs) to ensure compliance with privacy regulations. GPT also supports advanced features such as Single Request Architecture (SRA), which allows all ad slots on a page to be requested in one call to the ad server, reducing latency and enabling competitive exclusions. Publishers can define granular targeting key-values for individual ad slots, implement ad refresh logic, and integrate with header bidding solutions to maximize ad revenue.