A Google PageSpeed developer optimizes the performance of web pages, making them faster and more efficient. They utilize Google's PageSpeed Insights tool to analyze the content of a web page, identify issues slowing it down, and provide suggestions to make it faster. Their tasks involve reducing server response time, leveraging browser caching, enabling compression, minifying CSS, JavaScript, and HTML. They also optimize images and prioritize visible content. They work closely with web developers and designers to implement these changes, enhancing user experience, improving SEO rankings, and potentially increasing conversion rates.