Page Performance Test is a Firefox add-on designed for web developers looking to measure the timing performance of any web page using Web APIs. This tool allows users to assess page load times across various metrics, including network, server, and browser performance. With the ability to save test results directly to the file system, developers can easily track and compare performance over time, enhancing their ability to optimize web applications effectively.

The add-on features an accurate chart that displays load times for each test, along with a convenient 'Save Result' button that timestamps the results for future reference. The latest update introduces a WebExtension icon that opens a popup for quick access to site performance data, leveraging the Web Performance API. Additionally, users can activate performance test devtools, making it a versatile tool for comprehensive web development.