Let’s unpack the different parts of Talos. At its heart, Talos is a simple test harness which creates a new Firefox profile, initializes the profile, calibrates the browser, runs a specified test, and finally reports a summary of the test results. The tests live inside the Talos repository and are one of two types: a single page which reports a single number (e.g., startup time via a web page’s onload handler) or a collection of pages that are cycled through to measure page load times. Internally, a Firefox extension is used to cycle the pages and collect information such as memory and page load time, to force garbage collection, and to test different browser modes. The original goal was to create as generic a harness as possible to allow the harness to perform all manner of testing and measure some collection of performance attributes as defined by the test itself.