A browser and operating system (OS) compatibility system may include a user interface to select a first combination of a browser and OS for comparison to a second combination of a browser and OS. A download engine may capture source files for browsers for the first and second combinations. A parse engine may create Document Object Model (DOM) trees of objects of first and second website pages respectively for the browsers for the first and second combinations. A metric engine may read the DOM trees for attributes of the objects to capture metrics of the objects. An analysis metric engine may compare a metric of an object of the first website page to a metric of the same object of the second website page to determine a compatibility of the browser and the OS for the first combination to the browser and the OS for the second combination.