1. A method comprising: building a test for a web application; running the test using different browser/operating system combinations to capture screenshots and corresponding metadata for the different browser/operating system combinations; receiving a modification to a header during the running of the test, the modification adjusting performance of a server when rendering a screenshot; receiving, from a user device of a user, parameters indicating the different browser/operating system combinations for a visual comparison of the screenshots of a state for the different browser/operating system combinations; based on the different browser/operating system combinations indicated by the parameters, retrieving the screenshots along with the corresponding metadata for each indicated browser/operating system combination; and causing, using a processor of a machine, a user interface that visually compares at least two retrieved screenshots to be provided to the user device, the user interface including a display of the corresponding metadata for the at least two retrieved screenshots.