Developers today don't have a reliable metric that correlates with their user's visual rendering experience. Existing metrics such as First Paint and First Contentful Paint focus on initial rendering, but don't take into account the importance of the painted content. Therefore, these metrics may…
Many websites suffer from layout instability - DOM elements shifting around due to content loading asynchronously.
This is the official repository for the performance-testing code that runs at webpagetest.org.