Viewport Testing

What is Viewport Testing?

Viewport testing verifies that an application renders and functions correctly across the range of screen sizes users bring—phones, tablets, laptops, and wide desktops—so responsive layouts adapt properly and nothing breaks or overlaps at a given width. It catches issues that only appear at specific breakpoints, like a menu that collapses wrong or content that overflows on small screens. Playwright lets you configure viewport sizes per project, so a single recorded flow can be replayed across multiple viewports to confirm responsive behavior everywhere.