How Big Is My Browser is a simple free utility that instantly displays the current browser window's dimensions, useful for debugging layout issues and picking sensible default breakpoint sizes.
Free, no signup.
Designers and developers who need a one-second answer to "how big is my browser window right now" while debugging a responsive layout issue.
A genuinely single-purpose utility, useful specifically for quick, in-the-moment debugging rather than systematic responsive testing (for that, a tool like Polypane or Responsive Preview is a better fit).
A simple way to check the exact size of your browser window.
