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A Responsive Viewer alternative that finds the bugs
Responsive Viewer is a free Chrome extension that shows the page you are on at several screen sizes in one view, so developers can watch layouts while they work. It loads the page in frames, which some sites and logins don’t allow, and the looking is up to you. UICheck opens the page at each size in a real browser, measures it and lists what broke, with the element and the fix.
Side by side
UICheckResponsive Viewer
Responsive ViewerWhat it isUICheck: Automatic responsive and layout QA for any URLResponsive Viewer: Chrome extension showing several screen sizes at once
InstallUICheck: Nothing, runs in the cloudResponsive Viewer: Chrome extension
Finds bugsUICheck: Yes, automaticallyResponsive Viewer: No, you look for them
Safari and FirefoxUICheck: Yes (Lens and Prism)Responsive Viewer: Chrome only
Whole siteUICheck: Up to 15 or 250 pages per checkResponsive Viewer: The page you have open
Report for clientsUICheck: Share link without login, PDF and ExcelResponsive Viewer: Screenshots you take
Based on public information, checked October 2026. Something changed? Tell us and we’ll update it.
Choose Responsive Viewer if
- You want several sizes open while you write CSS, for free
Choose UICheck if
- You want the problems found and listed for you
- You need Safari and Firefox, or the whole site
- Someone who doesn’t write code needs to read the result
Or use both
Keep the extension for development; run UICheck on staging before each launch.
Also compare
Try UICheck next to Responsive Viewer
Free account, 5 checks a day, no card. Paste a URL and see what it finds in about a minute.