“It looks fine on my screen” is how responsive bugs survive to production, because your screen is not your users’ screens. The tester surfaces the actual window, screen, and viewport dimensions and which breakpoint is active right now.
Watch the live window and screen dimensions plus the common breakpoint status as you resize. That instant read is what you need when matching a bug report that mentions a specific device.
Try it now: open the free tool, runs 100{b8b7921c843ac9e5edcbca134af59decad3ed340e0e3b2e6c286158f277affea} in your browser.
Bottom line: check the real viewport before you promise it looks fine.
Your turn: use the tool free here, no signup, nothing leaves your device.
How do you use Screen Resolution & Viewport Tester?
Open the Screen Resolution & Viewport Tester in your browser (Live window dimensions and aspect ratio). Type or paste your input, adjust the options, and copy the result. Everything runs locally on your device with no account and nothing stored, so the three steps below take seconds even for confidential work.
- Paste the data or snippet you want to process.
- Run the tool and watch the output update.
- Copy the result for use in your own code.
Try Screen Resolution & Viewport Tester free. It opens right in your browser.