Question 1

How does the responsive design tester work?

Accepted Answer

The tool loads any URL inside an iframe at different viewport sizes, simulating how the website would appear on various devices. You can choose preset device sizes or enter custom dimensions.

Question 2

Why can't I see some websites in the tester?

Accepted Answer

Some websites block loading inside iframes using X-Frame-Options or Content-Security-Policy headers. This is a security feature. Sites like Google, Facebook, and many banking sites block iframe embedding.

Question 3

What devices can I test on?

Accepted Answer

The tool includes presets for iPhone SE, iPhone 14, iPhone 14 Pro Max, iPad, iPad Pro, MacBook Air, Desktop 1080p, Desktop 1440p, and 4K displays. You can also enter any custom width and height.

Responsive Design Tester

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NexTool on GitHub