Cobriums Free Tool
Responsive Website Tester
Check how your website looks across mobile, tablet and desktop screen sizes from one simple workspace.
Loading website…
375 × 667 px
The preview uses an iframe. Some websites block embedded previews for security reasons.
Responsive Website Tester FAQ
Everything you need to know about testing responsive layouts.
| What is a Responsive Website Tester? | It lets you preview a website at different viewport sizes commonly used by phones, tablets, laptops and desktop screens. |
|---|---|
| How do I test my website? | Enter a complete website URL, choose a device size, and click Test Website. The selected viewport is displayed inside the tester. |
| Which screen sizes are available? | The tester includes common mobile, tablet and desktop viewport presets and also supports custom width and height values. |
| Can I test a website on a phone? | Yes. You can preview common mobile widths such as 320px, 375px and 390px by using the custom viewport option or device presets. |
| Can I test tablet sizes? | Yes. Common tablet viewports including 768px and 820px can be tested using the preset or custom dimensions. |
| Can I create a custom viewport? | Yes. Choose Custom and enter the width and height you want to test. |
| Why will some websites not appear in the preview? | Some websites use security policies such as X-Frame-Options or Content-Security-Policy that prevent them from being displayed inside an iframe. |
| Can I open the website normally? | Yes. Use Open in New Tab to visit the website directly when embedded preview is unavailable or when you want to inspect the live page normally. |
| Does this tool change my website? | No. The tester only loads the URL for preview and does not modify your website or its files. |
| Is the Responsive Website Tester free? | Yes. The Cobriums Responsive Website Tester is free to use. |
Have another problem to solve?
Explore more free Cobriums tools designed to make everyday tasks faster and simpler.
Free browser tool · No account required