Responsive tester — Free CSS Tool

Responsive tester is an Astrina tool for CSS and front-end design. Previews at phone, tablet and desktop widths. It opens the page in a real browser on our render cluster, giving accurate results for JavaScript-heavy sites.

How to use Responsive tester

1. Enter the URL of the page.
2. Click "Run the check."
3. The page opens in a real browser on our servers — this takes 10–20 seconds.
4. Review the screenshot or metrics when the job completes.

What Responsive tester is used for

Professionals working in CSS and front-end design use this tool to save time and catch errors before they become problems. Common use cases:

• Auditing and quality checks in CSS and front-end design
• Validating or converting output before deploying
• Debugging issues quickly without switching between multiple tools
• Generating boilerplate output to speed up development

Key features

• Fast: server-side analysis in seconds
• Free for most use cases — no account required for the majority of checks
• Accurate: uses the same techniques as professional SEO and security scanners
• Privacy-friendly: we do not store the content we analyse beyond the session

About this tool

This is part of Astrina's suite of 21 CSS and front-end design tools. All tools are available at astrina.io/utilities.

Frequently asked questions

Try the Responsive tester now — no account required for most checks, and the result is ready in seconds.