Viewpo
The responsive testing tool that grades your site and shares results
Test your site at multiple viewports, get automated issue detection, and share professional reports. No install, no sign-up required.
What to look for in a responsive testing tool
Key criteria for choosing the right tool — and how Viewpo stacks up.
Multi-viewport comparison
Test at phone, tablet, laptop, and desktop sizes simultaneously — not one at a time.
Viewpo shows all viewports side-by-side with real screenshots.
Automated quality grading
A good responsive testing tool should tell you if your site passes — not just show you what it looks like.
Viewpo gives every audit an A-F grade based on automated responsive design checks.
API for automation
For CI/CD pipelines and AI coding agents, you need programmatic access — not just a web UI.
Viewpo's HTTP API returns structured JSON with screenshots, audit results, and grades.
Shareable reports
Results should be shareable with a link, not locked behind a login or a desktop app.
Every Viewpo audit has a permanent, shareable URL with OG preview cards.
Responsive testing tools: desktop apps vs web-based
Traditional responsive testing tools like Polypane, Responsively App, and Sizzy are desktop applications that require installation. They're powerful for developers who test responsiveness during development, with features like synced interactions and CSS debugging. Web-based tools like Viewpo take a different approach — paste any URL and get instant results without installing anything. The trade-off: less live-development tooling, but faster auditing and shareable results.
Why grading matters for responsive testing
Most responsive testing tools show you what your site looks like at different sizes — and stop there. You still need to manually spot issues. Viewpo goes further by running automated checks for overflow, touch targets, contrast, and accessibility at every viewport, then scoring the results from A (excellent) to F (failing). This turns subjective "does it look ok?" into objective "does it pass the audit?"
Frequently Asked Questions
Common questions about choosing a responsive testing tool.
A responsive testing tool helps you check how your website looks and functions at different screen sizes. Tools range from simple iframe viewers to full development browsers. The best responsive testing tools combine visual preview with automated issue detection.
Try the responsive testing tool that grades your site
Paste any URL and get real browser screenshots at multiple viewports with an A-F responsive design grade. Free, no install.
Free during beta. Plans from $19/mo at launch — early supporters get a lifetime discount.