Quick Summary
- Responsive testing tools check that your website works well on all screen sizes.
- Best overall: BrowserStack. Best free: Chrome DevTools and Responsively App. Best for SEO: PageSpeed Insights.
- New for 2026: AI visual testing (Applitools, Percy) and self healing tests (TestMu AI, Testsigma).
- Two old tools are gone: Google’s Mobile-Friendly Test and CrossBrowserTesting. This guide includes their replacements.
- Use free tools while you build, then test on real devices before you launch.
Most people visit websites on their phones. If your site looks good on a computer but breaks on a small screen, you lose visitors. Google also ranks the mobile version of your page first. So a responsive site is not optional anymore.
Responsive testing tools help you find layout problems before your visitors do. This guide lists the best ones for 2026. Every tool here is live and up to date. We also removed old tools that no longer work.
If you would rather leave it to experts, our responsive web design service takes care of all of this. If you want to test it yourself, here is what to use.
What Is New in 2026
Three things have changed in responsive testing this year.
AI visual testing. New tools like Applitools and Percy check your layout automatically. They spot real problems and ignore small changes that do not matter.
Self healing tests. Tools like TestMu AI and Testsigma let you write tests in plain English. When your site changes, the tests fix themselves. This saves a lot of time.
New devices. Foldable phones like the Galaxy Z Fold create new layout issues. You need real devices to catch these, not just emulators.
The simple approach: use free tools while you build, then use real devices and AI tools for final checks.
Quick Comparison
| Tool | Type | Real devices | AI | Price | Rating |
| Chrome DevTools | Free tool | No | No | Free | 4.5/5 |
| Responsively App | Dev browser | No | No | Free | 4.5/5 |
| Polypane | Dev browser | No | Some | Paid | 4.5/5 |
| Sizzy | Dev browser | No | No | Paid | 4/5 |
| Responsinator | Preview | No | No | Free | 4/5 |
| Responsive Design Checker | Preview | No | No | Free | 4/5 |
| Lighthouse / PageSpeed Insights | Audit | No | No | Free | 4.5/5 |
| BrowserStack | Cloud | Yes | Yes | Paid | 5/5 |
| TestMu AI (was LambdaTest) | Cloud | Yes | Yes | Freemium | 4.5/5 |
| Testsigma | Automation | Yes | Yes | Free and paid | 4.5/5 |
| BitBar | Cloud | Yes | No | From $39/mo | 4/5 |
| Applitools Eyes | AI visual | Yes | Yes | Paid | 4.5/5 |
| Percy | AI visual | Yes | Yes | Paid | 4.5/5 |
Free Tools for Daily Use
1. Chrome DevTools
Rating: 4.5/5
This is free and built into Chrome. Press Ctrl or Cmd, Shift, and M to open it. You can change the screen size and test different phones right away. It only simulates devices, so check important pages on real phones too.
Key features:
- Device mode to test many screen sizes
- Network throttling to test slow connections
- Live inspection of HTML and CSS
- Built in Lighthouse reports
2. Responsively App
Rating: 4.5/5
Responsively App is free and open source. It shows many devices at once. When you scroll or click on one, all of them do the same.
Key features:
- Free and open source
- Many devices shown side by side
- Mirrored scrolling and clicks
- One inspector for all screens
Try it: responsively.app
3. Polypane
Rating: 4.5/5
Polypane is built for responsive work. It shows several screen sizes at once and adds extra checks in one place. It is a paid tool, so it suits people who do this work every day.
Key features:
- Many synced screens at once
- Accessibility and WCAG checks
- Core Web Vitals monitoring
- Built in debugging tools
Try it: polypane.app
4. Sizzy
Rating: 4/5
Sizzy is a browser for developers. It shows many device sizes at once and updates them live as you edit your code. It is paid and works best while you are building.
Key features:
- Many devices in one window
- Synced scrolling across screens
- Live editing with instant updates
- Screenshot tools
Try it: sizzy.co
5. Responsinator
Rating: 4/5
Responsinator is for quick checks. Paste your URL and see your site on common phones and tablets. It needs no setup.
Key features:
- Free and simple
- Common phone and tablet views
- No sign up needed
- Instant preview
Try it: responsinator.com
6. Responsive Design Checker
Rating: 4/5
This tool is similar to Responsinator. Enter a URL and view your site on different devices. It shows how your site looks, not how it works, but it is quick.
Key features:
- Free to use
- Many device sizes
- No setup needed
- Fast visual check
Try it: responsivedesignchecker.com
7. Lighthouse and PageSpeed Insights
Rating: 4.5/5
This is Google’s official replacement for the old Mobile-Friendly Test. Run it on the mobile tab and you get a full report on your site.
Key features:
- Free from Google
- Scores speed, SEO, and accessibility
- Core Web Vitals data
- Runs in Chrome and in CI
Try it: pagespeed.web.dev
Cloud and Automation Tools
8. BrowserStack
Rating: 5/5
BrowserStack lets you test on real devices, over 3,500 of them. You get live testing, automation, and network testing. The price goes up as you run more tests, so it is best for teams.
Key features:
- 3,500+ real devices and browsers
- Live and automated testing
- Network condition testing
- AI agents and CI/CD support
Try it: browserstack.com
9. TestMu AI (was LambdaTest)
Rating: 4.5/5
LambdaTest changed its name to TestMu AI in January 2026. The platform, logins, and links are the same. You get thousands of browsers and devices plus an AI agent that writes and fixes tests.
Key features:
- Thousands of browsers and devices
- Real time and automated testing
- KaneAI agent for plain English tests
- CI/CD tools like Jenkins and CircleCI
Try it: testmuai.com
10. Testsigma
Rating: 4.5/5
Testsigma lets you write tests in plain English. It runs them across many browsers and devices and fixes broken tests on its own. It is a strong choice for automation without coding.
Key features:
- Write tests in plain English
- Cross browser and device testing
- Self healing tests
- Free and paid plans
Try it: testsigma.com
11. BitBar
Rating: 4/5
BitBar replaced the old CrossBrowserTesting. It offers real device and cross browser testing and works well with other SmartBear tools. Plans start around $39 a month.
Key features:
- Real device and cross browser testing
- Live and automated testing
- Works with TestComplete
- Local testing behind firewalls
Try it: smartbear.com/product/bitbar
AI Visual Testing Tools
These tools check your layout across many builds and devices. They use AI to find real problems and skip changes that do not matter.
12. Applitools Eyes
Rating: 4.5/5
Applitools compares your site before and after changes. It shows the real problems and ignores minor differences. It is best for large sites that change often.
Key features:
- Visual AI comparison
- Works across browsers and devices
- Filters out small rendering noise
- Works with Selenium, Cypress, and Playwright
Try it: applitools.com
13. Percy
Rating: 4.5/5
Percy takes screenshots on every code change and shows what looks different. It has an AI review feature that highlights only the important changes. It is part of BrowserStack.
Key features:
- Snapshots on every code change
- AI visual review agent
- Works across responsive screens
- Fits into your CI/CD pipeline
Try it: browserstack.com/percy
How to Choose the Right Tool
Pick a tool based on how you work.
If you are a developer, start with Chrome DevTools. Add Sizzy, Polypane, or Responsively App to see all screen sizes at once.
If you are in QA, use BrowserStack, TestMu AI, or Testsigma. Add Applitools or Percy for visual testing.
If you run an agency, cloud tools like BrowserStack and TestMu AI are easiest. You get many devices and no setup.
A simple stack for most teams:
- Build with Chrome DevTools and Lighthouse (free).
- Check breakpoints in Polypane or Sizzy.
- Test on real devices with BrowserStack or TestMu AI.
- Add Percy or Applitools for visual checks.
If your site is old and hard to fix, a website redesign may be the better choice.
Conclusion
Responsive testing is now a core part of building a website that ranks well and keeps visitors happy. The good news is that you do not need every tool on this list. Start with free tools like Chrome DevTools and Lighthouse while you build. Then test on real devices with BrowserStack or TestMu AI before you launch. If you want AI to catch layout problems for you, add Applitools or Percy.
Pick the tools that match how your team works, and check your list once a year, because these tools change fast. And if you would rather skip the testing and simply get a website that works on every screen, WebyKing can build it for you.
FAQs
What is the best responsive web design test tool online?
For a quick online check, use Responsinator or Responsive Design Checker. For a full report, use PageSpeed Insights. To test on real devices online, use BrowserStack or TestMu AI.
What is the best free responsive testing tool?
Chrome DevTools and Responsively App are the best free tools. Lighthouse and PageSpeed Insights are best for scoring your site. Responsinator is best for a quick look.
What replaced Google's Mobile-Friendly Test?
Google closed it in December 2023. Use PageSpeed Insights for a mobile report, Search Console to see how Google reads your page, and a tool like BrowserStack to check how it looks.
Which tool supports automated cross browser testing?
BrowserStack, TestMu AI, Testsigma, and BitBar all support it. Testsigma and TestMu AI also let you write tests in plain English.
What is the best AI tool for responsive testing in 2026?
For visual testing, use Applitools or Percy. For test writing and self healing, use TestMu AI or Testsigma.
How do I check if my site is responsive without real devices?
Use Chrome DevTools, Polypane, Sizzy, or Responsively App to test on your computer. Run Lighthouse for a score. But real devices are still best for final checks.
Is CrossBrowserTesting still available?
No. It closed on July 31, 2023. Use BitBar instead. SmartBear offers guides to move your old tests over.
