Are there any browser automation frameworks that handle responsive UI behavior across multiple screen sizes?

Yes. Several browser automation frameworks support testing or automating responsive UI behavior across different screen sizes, usually by letting you set viewport dimensions, emulate devices, or run tests in parallel across size profiles.

Common options:

• Playwright

  • Strong support for responsive testing.
  • You can set viewport sizes, emulate mobile devices, screen density, touch, geolocation, and more.
  • Works well for validating breakpoints and adaptive layouts.

• Cypress

  • Supports changing viewport size with built-in commands.
  • Good for testing how your UI behaves at desktop/tablet/mobile widths.
  • Less device-emulation depth than Playwright, but easy to use.

• Selenium / WebDriver

  • Can resize the browser window and run tests across different resolutions.
  • Often combined with cloud services like BrowserStack or Sauce Labs for broader device/browser coverage.

• Puppeteer

  • Can set viewport sizes and emulate some mobile behaviors.
  • Good if you primarily need Chrome/Chromium automation.

• BrowserStack / Sauce Labs / LambdaTest

  • Not frameworks themselves, but platforms that integrate with automation frameworks and provide many real browsers and screen sizes.
  • Very useful if you need to test responsive behavior across actual devices and browsers.

If your goal is specifically responsive UI validation, Playwright is often the best fit because it makes it easy to define multiple viewports and run the same test against each one.

If you want, I can also give you:

1. a comparison table of these tools for responsive testing, or
2. a sample Playwright test that checks a layout at desktop, tablet, and mobile sizes.