The first responsive testing tool on the list is right inside your Chrome browser. The same tool you use to inspect a site’s code also has a feature to test screen sizes and viewports. Right-click on any website and click ‘Inspect’. Once the inspect window opens, you’ll see the icon for devices next to the button named ‘Elements.’ When you click on the devices button, your screen shows the website you’re on at different breakpoints.
You can input a specific size or simply grab and drag the corner of the window to change the breakpoint manually. This is great for checking how your design is adapting to the different viewports.