How to optimize manual testing of websites in mobile browsers

Often during manual testing of web sites on mobile devices you can face to the necessity to run JavaScript code or set some cookies, view page source etc., in other words somehow interact with web development tools which are available in desktop browsers by F12. Moreover, there are a lot of different screen resolutions on mobile devices. All this creates some difficulties and takes precious time for testing. Fortunately, there are many solutions for these problems, ranging from simple to complex and those which require specialized knowledge. In my report I will tell about the tools that have already been used in work.