Whether your website is optimized for certain browsers or versions or not, it is always a good idea to warn your visitors when they use versions with which the browsing experience will not be complete .
WordPress warns internally of the use of obsolete browsers but what about the visitors ?. Well for that there is a fantastic plugin called Advanced browser check .
Once activated you can configure the messages to be displayed and choose on which browsers and versions the warning will be displayed if you use old or obsolete versions. . The browsers it detects are Firefox, Chrome, Safari, Opera and Internet Explorer.
Once adjusted, if the visitor uses any of the browsers or versions of them that you have defined as obsolete, a pop-up window will appear where the notice you have determined as well as links to the official websites of each browser will be displayed.
Of course, this does not mean that you should not use a WordPress theme that is compatible with most browsers, but it is a good tactic in order to avoid losing visits and interaction on your website due to the fact that users use obsolete browsers.