Best Practices for Ensuring Code Compatibility with Users’ Browsers

How are you all making sure that the code/features you are launching will work with your user base? As a Product Manager, Designer and Developer, I am always wondering, after I design something, and I need to code it… what Can I Use? What CSS can I use to make this work? The answer to that question largely depends on what browsers people are using to access my website or app. For example, I want to let content authors use any size photo they have access to but make sure the photo they use is cropped and fills the entire photo space. That is easy to do with modern CSS, specifically aspect-ratio … but some browsers still don’t support modern CSS. My process is to go to Can I Use (https://caniuse.com/) and search for the CSS I want to use to solve the current problem. Now I can see which browsers support my solution. With that information in hand, I now need to know if any of the browsers that do not support the solution are accessing my website/app and, if so, how many. This is the dashboard I am using today on a newer project. Curious if anyone has found a better way in Mixpanel?