The importance of web application performance has dramatically increased in the past few years, since users expect your webpage to be displayed within milliseconds across all devices. So checking how fast your website actually renders and how performant it is overall not only on desktop devices but more importantly on mobile, is super important.
The first thing that probably pops up if you are searching for performance check is Google’s Page-Speed Insights. The last time I ran my web application through Page-Speed Analysis, I saw that they use a new engine called “Lighthouse”, which is actually integrated in Google’s developer tools.
I, of course, tried it out and found the overview of the analysis pretty cool.
So, if you open Chrome developer tools and go to “Audits” tab, you can choose what exactly you want to analyze and on what device. It also simulates connection speed and offline mode to check your app's behavior:
When you click “Run audits”, you get a pretty well structured result overview with suggestions to improve, similar to Page-Speed:
From this point, I recommend you just pick some of the suggestions that will result in the most performance improvement and implement them one at a time. I must mention though, that some improvements on the list are unrealistic since they relate to the third party libraries, so I guess instead of aiming for a 100% score, just try to make improvements only where it makes sense.