Mac OS High Sierra was released back in 2017, but now, in 2021, it is officially unsupported by Apple. This means that the software will no longer receive any updates, including feature updates. Apple typically stops feature updates once the next version of OS comes out, so the one that came out after High Sierra was still receiving updates and it was still supported, but it wasn’t getting any new features because they were focusing on the next generation or the next release on Mac OS. However, High Sierra received security updates, and that’s what Apple does for all of their OS’s. They continue to release security updates until they decide to just stop.
Now that High Sierra is unsupported, the main problem with using it in 2021 is the lack of security updates. If any security-related issues arise, then people who use High Sierra are going to be vulnerable to it, and Apple will not update this anymore to fix it. That is, of course, the biggest risk with using it today. However, it doesn’t necessarily mean that you shouldn’t be using it in 2021. You can still use it, but you’re probably going to want to just be extremely careful when you’re browsing the web and things. You want to make sure you have good protection in place because you never know what is laying out there. There are exploits in every OS, even the current ones, the old ones, it doesn’t matter how old they are. There are exploits in there that people just haven’t found yet, and if somebody finds one and you’re still using an old OS, well, you’re kind of on your own. You just better hope your defenses are good to go.
As far as using it today, the lack of security updates is the biggest concern, but if you get a good browser, like Safari, which is pretty good with the Google Safe Browsing feature, it’s usually pretty good. There are also some other browsers you can get to make it more secure. You might want to consider installing some antivirus software or maybe just being careful. That’s really all you can do as far as using it.
The design of High Sierra is extremely familiar to what we have today. Obviously, Big Sur looks different now, but if you’re still on Catalina, for example, this is extremely similar. All the icons are the same, and all that stuff. Basically, if you sign into your iCloud account, you’re going to be available to access all the main new things that are in iCloud, so you shouldn’t have any problems with your Apple ID or anything. All these apps are basically the same. There’s really not much difference. High Sierra was updated to the Apple File System, modern video and coding, and different things like that, so again, it’s up to date in those regards too.
In conclusion, High Sierra is officially unsupported by Apple, so you want to be extremely careful when you’re browsing the web and things. But if you still want to use it, all the apps are going to work like the modern ones on Big Sur or Catalina, so you should have no problems. You can get the latest version of pretty much any app with no issues as well. Just remember to be cautious and watch out for possible exploits, and if you see one of those come up, you definitely want to quit using this asap.