macOS for Mac mini server mid 2011

mac mini server mid 2011 currently running high sierra 10.13.6
running into many web sites including tidbits that i cannot log into with safari. running chrome here but that will not upgrade with this OS.
what can i do? is it possible to upgrade the device or must i replace it?

According to the MacTracker app, 10.13.6 is the highest level MacOS supported.

You can check the Open Core Legacy Patcher page to see if your computer could go higher but installation is not always easy:

It appears that your model is on the list.

The extended version of Firefox will support 10.3.16 for a while Firefox users on macOS 10.12, 10.13 and 10.14 moving to Extended Support Release | Firefox Help

As was already mentioned, you’re already running the latest version of macOS supported on this hardware.

WRT a supported web browser, Firefox’s ESR (Extended Support Release) is still compatible for a few more months. Their ESR release is based on Firefox 115 and should remain compatible with High Sierra until it gets bumped to version 128 on October 1st.

But yes, your computer is rapidly approaching the point where you will be forced to run old and therefore insecure web browsers. I’m rapidly approaching the same situation with my 2011 MacBook Air. I’ll be buying a new Air this summer (a refresh is expected in late March) because of that.

If you want to keep using your 2011 mini with Internet-connected software, I’d recommend researching how you may be able to install Linux on it. That should continue to have updates for quite some time. I know it’s not as easy as booting an installer CD, but I also know that it’s possible. Hopefully some web searching can find step-by-step instructions you can follow.

(I found one article from 2016, which might be a good starting point.)

Or just keep it around running High Sierra (or maybe erase and install something older) for compatibility with old apps after you upgrade your main Mac to something new (which will be incompatible with any 32-bit Intel apps). Just be very careful with any kind of Internet-connected apps, since they will be too old to be secure. But there’s no reason to avoid using it for apps that are running locally or only access network resources on your LAN.