How to update a Mac running macOS 8.5?

No Mac Pro or the similar-looking PowerMac G5 ever shipped with OS 8.5. No one here can "see" what kind of Mac you have, so please help us help you. It's not pretty when we have to guess!

If you cannot find the Model on the computer, at least post a photo. That's better than what we have now., which is nothing. Use the image insertion tool to place a picture into a response:

Images must be under about 5MB in size and in jpg or png format.

Mac OS 8.5 was for PowerPC-based Macs. No Mac Pro or MacBook anything ever ran it – since Apple only started using those model line names with the switch to Intel processors in 2006.

Anything old enough to run Mac OS 8.5 probably could not update beyond Mac OS 10.3.* (Leopard) or 10.4.* (Tiger). Such a Mac would be useless for running modern applications or for browsing the Web – although it might be useful as a computer museum exhibit, or as a platform for running games one purchased many, many years ago.

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If, by any chance, the OP meant 10.8.5, we would be taking about an Intel-based Mac. Then, the highest version of the OS that the OP could run might be anything from El Capitan to Big Sur, depending on the exact model. Current versions of Firefox and LibreOffice will run on Catalina and Big Sur.

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In any case, that Mac cannot be updated to one of the "most recent three" (Ventura, Sonoma, Sequoia).

what model year Mac Pro42 lb tower, or if a MacBook Pro, what model year AND screen size?