It’s not all good news coming out of WWDC this year:
.safariextz-style Safari Extensions installed from the Safari Extensions Gallery is deprecated with Safari 12 on macOS. Submissions to the Safari Extensions Gallery will no longer be accepted after December 2018. Developers are encouraged to transition to Safari App Extensions.
That’s not just for users, either — all old-style Safari extensions are deprecated:
Support for developer-signed
.safariextzSafari Extensions in Safari 12 on macOS has been removed. They no longer appear in Safari preferences and cannot be enabled. On first launch users will receive a warning notification and these extension will not load.
Well, that’s a bummer — I still use a handful of older-style extensions that have no modern equivalents that are quite as simple. JS Blacklist is one of my favourite pieces of software because it allows me to block problematic scripts rather than ads more generally. There are content blockers available on the Mac App Store, but nothing quite as refined. But this isn’t a surprise; the writing has been on the wall for old-style extensions ever since Apple’s developer tiers were changed three years ago.