Clear all of your history from the Safari 11 application menu. From Safari Preferences : Advanced : Show developer menu. Quit Safari. Press and hold the shift key while launching Safari 11 again. Press option+command+E to clear your browser cache. Turn off your extensions, and under Safari Help menu, list your plug-ins, and ensure they are current versions with Safari 11 compatibility.
The first step to updating your Safari browser is checking if your Mac actually has any available system updates. If you have macOS Mojave or later, upgrades will come via your System Preferences. The new Safari Technology Preview update is available for macOS Catalina and macOS Big Sur, the newest version of the Mac operating system that's set to be released this fall.
Evaluate if Safari 11 has improved performance. Try and live with it.
Apple does not provide separate downloads of Safari browsers. NOTE: If you have stayed current with the Security Updates below, you might skip everything listed, and just install the Security Update 2017-003 to see if it will overwrite Safari 11 with Safari 10.1.2. Otherwise, you are looking at an ordeal.
Download and install any that have not been applied already, but particularly 2017-003 because it contains Safari 10.1.2:
Sep 23, 2017 3:03 PM
Safari is the best way to see the sites on iPhone, iPad, and Mac. Safari Technology Preview gives you an early look at upcoming web technologies in macOS and iOS. Get the latest layout technologies, visual effects, developer tools, and more, so you can provide input on how they are implemented and deliver a best-in-class user experience on all Apple devices.
Preview the latest web technologies. Get a preview of the latest advances in Safari web technologies, including HTML, JavaScript, and CSS. Safari Technology Preview includes the most recent version of WebKit, the rendering engine that powers Safari.
Easy to update. You can update Safari Technology Preview right from the Mac App Store. Updates occur every few weeks and include the most recent version of WebKit.
Access powerful developer tools. Use the latest version of the powerful Web Inspector and Responsive Design Mode to modify, debug, and optimize your websites.
Safari - Official Apple Support
Provide feedback. Use Feedback Assistant to send feedback directly to Apple about issues and enhancement requests. Simply select Report an Issue from the Help menu in Safari Technology Preview.
Run side-by-side with Safari. Safari Technology Preview is a standalone app that works side-by-side with the current version of Safari, so you can continue to use and reference the current release.
Surf seamlessly with iCloud. Safari Technology Preview works with iCloud, so you can access your latest Safari Favorites, bookmarks, and Reading List.
Current Mac Safari Version
Keep current. The WebKit blog keeps you up-to-date on the latest developments in HTML, JavaScript, and CSS.