Apple has released Safari Technology Preview 152. The upgrade includes bug fixes and performance improvements for Web Inspector, CSS, Accessibility, Rendering, JavaScript, and Web API.
Safari Technology Preview offers a sneak peek at upcoming web technologies in macOS and iOS. You can experiment with these technologies in your websites and extensions. 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.