Apple has released a beta version of Safari 15, distinct from the Safari Technology Preview, for macOS Catalina, featuring the app's redesign that accompanies macOS Monterey.
The Safari 15 beta was first spotted by 9to5Mac, but contrary to reports that it is only available to download using the AppleSeed Program via an exclusive invite from Apple, the beta is in fact open to all users with a developer account.
Safari 15 is available in macOS Monterey, but users of the current release of macOS, macOS Big Sur, are able to explore the features of Safari 15 via the latest Safari Technology Preview, release 128. This new beta version, separate from the Monterey beta or the Safari Technology Preview, makes Safari 15 available for users of macOS Catalina.
Earlier versions of Safari 15 included a significant redesign that did away with the dedicated URL and search interface, instead allowing any individual tab to be used for navigation input. Tabs were also all arranged at the top of the display to minimize the space taken up at the top of a Safari window.
After a number of complaints about the new interface from users, macOS Monterey beta 3 made these design changes optional. Safari 15 also includes new features such as tab groups and a redesigned sidebar.
The Safari 15 beta and the Safari Technology Preview allow users of macOS Catalina and macOS Big Sur to try the new design and features without needing to update their entire Mac's OS to a beta version of macOS Monterey.
Nevertheless, 9to5Mac reports that some users are also being invited by Apple to join the AppleSeed program to try a pre-release version of Safari 15 and provide feedback.