watchOS 9.5.1 is a 91.8MB update that Apple says is focused on bug fixes and improvements for Apple Watch. Apple does not list any security updates for this release.
The update is available either through the Settings app on Apple Watch or the Watch app on iPhone. Apple released watchOS 9.5, the previous version, earlier this month with the addition of a new Pride watch face for 2023.
The bigger watchOS update in the pipeline, of course, is watchOS 10. Apple will unveil the next major version of watchOS on Monday as it kicks off WWDC 2023. The Worldwide Developer Conference starts with a keynote address on June 5. watchOS 10 is expected to be a significant update for Apple Watch with a focus on widgets.
Early adopters should expect to see the first beta versions of watchOS 10 starting Monday. The final release will likely be released in September.