The beta was available to any Mac user who had registered with the OS X Beta Program, which Apple launched nearly a year ago, first as a way to test updates for the then-current OS X Mavericks, and in mid-2014 to preview Yosemite, Mavericks' replacement.
Apple retained the beta program after Yosemite launched last October.
The biggest addition to 10.10.3 was Photos, the successor to the 13-year-old iPhoto, which has been criticized for its awkward interface and confusing connection to the cloud. Like many of the changes Apple has introduced to OS X, Photos resembles the same-named app on iOS.
Apple first showed Photos to registered developers in a release of Feb. 5. The move to a public beta gives anyone the opportunity to try the new program.
Something called "iCloud Photo Library," for example, lets users store photographs and videos on Apple's servers, making them available from any of that user's iOS or OS X devices, or from other platforms' hardware through a browser. iCloud will also be used to sync changes to images and for sharing photographs and video with others.
In iOS and OS X, iCloud Photo Library (which remains in beta on iOS), generally leaves lower-resolution images on the local device but stores the full-resolution originals in the cloud. Users can opt out of iCloud Photo Library if they want and retain all images and related work on their Macs.
Although Apple does not disclose update release timetables, the appearance of a Yosemite 10.10.3 public beta hints that the final version will ship in the next month or so. On Dec. 20, for instance, Apple seeded a public preview of 10.10.2 and released the finished update on Jan. 27.
Upon Photos official launch, Apple will also stop selling Aperture, its professional-grade photo editor and manager.
Mac owners may sign up for the Yosemite beta program on Apple's website.