Apple has begun testing Safari 10 with developers running the 2014 and 2015 editions of macOS, preparing for a fall release of the updated browser to users of Yosemite and El Capitan.
Safari 10 was introduced earlier this month as part of macOS Sierra, this year’s operating system upgrade.
Apple typically supports its newest browser on three editions of macOS: The latest version and its two predecessors. The now-current Safari 9, for example, receives updates, including security patches, on last year’s El Capitan, 2014’s Yosemite and 2013’s Mavericks.