When a Reading System renders a Synthetic Spread, the default behavior is to populate the spread by rendering the next EPUB Content Document in the next available unpopulated viewport, where the next
available viewport is determined by the given page progression direction or by local declarations within Content Documents.
Apple designed the Safari Technology Preview to test features that may be introduced into future release versions of Safari.Safari Technology Preview release 20 includes bug fixes and updates for Visual
Viewport, Touch Bar, JavaScript, Web API, Security, CSS, Pointer Lock, Web Inspector, WebCrypto API, and more.The Safari Technology Preview update is
available through the Software Update mechanism in the Mac App Store to anyone who has downloaded the browser.