This release includes new features that will be shipping in Safari 12 later this year, including icons in tabs and automatic strong passwords.
One thing of note for web designers is that, after enabling icon tabs in the app’s settings, it looks like the browser defaults to using the website’s “mask-icon” for this feature. These icons were previously only used for pinned tabs and are limited to a single color.
But if you remove your website’s mask-icon entirely, Safari will fallback to displaying the site’s full color favicon instead. And there doesn’t appear to be any downside to removing a site’s mask-icon because this new version of Safari will display favicons for pinned tabs as well.