The `last baseline` keyword for alignment properties (align-content, align-items, and align-self) is recognized by the parser but for both flex and grid layout, there are FIXMEs for actually supporting it: https://trac.webkit.org/browser/webkit/trunk/Source/WebCore/rendering/RenderFlexibleBox.cpp?rev=287742#L1679 https://trac.webkit.org/browser/webkit/trunk/Source/WebCore/rendering/RenderGrid.cpp?rev=287742#L1437 Support for this in other browsers can be seen here: https://developer.mozilla.org/en-US/docs/Web/CSS/align-content#browser_compatibility https://developer.mozilla.org/en-US/docs/Web/CSS/align-items#browser_compatibility https://developer.mozilla.org/en-US/docs/Web/CSS/align-self#browser_compatibility Note that the data is a bit messy and also wrong in places, which is why I started looking into support across browsers and filed this bug. https://crbug.com/885175 is the Chromium bug for this.
<rdar://problem/87640022>