295730 2025-07-10 11:57:13 -0700 REGRESSION (macOS 26): A large border-radius can cause shadows with a non-zero spread to render incorrectly 2025-07-10 15:19:19 -0700 1 1 1 Unclassified WebKit Layout and Rendering Safari 26 Mac (Apple Silicon) macOS 26 RESOLVED DUPLICATE 295213 InRadar P2 Normal --- 1 jordan webkit-unassigned bfulgham simon.fraser webkit-bug-importer zalan oldest_to_newest 2129067 0 475866 jordan 2025-07-10 11:57:13 -0700 Created attachment 475866 An HTML file that showcases the buggy shadow behavior In macOS 26 (I tested beta 3) Safari and Safari Tech Preview can incorrectly render box shadows when the border-radius is large enough and there is a non-zero spread value. For example, a spread of `1px` with a radius >= 16,781,246px draws the shadow incorrectly. Likewise, for a spread of `-1px`, a radius of `>= 16,781,379px` draws the shadow incorrectly. The following HTML can be used to reproduce the issue. For the negative spreads you shouldn't be able to see anything and the positive spreads should produce a slight border around the circle. Instead a black square inset/outset by the spread value is drawn behind the element in all four cases. ```html <div style=" width: 8rem; height: 8rem; box-shadow: 0 0 0 -1px #000; border-radius: 16781379px; " ></div> <div style=" width: 8rem; height: 8rem; box-shadow: 0 0 0 -1px #000; border-radius: calc(infinity * 1px); " ></div> <div style=" width: 8rem; height: 8rem; box-shadow: 0 0 0 1px #000; border-radius: 16781246px; " ></div> <div style=" width: 8rem; height: 8rem; box-shadow: 0 0 0 1px #000; border-radius: calc(infinity * 1px); " ></div> ``` Notes: 1. I am testing in a VM so it's possible that the actual values are environment depdendent and might be slightly different. 2. Using `calc(infinity * 1px)` produces a much larger value and as such is also affected by this bug. 3. The other values of the box shadow do affect the rendering but it's still bugged — just with a different final appearance. e.g. Giving the shadow a radius causes a blur to appear but applied to an incorrectly sized "bounding box". 4. iOS 26 (I tested beta 3) is also affected. 5. Safari and STP on macOS Sequoia are **NOT** affected. 2129129 1 webkit-bug-importer 2025-07-10 14:59:45 -0700 <rdar://problem/155561314> 2129140 2 simon.fraser 2025-07-10 15:19:19 -0700 *** This bug has been marked as a duplicate of bug 295213 *** 475866 2025-07-10 11:57:13 -0700 2025-07-10 11:57:13 -0700 An HTML file that showcases the buggy shadow behavior buggy-shadows.html text/html 508 jordan PGRpdgogIHN0eWxlPSIKICAgIHdpZHRoOiA4cmVtOyBoZWlnaHQ6IDhyZW07CiAgICBib3gtc2hh ZG93OiAwIDAgMCAtMXB4ICMwMDA7CiAgICBib3JkZXItcmFkaXVzOiAxNjc4MTM3OXB4OwogICIK PjwvZGl2PgoKPGRpdgogIHN0eWxlPSIKICAgIHdpZHRoOiA4cmVtOyBoZWlnaHQ6IDhyZW07CiAg ICBib3gtc2hhZG93OiAwIDAgMCAtMXB4ICMwMDA7CiAgICBib3JkZXItcmFkaXVzOiBjYWxjKGlu ZmluaXR5ICogMXB4KTsKICAiCj48L2Rpdj4KCjxkaXYKICBzdHlsZT0iCiAgICB3aWR0aDogOHJl bTsgaGVpZ2h0OiA4cmVtOwogICAgYm94LXNoYWRvdzogMCAwIDAgMXB4ICMwMDA7CiAgICBib3Jk ZXItcmFkaXVzOiAxNjc4MTI0NnB4OwogICIKPjwvZGl2PgoKPGRpdgogIHN0eWxlPSIKICAgIHdp ZHRoOiA4cmVtOyBoZWlnaHQ6IDhyZW07CiAgICBib3gtc2hhZG93OiAwIDAgMCAxcHggIzAwMDsK ICAgIGJvcmRlci1yYWRpdXM6IGNhbGMoaW5maW5pdHkgKiAxcHgpOwogICIKPjwvZGl2Pg==