150445 2015-10-22 07:37:26 -0700 Flexbox - flex direction column slow layout performance 2025-03-04 21:08:37 -0800 1 1 1 Unclassified WebKit Layout and Rendering Safari 9 Mac OS X 10.10 RESOLVED DUPLICATE 168657 https://bugs.webkit.org/show_bug.cgi?id=289072 InRadar P2 Major --- 1 scottbobertson webkit-unassigned beidson bernd.helzer eoconnor hyatt jonlee l1657572 ljharb mike.sherov mozilla mrflix rik simon.fraser webkit-bug-importer zalan oldest_to_newest 1135681 0 scottbobertson 2015-10-22 07:37:26 -0700 Nested divs with 'display: flex' and 'flex-direction: column' have very slow performance in Safari. At a depth of 18 divs with these CSS properties Safari takes a total of 6578ms to layout and paint the divs this time grows exponentially as the depth of divs increases. This same test performed on Chrome or Firefox takes 2ms. Here is a demo of the problem. (open the console to see the results) http://codepen.io/anon/pen/zvRKYN?editors=001 1135765 1 webkit-bug-importer 2015-10-22 11:51:14 -0700 <rdar://problem/23222219> 1259482 2 mozilla 2016-12-13 12:01:58 -0800 Still seems to be a critical problem. Definitely causes issues when nesting, or when products create deep nesting like react-native-web for example. 1273894 3 l1657572 2017-02-07 00:20:11 -0800 I can confirm. I'm currently using a Flexbox framework which renders great on Chrome and Firefox, but slows to a crawl on Safari. Major issue. 1281807 4 jonlee 2017-02-28 10:51:23 -0800 This is fixed with the latest flex box checkin in b168657. *** This bug has been marked as a duplicate of bug 168657 ***