The author experienced a significant slowdown in a web app’s dashboard, suspecting React was to blame. Initial checks revealed React-related issues, but addressing them didn’t resolve the problem. The slowdown was specific to Safari, prompting deeper investigation into potential causes like server performance and third-party JavaScript, which were ruled out. Ultimately, the performance inspector showed that Safari was struggling with layout processes, primarily due to the use of a heart emoji in the feedback button. Removal of this emoji drastically improved layout time from 1600ms to just 2ms. The culprit was identified as the Noto Color Emoji font, which relies on the COLRv1 specification that Safari handled poorly, resulting in excessive layout times. The author noted that while Noto Color Emoji provides cross-platform consistency, it’s problematic on Apple devices. A minimal test case was created to report the bug, and the author advised against using Noto Color Emoji on Apple platforms until the issue is resolved.