Per the spec https://drafts.csswg.org/css-scoping/#slotted-pseudo, the ::slotted() selector should only be applied to elements after flattening. Example: https://jsbin.com/ruwesaj/edit?html,output The following style: ::slotted(.hide) { display: none; } should not apply to the intermediate: <slot class="hide"></slot>
Is this related to bug 169948?
(In reply to Simon Fraser (smfr) from comment #1) > Is this related to bug 169948? Yup. That bug is now not to be fixed given the latest discussion at CSS WG: https://github.com/w3c/csswg-drafts/issues/5482
This is working now.