diff --git a/devtools/server/actors/page-style.js b/devtools/server/actors/page-style.js
index 8f4b17ec5a9d..a288bac23e0a 100644
--- a/devtools/server/actors/page-style.js
+++ b/devtools/server/actors/page-style.js
@@ -805,8 +805,6 @@ class PageStyleActor extends Actor {
         return node.nodeName == "VIDEO";
       case "::file-selector-button":
         return node.nodeName == "INPUT" && node.type == "file";
-      case "::details-content":
-        return node.nodeName == "DETAILS";
       case "::placeholder":
       case "::-moz-placeholder":
         return this._nodeIsTextfieldLike(node);
diff --git a/dom/html/HTMLDetailsElement.cpp b/dom/html/HTMLDetailsElement.cpp
index fe1c8382f7cf..dc020d7704a2 100644
--- a/dom/html/HTMLDetailsElement.cpp
+++ b/dom/html/HTMLDetailsElement.cpp
@@ -149,9 +149,6 @@ void HTMLDetailsElement::SetupShadowTree() {
     if (NS_WARN_IF(!slot)) {
       return;
     }
-    if (StaticPrefs::layout_css_details_content_enabled()) {
-      slot->SetPseudoElementType(PseudoStyleType::detailsContent);
-    }
     sr->AppendChildTo(slot, kNotify, IgnoreErrors());
   }
 }
diff --git a/layout/inspector/tests/test_getCSSPseudoElementNames.html b/layout/inspector/tests/test_getCSSPseudoElementNames.html
index fb96ddb2be28..87c80f46a3a6 100644
--- a/layout/inspector/tests/test_getCSSPseudoElementNames.html
+++ b/layout/inspector/tests/test_getCSSPseudoElementNames.html
@@ -36,7 +36,6 @@
       "::-moz-range-progress",
       "::-moz-range-thumb",
       "::-moz-range-track",
-      "::details-content",
     ]);
 
     let names = InspectorUtils.getCSSPseudoElementNames();
diff --git a/layout/style/nsCSSPseudoElementList.h b/layout/style/nsCSSPseudoElementList.h
index 57427275eb3e..2bb9d3bcf52f 100644
--- a/layout/style/nsCSSPseudoElementList.h
+++ b/layout/style/nsCSSPseudoElementList.h
@@ -120,8 +120,3 @@ CSS_PSEUDO_ELEMENT(sliderThumb, ":slider-thumb",
 CSS_PSEUDO_ELEMENT(sliderFill, ":slider-fill",
                    CSS_PSEUDO_ELEMENT_SUPPORTS_USER_ACTION_STATE |
                    CSS_PSEUDO_ELEMENT_ENABLED_IN_UA_SHEETS_AND_CHROME)
-
-// The content in a <details> element that is shown when the element is open.
-CSS_PSEUDO_ELEMENT(detailsContent, ":details-content",
-                   CSS_PSEUDO_ELEMENT_SUPPORTS_USER_ACTION_STATE |
-                   CSS_PSEUDO_ELEMENT_ENABLED_IN_UA_SHEETS_AND_CHROME)
diff --git a/layout/style/nsCSSPseudoElements.h b/layout/style/nsCSSPseudoElements.h
index ab12a25d51bf..743ca0de73be 100644
--- a/layout/style/nsCSSPseudoElements.h
+++ b/layout/style/nsCSSPseudoElements.h
@@ -124,8 +124,6 @@ class nsCSSPseudoElements {
       case Type::sliderThumb:
       case Type::sliderFill:
         return mozilla::StaticPrefs::layout_css_modern_range_pseudos_enabled();
-      case Type::detailsContent:
-        return mozilla::StaticPrefs::layout_css_details_content_enabled();
       case Type::viewTransition:
       case Type::viewTransitionGroup:
       case Type::viewTransitionImagePair:
diff --git a/layout/style/res/details.css b/layout/style/res/details.css
index fd94d1c0bfad..2bf1d0886780 100644
--- a/layout/style/res/details.css
+++ b/layout/style/res/details.css
@@ -2,7 +2,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-/* The slot:not([name]) don't match once ::details-content is enabled, and should be removed */
 slot:not([name]) {
   display: block;
   content-visibility: hidden;
diff --git a/layout/style/res/html.css b/layout/style/res/html.css
index 75c2bcb7c186..9ca4548aa1b4 100644
--- a/layout/style/res/html.css
+++ b/layout/style/res/html.css
@@ -703,6 +703,9 @@ iframe:fullscreen {
  *
  * Note that these rules need to be duplicated in details.css for the anonymous
  * summary, which wouldn't match otherwise.
+ *
+ * The spec here says something different, see
+ * https://github.com/whatwg/html/issues/8610
  */
 details > summary:first-of-type {
   display: list-item;
@@ -713,14 +716,6 @@ details[open] > summary:first-of-type {
   list-style-type: disclosure-open;
 }
 
-details::details-content {
-  display: block;
-  content-visibility: hidden;
-}
-details[open]::details-content {
-  content-visibility: revert;
-}
-
 /* media elements */
 video {
   object-fit: contain;
diff --git a/modules/libpref/init/StaticPrefList.yaml b/modules/libpref/init/StaticPrefList.yaml
index 995393796cf4..2d39a7928186 100644
--- a/modules/libpref/init/StaticPrefList.yaml
+++ b/modules/libpref/init/StaticPrefList.yaml
@@ -10444,13 +10444,6 @@
   value: false
   mirror: always
 
-# Is support for the ::details-content pseudo-element enabled?
-- name: layout.css.details-content.enabled
-  type: RelaxedAtomicBool
-  value: false
-  mirror: always
-  rust: true
-
 # Is 'content:none' supported on (non-pseudo) elements?
 - name: layout.css.element-content-none.enabled
   type: RelaxedAtomicBool
diff --git a/servo/components/style/gecko/pseudo_element.rs b/servo/components/style/gecko/pseudo_element.rs
index fc7ac7cef7ea..dec93ae51290 100644
--- a/servo/components/style/gecko/pseudo_element.rs
+++ b/servo/components/style/gecko/pseudo_element.rs
@@ -39,8 +39,7 @@ impl ::selectors::parser::PseudoElement for PseudoElement {
                 Self::After |
                 Self::Marker |
                 Self::Placeholder |
-                Self::FileSelectorButton |
-                Self::DetailsContent
+                Self::FileSelectorButton
         )
     }
 
@@ -194,7 +193,7 @@ impl PseudoElement {
     /// Whether this pseudo-element is "part-like", which means that it inherits from its regular
     /// flat tree parent, which might not be the originating element.
     pub fn is_part_like(&self) -> bool {
-        self.is_named_view_transition() || *self == PseudoElement::DetailsContent
+        self.is_named_view_transition()
     }
 
     /// The count we contribute to the specificity from this pseudo-element.
@@ -227,9 +226,6 @@ impl PseudoElement {
             Self::SliderFill | Self::SliderTrack | Self::SliderThumb => {
                 pref!("layout.css.modern-range-pseudos.enabled")
             },
-            Self::DetailsContent => {
-                pref!("layout.css.details-content.enabled")
-            },
             Self::ViewTransition |
             Self::ViewTransitionGroup(..) |
             Self::ViewTransitionImagePair(..) |
diff --git a/servo/components/style/style_adjuster.rs b/servo/components/style/style_adjuster.rs
index 99bb4949119c..d73753dde850 100644
--- a/servo/components/style/style_adjuster.rs
+++ b/servo/components/style/style_adjuster.rs
@@ -554,7 +554,6 @@ impl<'a, 'b: 'a> StyleAdjuster<'a, 'b> {
 
         // FIXME(emilio): ::before and ::after should support display: contents,
         // see bug 1418138.
-        // FIXME(bug 1954140): Element-backed pseudo elements should support display: contents.
         if self.style.pseudo.is_some() {
             self.style.mutate_box().set_display(Display::Inline);
             return;
diff --git a/servo/components/style/style_resolver.rs b/servo/components/style/style_resolver.rs
index 8b55e154de66..33265d588495 100644
--- a/servo/components/style/style_resolver.rs
+++ b/servo/components/style/style_resolver.rs
@@ -296,7 +296,6 @@ where
 
         let mut pseudo_styles = EagerPseudoStyles::default();
 
-        // FIXME(bug 1954142): This should account for element-backed pseudo elements.
         if !self.element.is_pseudo_element() {
             let layout_parent_style_for_pseudo =
                 layout_parent_style_for_pseudo(&primary_style, layout_parent_style);
diff --git a/testing/web-platform/meta/html/rendering/the-details-element/__dir__.ini b/testing/web-platform/meta/html/rendering/the-details-element/__dir__.ini
index 65d629caed9c..57fd9cef6d91 100644
--- a/testing/web-platform/meta/html/rendering/the-details-element/__dir__.ini
+++ b/testing/web-platform/meta/html/rendering/the-details-element/__dir__.ini
@@ -1,2 +1,2 @@
-prefs: [layout.details.force-block-layout:false,layout.css.details-content.enabled:true]
+prefs: [layout.details.force-block-layout:false]
 leak-threshold: [default:51200]
diff --git a/testing/web-platform/meta/html/rendering/the-details-element/details-pseudo-elements-001.html.ini b/testing/web-platform/meta/html/rendering/the-details-element/details-pseudo-elements-001.html.ini
new file mode 100644
index 000000000000..9096d743875b
--- /dev/null
+++ b/testing/web-platform/meta/html/rendering/the-details-element/details-pseudo-elements-001.html.ini
@@ -0,0 +1,2 @@
+[details-pseudo-elements-001.html]
+  expected: FAIL
diff --git a/testing/web-platform/meta/html/rendering/the-details-element/details-pseudo-elements-002.html.ini b/testing/web-platform/meta/html/rendering/the-details-element/details-pseudo-elements-002.html.ini
new file mode 100644
index 000000000000..29476194e408
--- /dev/null
+++ b/testing/web-platform/meta/html/rendering/the-details-element/details-pseudo-elements-002.html.ini
@@ -0,0 +1,2 @@
+[details-pseudo-elements-002.html]
+  expected: FAIL
diff --git a/testing/web-platform/meta/html/rendering/the-details-element/details-pseudo-elements-003.html.ini b/testing/web-platform/meta/html/rendering/the-details-element/details-pseudo-elements-003.html.ini
new file mode 100644
index 000000000000..7ba56cc1ea22
--- /dev/null
+++ b/testing/web-platform/meta/html/rendering/the-details-element/details-pseudo-elements-003.html.ini
@@ -0,0 +1,2 @@
+[details-pseudo-elements-003.html]
+  expected: FAIL
diff --git a/testing/web-platform/meta/html/rendering/the-details-element/details-pseudo-elements-006.html.ini b/testing/web-platform/meta/html/rendering/the-details-element/details-pseudo-elements-006.html.ini
new file mode 100644
index 000000000000..79e18b7d6cd4
--- /dev/null
+++ b/testing/web-platform/meta/html/rendering/the-details-element/details-pseudo-elements-006.html.ini
@@ -0,0 +1,3 @@
+[details-pseudo-elements-006.html]
+  [::details-content matches :hover when mouse pointer is over it]
+    expected: FAIL
diff --git a/xpcom/ds/StaticAtoms.py b/xpcom/ds/StaticAtoms.py
index e060f6cd2009..00c40546e2ae 100644
--- a/xpcom/ds/StaticAtoms.py
+++ b/xpcom/ds/StaticAtoms.py
@@ -2542,7 +2542,6 @@ STATIC_ATOMS = [
     PseudoElementAtom("PseudoElement_sliderTrack", ":slider-track"),
     PseudoElementAtom("PseudoElement_sliderThumb", ":slider-thumb"),
     PseudoElementAtom("PseudoElement_sliderFill", ":slider-fill"),
-    PseudoElementAtom("PseudoElement_detailsContent", ":details-content"),
     # CSS anonymous boxes -- these must appear in the same order as
     # in nsCSSAnonBoxList.h
     NonInheritingAnonBoxAtom("AnonBox_oofPlaceholder", ":-moz-oof-placeholder"),