diff --git a/Libraries/LibWeb/Layout/FormattingContext.cpp b/Libraries/LibWeb/Layout/FormattingContext.cpp
index 726be189a8..3cd6a94d68 100644
--- a/Libraries/LibWeb/Layout/FormattingContext.cpp
+++ b/Libraries/LibWeb/Layout/FormattingContext.cpp
@@ -226,6 +226,19 @@ OwnPtr<FormattingContext> FormattingContext::create_independent_formatting_conte
     }
 }
 
+NonnullOwnPtr<FormattingContext> FormattingContext::create_independent_formatting_context(LayoutState& state, LayoutMode layout_mode, Box const& child_box)
+{
+    if (auto context = create_independent_formatting_context_if_needed(state, layout_mode, child_box))
+        return context.release_nonnull();
+
+    if (auto child_block_container = as_if<BlockContainer>(child_box))
+        return make<BlockFormattingContext>(state, layout_mode, *child_block_container, nullptr);
+
+    // HACK: Instead of crashing in scenarios that assume the formatting context can be created, create a dummy formatting context that does nothing.
+    dbgln("FIXME: An independent formatting context was requested from a Box that does not have a formatting context type. A dummy formatting context will be created instead.");
+    return make<DummyFormattingContext>(state, layout_mode, child_box);
+}
+
 OwnPtr<FormattingContext> FormattingContext::layout_inside(Box const& child_box, LayoutMode layout_mode, AvailableSpace const& available_space)
 {
     {
@@ -1167,7 +1180,8 @@ CSSPixelRect FormattingContext::content_box_rect_in_static_position_ancestor_coo
 {
     auto box_used_values = m_state.get(box);
     CSSPixelRect rect = { { 0, 0 }, box_used_values.content_size() };
-    VERIFY(box_used_values.offset.is_zero()); // Set as result of this calculation
+    // FIXME: ListItemMarkerBox's should also run this assertion once it has a supported FormattingContext type
+    VERIFY(box_used_values.offset.is_zero() || box.is_list_item_marker_box()); // Set as result of this calculation
     for (auto const* current = box.static_position_containing_block(); current; current = current->containing_block()) {
         if (current == box.containing_block())
             return rect;
@@ -1454,10 +1468,7 @@ CSSPixels FormattingContext::calculate_min_content_width(Layout::Box const& box)
     box_state.width_constraint = SizeConstraint::MinContent;
     box_state.set_indefinite_content_width();
 
-    auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, LayoutMode::IntrinsicSizing, box);
-    if (!context) {
-        context = make<BlockFormattingContext>(throwaway_state, LayoutMode::IntrinsicSizing, as<BlockContainer>(box), nullptr);
-    }
+    auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context(throwaway_state, LayoutMode::IntrinsicSizing, box);
 
     auto available_width = AvailableSize::make_min_content();
     auto available_height = box_state.has_definite_height()
@@ -1494,10 +1505,7 @@ CSSPixels FormattingContext::calculate_max_content_width(Layout::Box const& box)
     box_state.border_right = actual_box_state.border_right;
     box_state.padding_right = actual_box_state.padding_right;
 
-    auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, LayoutMode::IntrinsicSizing, box);
-    if (!context) {
-        context = make<BlockFormattingContext>(throwaway_state, LayoutMode::IntrinsicSizing, as<BlockContainer>(box), nullptr);
-    }
+    auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context(throwaway_state, LayoutMode::IntrinsicSizing, box);
 
     auto available_width = AvailableSize::make_max_content();
     auto available_height = box_state.has_definite_height()
@@ -1535,10 +1543,7 @@ CSSPixels FormattingContext::calculate_min_content_height(Layout::Box const& box
     box_state.set_indefinite_content_height();
     box_state.set_content_width(width);
 
-    auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, LayoutMode::IntrinsicSizing, box);
-    if (!context) {
-        context = make<BlockFormattingContext>(throwaway_state, LayoutMode::IntrinsicSizing, as<BlockContainer>(box), nullptr);
-    }
+    auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context(throwaway_state, LayoutMode::IntrinsicSizing, box);
 
     context->run(AvailableSpace(AvailableSize::make_definite(width), AvailableSize::make_min_content()));
 
@@ -1566,10 +1571,7 @@ CSSPixels FormattingContext::calculate_max_content_height(Layout::Box const& box
     box_state.set_indefinite_content_height();
     box_state.set_content_width(width);
 
-    auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context_if_needed(throwaway_state, LayoutMode::IntrinsicSizing, box);
-    if (!context) {
-        context = make<BlockFormattingContext>(throwaway_state, LayoutMode::IntrinsicSizing, as<BlockContainer>(box), nullptr);
-    }
+    auto context = const_cast<FormattingContext*>(this)->create_independent_formatting_context(throwaway_state, LayoutMode::IntrinsicSizing, box);
 
     context->run(AvailableSpace(AvailableSize::make_definite(width), AvailableSize::make_max_content()));
 
diff --git a/Libraries/LibWeb/Layout/FormattingContext.h b/Libraries/LibWeb/Layout/FormattingContext.h
index c5b0b91cf2..2645b0ebca 100644
--- a/Libraries/LibWeb/Layout/FormattingContext.h
+++ b/Libraries/LibWeb/Layout/FormattingContext.h
@@ -64,6 +64,7 @@ public:
     CSSPixels compute_height_for_replaced_element(Box const&, AvailableSpace const&) const;
 
     OwnPtr<FormattingContext> create_independent_formatting_context_if_needed(LayoutState&, LayoutMode, Box const& child_box);
+    NonnullOwnPtr<FormattingContext> create_independent_formatting_context(LayoutState&, LayoutMode, Box const& child_box);
 
     virtual void parent_context_did_dimension_child_root_box() { }
 
diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/css-pseudo/parsing/marker-supported-properties-in-animation.txt b/Tests/LibWeb/Text/expected/wpt-import/css/css-pseudo/parsing/marker-supported-properties-in-animation.txt
new file mode 100644
index 0000000000..eb77fa9df4
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/css-pseudo/parsing/marker-supported-properties-in-animation.txt
@@ -0,0 +1,102 @@
+Harness status: OK
+
+Found 96 tests
+
+39 Pass
+57 Fail
+Pass	Animation of font in ::marker
+Pass	Animation of font-family in ::marker
+Fail	Animation of font-feature-settings in ::marker
+Fail	Animation of font-kerning in ::marker
+Pass	Animation of font-size in ::marker
+Fail	Animation of font-size-adjust in ::marker
+Pass	Animation of font-stretch in ::marker
+Pass	Animation of font-style in ::marker
+Fail	Animation of font-synthesis in ::marker
+Fail	Animation of font-synthesis-small-caps in ::marker
+Fail	Animation of font-synthesis-style in ::marker
+Fail	Animation of font-synthesis-weight in ::marker
+Pass	Animation of font-variant in ::marker
+Pass	Animation of font-variant-caps in ::marker
+Fail	Animation of font-variant-east-asian in ::marker
+Fail	Animation of font-variant-ligatures in ::marker
+Fail	Animation of font-variant-numeric in ::marker
+Fail	Animation of font-variant-position in ::marker
+Pass	Animation of font-weight in ::marker
+Pass	Animation of line-height in ::marker
+Fail	Animation of white-space in ::marker
+Fail	Animation of color in ::marker
+Fail	Animation of text-combine-upright in ::marker
+Pass	Animation of unicode-bidi in ::marker
+Pass	Animation of direction in ::marker
+Fail	Animation of content in ::marker
+Fail	Animation of hyphens in ::marker
+Fail	Animation of letter-spacing in ::marker
+Fail	Animation of line-break in ::marker
+Fail	Animation of overflow-wrap in ::marker
+Fail	Animation of tab-size in ::marker
+Fail	Animation of text-transform in ::marker
+Fail	Animation of word-break in ::marker
+Fail	Animation of word-spacing in ::marker
+Fail	Animation of text-decoration-skip-ink in ::marker
+Fail	Animation of text-emphasis in ::marker
+Fail	Animation of text-emphasis-color in ::marker
+Fail	Animation of text-emphasis-position in ::marker
+Fail	Animation of text-emphasis-style in ::marker
+Fail	Animation of text-shadow in ::marker
+Fail	Animation of cursor in ::marker
+Pass	Animation of display in ::marker
+Pass	Animation of position in ::marker
+Pass	Animation of float in ::marker
+Fail	Animation of list-style in ::marker
+Pass	Animation of list-style-image in ::marker
+Pass	Animation of list-style-position in ::marker
+Pass	Animation of list-style-type in ::marker
+Pass	Transition of font in ::marker
+Pass	Transition of font-family in ::marker
+Pass	Transition of font-feature-settings in ::marker
+Pass	Transition of font-kerning in ::marker
+Fail	Transition of font-size in ::marker
+Fail	Transition of font-size-adjust in ::marker
+Fail	Transition of font-stretch in ::marker
+Fail	Transition of font-style in ::marker
+Fail	Transition of font-synthesis in ::marker
+Fail	Transition of font-synthesis-small-caps in ::marker
+Fail	Transition of font-synthesis-style in ::marker
+Fail	Transition of font-synthesis-weight in ::marker
+Pass	Transition of font-variant in ::marker
+Pass	Transition of font-variant-caps in ::marker
+Pass	Transition of font-variant-east-asian in ::marker
+Pass	Transition of font-variant-ligatures in ::marker
+Pass	Transition of font-variant-numeric in ::marker
+Pass	Transition of font-variant-position in ::marker
+Fail	Transition of font-weight in ::marker
+Fail	Transition of line-height in ::marker
+Pass	Transition of white-space in ::marker
+Pass	Transition of color in ::marker
+Fail	Transition of text-combine-upright in ::marker
+Pass	Transition of unicode-bidi in ::marker
+Pass	Transition of direction in ::marker
+Pass	Transition of content in ::marker
+Fail	Transition of hyphens in ::marker
+Pass	Transition of letter-spacing in ::marker
+Fail	Transition of line-break in ::marker
+Pass	Transition of overflow-wrap in ::marker
+Pass	Transition of tab-size in ::marker
+Pass	Transition of text-transform in ::marker
+Pass	Transition of word-break in ::marker
+Pass	Transition of word-spacing in ::marker
+Fail	Transition of text-decoration-skip-ink in ::marker
+Fail	Transition of text-emphasis in ::marker
+Fail	Transition of text-emphasis-color in ::marker
+Fail	Transition of text-emphasis-position in ::marker
+Fail	Transition of text-emphasis-style in ::marker
+Fail	Transition of text-shadow in ::marker
+Pass	Transition of cursor in ::marker
+Fail	Transition of display in ::marker
+Fail	Transition of position in ::marker
+Fail	Transition of float in ::marker
+Fail	Transition of list-style in ::marker
+Fail	Transition of list-style-image in ::marker
+Fail	Transition of list-style-position in ::marker
+Fail	Transition of list-style-type in ::marker
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/input/wpt-import/css/css-pseudo/parsing/marker-supported-properties-in-animation.html b/Tests/LibWeb/Text/input/wpt-import/css/css-pseudo/parsing/marker-supported-properties-in-animation.html
new file mode 100644
index 0000000000..9dad046d6d
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/css/css-pseudo/parsing/marker-supported-properties-in-animation.html
@@ -0,0 +1,405 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Pseudo-Elements Test: Supported properties in ::marker animations</title>
+<link rel="help" href="https://drafts.csswg.org/css-pseudo-4/#marker-pseudo">
+<link rel="help" href="https://drafts.csswg.org/css-animations-1/#keyframes">
+<link rel="help" href="https://drafts.csswg.org/css-transitions-1/#transitions">
+<link rel="author" title="Oriol Brufau" href="mailto:obrufau@igalia.com">
+<meta name="assert" content="This test checks ::marker supports animations and transitions, but only for the properties that apply to ::marker." />
+<style id="style"></style>
+<script src="../../../resources/testharness.js"></script>
+<script src="../../../resources/testharnessreport.js"></script>
+<div id="log"></div>
+<ul>
+  <li id="target">target</li>
+</ul>
+<script>
+const interpolationTests = [
+  // ::marker supports all font properties.
+  {
+    property: "font",
+    from: "oblique normal 100 ultra-condensed 5px / 20px serif",
+    to: "italic small-caps 900 ultra-expanded 25px / 50px Ahem",
+    midPoint: ["italic small-caps 500 expanded 15px / 35px Ahem", "italic small-caps 500 expanded 15px/35px Ahem"],
+  },
+  {
+    property: "font-family",
+    from: "serif",
+    to: "Ahem",
+    midPoint: "Ahem",
+  },
+  {
+    property: "font-feature-settings",
+    from: "'c2sc'",
+    to: "'smcp'",
+    midPoint: "\"smcp\"",
+  },
+  {
+    property: "font-kerning",
+    from: "normal",
+    to: "none",
+    midPoint: "none",
+  },
+  {
+    property: "font-size",
+    from: "5px",
+    to: "25px",
+    midPoint: "15px",
+  },
+  {
+    property: "font-size-adjust",
+    from: "1",
+    to: "3",
+    midPoint: "2",
+  },
+  {
+    property: "font-stretch",
+    from: "ultra-condensed",
+    to: "ultra-expanded",
+    midPoint: ["expanded", "125%"],
+  },
+  {
+    property: "font-style",
+    from: "oblique",
+    to: "italic",
+    midPoint: "italic",
+  },
+  {
+    property: "font-synthesis",
+    from: "weight",
+    to: "none",
+    midPoint: "none",
+  },
+  {
+    property: "font-synthesis-small-caps",
+    from: "auto",
+    to: "none",
+    midPoint: "none",
+  },
+  {
+    property: "font-synthesis-style",
+    from: "auto",
+    to: "none",
+    midPoint: "none",
+  },
+  {
+    property: "font-synthesis-weight",
+    from: "auto",
+    to: "none",
+    midPoint: "none",
+  },
+  {
+    property: "font-variant",
+    from: "unicase",
+    to: "small-caps",
+    midPoint: "small-caps",
+  },
+  {
+    property: "font-variant-caps",
+    from: "unicase",
+    to: "small-caps",
+    midPoint: "small-caps",
+  },
+  {
+    property: "font-variant-east-asian",
+    from: "proportional-width",
+    to: "full-width",
+    midPoint: "full-width",
+  },
+  {
+    property: "font-variant-ligatures",
+    from: "no-historical-ligatures",
+    to: "historical-ligatures",
+    midPoint: "historical-ligatures",
+  },
+  {
+    property: "font-variant-numeric",
+    from: "ordinal",
+    to: "slashed-zero",
+    midPoint: "slashed-zero",
+  },
+  {
+    property: "font-variant-position",
+    from: "super",
+    to: "sub",
+    midPoint: "sub",
+  },
+  {
+    property: "font-weight",
+    from: "100",
+    to: "900",
+    midPoint: "500",
+  },
+
+  // `line-height` is not a font property but is a longhand of `font`, and is also supported.
+  {
+    property: "line-height",
+    from: "20px",
+    to: "50px",
+    midPoint: "35px",
+  },
+
+  // ::marker supports `white-space`
+  {
+    property: "white-space",
+    from: "pre-line",
+    to: "nowrap",
+    midPoint: "nowrap",
+  },
+
+  // ::marker supports `color`
+  {
+    property: "color",
+    from: "rgb(0, 100, 200)",
+    to: "rgb(100, 200, 0)",
+    midPoint: "rgb(50, 150, 100)",
+  },
+
+  // ::marker supports `text-combine-upright`, `unicode-bidi` and `direction`,
+  // but they are not animatable.
+  {
+    property: "text-combine-upright",
+    from: "all",
+    to: "all",
+    midPoint: null,
+  },
+  {
+    property: "unicode-bidi",
+    from: "embed",
+    to: "plaintext",
+    midPoint: null,
+  },
+  {
+    property: "direction",
+    from: "rtl",
+    to: "rtl",
+    midPoint: null,
+  },
+
+  // ::marker supports `content`
+  {
+    property: "content",
+    from: "'foo'",
+    to: "'bar'",
+    midPoint: "\"bar\"",
+  },
+
+  // ::marker supports text properties.
+  {
+    property: "hyphens",
+    from: "manual",
+    to: "none",
+    midPoint: "none",
+  },
+  {
+    property: "letter-spacing",
+    from: "0px",
+    to: "20px",
+    midPoint: "10px",
+  },
+  {
+    property: "line-break",
+    from: "strict",
+    to: "anywhere",
+    midPoint: "anywhere",
+  },
+  {
+    property: "overflow-wrap",
+    from: "break-word",
+    to: "anywhere",
+    midPoint: "anywhere",
+  },
+  {
+    property: "tab-size",
+    from: "0px",
+    to: "20px",
+    midPoint: "10px",
+  },
+  {
+    property: "text-transform",
+    from: "lowercase",
+    to: "uppercase",
+    midPoint: "uppercase",
+  },
+  {
+    property: "word-break",
+    from: "break-all",
+    to: "break-word",
+    midPoint: "break-word",
+  },
+  {
+    property: "word-spacing",
+    from: "0px",
+    to: "20px",
+    midPoint: "10px",
+  },
+
+  // ::marker supports inherited text decoration properties.
+  {
+    property: "text-decoration-skip-ink",
+    from: "auto",
+    to: "none",
+    midPoint: "none",
+  },
+  {
+    property: "text-emphasis",
+    from: "dot rgb(0, 200, 0)",
+    to: "triangle rgb(100, 0, 200)",
+    midPoint: "triangle rgb(50, 100, 100)",
+  },
+  {
+    property: "text-emphasis-color",
+    from: "rgb(0, 200, 0)",
+    to: "rgb(100, 0, 200)",
+    midPoint: "rgb(50, 100, 100)",
+  },
+  {
+    property: "text-emphasis-position",
+    from: "over right",
+    to: "under left",
+    midPoint: "under left",
+  },
+  {
+    property: "text-emphasis-style",
+    from: "filled dot",
+    to: "filled triangle",
+    midPoint: "triangle",
+  },
+  {
+    property: "text-shadow",
+    from: "rgb(0, 200, 0) 1px 2px 3px",
+    to: "rgb(100, 0, 200) 3px 2px 1px",
+    midPoint: "rgb(50, 100, 100) 2px 2px 2px",
+  },
+
+  // ::marker supports `cursor`.
+  {
+    property: "cursor",
+    from: "auto",
+    to: "move",
+    midPoint: "move",
+  },
+
+  // ::marker does NOT support layout properties
+  {
+    property: "display",
+    from: "flex",
+    to: "none",
+    midPoint: ["block", "inline", "inline-block"],
+  },
+  {
+    property: "position",
+    from: "fixed",
+    to: "absolute",
+    midPoint: "static",
+  },
+  {
+    property: "float",
+    from: "left",
+    to: "right",
+    midPoint: "none",
+  },
+
+  // ::marker does NOT support list properties despite being affected by them,
+  // they apply to the list item instead.
+  {
+    property: "list-style",
+    from: "inside url('foo') square",
+    to: "inside url('bar') decimal",
+    midPoint: "outside none disc",
+  },
+  {
+    property: "list-style-image",
+    from: "url('foo')",
+    to: "url('bar')",
+    midPoint: "none",
+  },
+  {
+    property: "list-style-position",
+    from: "inside",
+    to: "inside",
+    midPoint: "outside",
+  },
+  {
+    property: "list-style-type",
+    from: "square",
+    to: "decimal",
+    midPoint: "disc",
+  },
+];
+
+const target = document.getElementById("target");
+const styleElement = document.getElementById("style");
+const markerStyle = getComputedStyle(target, "::marker");
+
+function check({property, from, to, midPoint}) {
+  assert_true(property in markerStyle, property + " doesn't seem to be supported in the computed style");
+  assert_true(CSS.supports(property, from), `'${from}' is a supported value for ${property}.`);
+  assert_true(CSS.supports(property, to), `'${to}' is a supported value for ${property}.`);
+  const computed = markerStyle.getPropertyValue(property);
+  if (Array.isArray(midPoint)) {
+    assert_in_array(computed, midPoint);
+  } else {
+    assert_equals(computed, midPoint);
+  }
+}
+
+function testAnimations(interpolationTests) {
+  styleElement.textContent = `
+    ::marker {
+      animation: anim 2s -1s paused linear;
+    }
+    @keyframes anim {
+      from {}
+      to {}
+    }
+  `;
+  const keyframes = styleElement.sheet.cssRules[1];
+  const fromStyle = keyframes.cssRules[0].style;
+  const toStyle = keyframes.cssRules[1].style;
+  for (let {property, from, to, midPoint} of interpolationTests) {
+    fromStyle.cssText = "";
+    toStyle.cssText = "";
+    if (midPoint == null) {
+      midPoint = markerStyle.getPropertyValue(property);
+    }
+    fromStyle.setProperty(property, from);
+    toStyle.setProperty(property, to);
+    test(() => {
+      check({property, from, to, midPoint});
+    }, `Animation of ${property} in ::marker`);
+  }
+}
+
+function testTransitions(interpolationTests) {
+  styleElement.textContent = `
+    .transition::marker {
+      transition: all 2s -1s linear;
+    }
+    .from::marker {}
+    .to::marker {}
+  `;
+  const fromStyle = styleElement.sheet.cssRules[1].style;
+  const toStyle = styleElement.sheet.cssRules[2].style;
+  for (let {property, from, to, midPoint} of interpolationTests) {
+    fromStyle.cssText = "";
+    toStyle.cssText = "";
+    if (midPoint == null) {
+      midPoint = to;
+    }
+    fromStyle.setProperty(property, from);
+    toStyle.setProperty(property, to);
+    target.className = "from";
+    markerStyle.width;
+    target.classList.add("transition");
+    markerStyle.width;
+    target.classList.add("to");
+    test(() => {
+      check({property, from, to, midPoint});
+    }, `Transition of ${property} in ::marker`);
+  }
+}
+
+testAnimations(interpolationTests);
+testTransitions(interpolationTests);
+</script>