diff --git a/Libraries/LibWeb/CSS/Enums.json b/Libraries/LibWeb/CSS/Enums.json
index f8ef938245a..caa19939a24 100644
--- a/Libraries/LibWeb/CSS/Enums.json
+++ b/Libraries/LibWeb/CSS/Enums.json
@@ -491,6 +491,11 @@
     "luminance",
     "alpha"
   ],
+  "masking-mode": [
+    "alpha",
+    "luminance",
+    "match-source"
+  ],
   "math-shift": [
     "normal",
     "compact"
diff --git a/Libraries/LibWeb/CSS/Keywords.json b/Libraries/LibWeb/CSS/Keywords.json
index df343c11f8d..4b3f79b37b1 100644
--- a/Libraries/LibWeb/CSS/Keywords.json
+++ b/Libraries/LibWeb/CSS/Keywords.json
@@ -319,6 +319,7 @@
   "mark",
   "marktext",
   "match-parent",
+  "match-source",
   "math",
   "math-auto",
   "max-content",
diff --git a/Libraries/LibWeb/CSS/Parser/PropertyParsing.cpp b/Libraries/LibWeb/CSS/Parser/PropertyParsing.cpp
index 4b594e4e617..e5c8cdc9504 100644
--- a/Libraries/LibWeb/CSS/Parser/PropertyParsing.cpp
+++ b/Libraries/LibWeb/CSS/Parser/PropertyParsing.cpp
@@ -665,6 +665,7 @@ Parser::ParseErrorOr<NonnullRefPtr<CSSStyleValue const>> Parser::parse_css_value
             return parsed_value.release_nonnull();
         return ParseError::SyntaxError;
     case PropertyID::MaskComposite:
+    case PropertyID::MaskMode:
         if (auto parsed_value = parse_simple_comma_separated_value_list(property_id, tokens))
             return parsed_value.release_nonnull();
         return ParseError::SyntaxError;
diff --git a/Libraries/LibWeb/CSS/Properties.json b/Libraries/LibWeb/CSS/Properties.json
index a5de1d29649..a169d004cb3 100644
--- a/Libraries/LibWeb/CSS/Properties.json
+++ b/Libraries/LibWeb/CSS/Properties.json
@@ -2406,6 +2406,15 @@
     ],
     "initial": "none"
   },
+  "mask-mode": {
+    "animation-type": "discrete",
+    "inherited": false,
+    "affects-layout": false,
+    "valid-types": [
+      "masking-mode"
+    ],
+    "initial": "match-source"
+  },
   "mask-type": {
     "animation-type": "discrete",
     "inherited": false,
diff --git a/Tests/LibWeb/Text/expected/css/CSSStyleDeclaration-has-indexed-property-getter.txt b/Tests/LibWeb/Text/expected/css/CSSStyleDeclaration-has-indexed-property-getter.txt
index 855eb22263c..165fd21b6e4 100644
--- a/Tests/LibWeb/Text/expected/css/CSSStyleDeclaration-has-indexed-property-getter.txt
+++ b/Tests/LibWeb/Text/expected/css/CSSStyleDeclaration-has-indexed-property-getter.txt
@@ -188,6 +188,7 @@ All properties associated with getComputedStyle(document.body):
     "margin-top",
     "mask-composite",
     "mask-image",
+    "mask-mode",
     "mask-type",
     "max-block-size",
     "max-height",
diff --git a/Tests/LibWeb/Text/expected/css/CSSStyleProperties-all-supported-properties-and-default-values.txt b/Tests/LibWeb/Text/expected/css/CSSStyleProperties-all-supported-properties-and-default-values.txt
index 3cfddcece47..f69a9aa04c3 100644
--- a/Tests/LibWeb/Text/expected/css/CSSStyleProperties-all-supported-properties-and-default-values.txt
+++ b/Tests/LibWeb/Text/expected/css/CSSStyleProperties-all-supported-properties-and-default-values.txt
@@ -529,6 +529,8 @@ All supported properties and their default values exposed from CSSStylePropertie
 'mask-composite': 'add'
 'maskImage': 'none'
 'mask-image': 'none'
+'maskMode': 'match-source'
+'mask-mode': 'match-source'
 'maskType': 'luminance'
 'mask-type': 'luminance'
 'mathDepth': '0'
diff --git a/Tests/LibWeb/Text/expected/css/getComputedStyle-print-all.txt b/Tests/LibWeb/Text/expected/css/getComputedStyle-print-all.txt
index ebea47cd7c0..b94e83e407d 100644
--- a/Tests/LibWeb/Text/expected/css/getComputedStyle-print-all.txt
+++ b/Tests/LibWeb/Text/expected/css/getComputedStyle-print-all.txt
@@ -186,6 +186,7 @@ margin-right: 8px
 margin-top: 8px
 mask-composite: add
 mask-image: none
+mask-mode: match-source
 mask-type: luminance
 max-block-size: none
 max-height: none
diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/css-cascade/all-prop-revert-layer.txt b/Tests/LibWeb/Text/expected/wpt-import/css/css-cascade/all-prop-revert-layer.txt
index 1a61420238e..895900c6c20 100644
--- a/Tests/LibWeb/Text/expected/wpt-import/css/css-cascade/all-prop-revert-layer.txt
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/css-cascade/all-prop-revert-layer.txt
@@ -1,8 +1,8 @@
 Harness status: OK
 
-Found 249 tests
+Found 250 tests
 
-242 Pass
+243 Pass
 7 Fail
 Pass	accent-color
 Pass	border-collapse
@@ -187,6 +187,7 @@ Pass	margin-right
 Pass	margin-top
 Pass	mask-composite
 Pass	mask-image
+Pass	mask-mode
 Pass	mask-type
 Pass	max-block-size
 Pass	max-height