diff --git a/Libraries/LibWeb/CSS/Interpolation.cpp b/Libraries/LibWeb/CSS/Interpolation.cpp
index 282c2795c6f..c87cb4f3853 100644
--- a/Libraries/LibWeb/CSS/Interpolation.cpp
+++ b/Libraries/LibWeb/CSS/Interpolation.cpp
@@ -616,6 +616,11 @@ NonnullRefPtr<CSSStyleValue const> interpolate_value(DOM::Element& element, Calc
         auto from_ratio = from.as_ratio().ratio();
         auto to_ratio = to.as_ratio().ratio();
 
+        // https://drafts.csswg.org/css-values/#combine-ratio
+        // If either <ratio> is degenerate, the values cannot be interpolated.
+        if (from_ratio.is_degenerate() || to_ratio.is_degenerate())
+            return delta >= 0.5f ? to : from;
+
         // The interpolation of a <ratio> is defined by converting each <ratio> to a number by dividing the first value
         // by the second (so a ratio of 3 / 2 would become 1.5), taking the logarithm of that result (so the 1.5 would
         // become approximately 0.176), then interpolating those values. The result during the interpolation is
diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/css-sizing/animation/aspect-ratio-interpolation.txt b/Tests/LibWeb/Text/expected/wpt-import/css/css-sizing/animation/aspect-ratio-interpolation.txt
new file mode 100644
index 00000000000..e597bba2f51
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/css-sizing/animation/aspect-ratio-interpolation.txt
@@ -0,0 +1,252 @@
+Harness status: OK
+
+Found 246 tests
+
+184 Pass
+62 Fail
+Fail	CSS Transitions: property <aspect-ratio> from [0.5] to [2] at (-0.5) should be [0.25 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [0.5] to [2] at (0) should be [0.5 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [0.5] to [2] at (0.5) should be [1 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [0.5] to [2] at (1) should be [2 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [0.5] to [2] at (1.5) should be [4 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [0.5] to [2] at (-0.5) should be [0.25 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [0.5] to [2] at (0) should be [0.5 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [0.5] to [2] at (0.5) should be [1 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [0.5] to [2] at (1) should be [2 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [0.5] to [2] at (1.5) should be [4 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [0.5] to [2] at (-0.5) should be [0.25 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [0.5] to [2] at (0) should be [0.5 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [0.5] to [2] at (0.5) should be [1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [0.5] to [2] at (1) should be [2 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [0.5] to [2] at (1.5) should be [4 / 1]
+Pass	Web Animations: property <aspect-ratio> from [0.5] to [2] at (-0.5) should be [0.25 / 1]
+Pass	Web Animations: property <aspect-ratio> from [0.5] to [2] at (0) should be [0.5 / 1]
+Pass	Web Animations: property <aspect-ratio> from [0.5] to [2] at (0.5) should be [1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [0.5] to [2] at (1) should be [2 / 1]
+Pass	Web Animations: property <aspect-ratio> from [0.5] to [2] at (1.5) should be [4 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [1 / 2] to [2 / 1] at (-0.5) should be [0.25 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [1 / 2] to [2 / 1] at (0) should be [0.5 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [1 / 2] to [2 / 1] at (0.5) should be [1 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 2] to [2 / 1] at (1) should be [2 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [1 / 2] to [2 / 1] at (1.5) should be [4 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 2] to [2 / 1] at (-0.5) should be [0.25 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 2] to [2 / 1] at (0) should be [0.5 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 2] to [2 / 1] at (0.5) should be [1 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 2] to [2 / 1] at (1) should be [2 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 2] to [2 / 1] at (1.5) should be [4 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 2] to [2 / 1] at (-0.5) should be [0.25 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 2] to [2 / 1] at (0) should be [0.5 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 2] to [2 / 1] at (0.5) should be [1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 2] to [2 / 1] at (1) should be [2 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 2] to [2 / 1] at (1.5) should be [4 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 2] to [2 / 1] at (-0.5) should be [0.25 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 2] to [2 / 1] at (0) should be [0.5 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 2] to [2 / 1] at (0.5) should be [1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 2] to [2 / 1] at (1) should be [2 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 2] to [2 / 1] at (1.5) should be [4 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [] to [2 / 1] at (-0.5) should be [0.25 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [] to [2 / 1] at (0) should be [0.5 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [] to [2 / 1] at (0.5) should be [1 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [] to [2 / 1] at (1) should be [2 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [] to [2 / 1] at (1.5) should be [4 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [] to [2 / 1] at (-0.5) should be [0.25 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [] to [2 / 1] at (0) should be [0.5 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [] to [2 / 1] at (0.5) should be [1 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [] to [2 / 1] at (1) should be [2 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [] to [2 / 1] at (1.5) should be [4 / 1]
+Fail	CSS Animations: property <aspect-ratio> from [] to [2 / 1] at (-0.5) should be [0.25 / 1]
+Fail	CSS Animations: property <aspect-ratio> from [] to [2 / 1] at (0) should be [0.5 / 1]
+Fail	CSS Animations: property <aspect-ratio> from [] to [2 / 1] at (0.5) should be [1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [] to [2 / 1] at (1) should be [2 / 1]
+Fail	CSS Animations: property <aspect-ratio> from [] to [2 / 1] at (1.5) should be [4 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (-0.5) should be [auto 0.25 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (0) should be [auto 0.5 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (0.5) should be [auto 1 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (1) should be [auto 2 / 1]
+Fail	CSS Transitions: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (1.5) should be [auto 4 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (-0.5) should be [auto 0.25 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (0) should be [auto 0.5 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (0.5) should be [auto 1 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (1) should be [auto 2 / 1]
+Fail	CSS Transitions with transition: all: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (1.5) should be [auto 4 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (-0.5) should be [auto 0.25 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (0) should be [auto 0.5 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (0.5) should be [auto 1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (1) should be [auto 2 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (1.5) should be [auto 4 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (-0.5) should be [auto 0.25 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (0) should be [auto 0.5 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (0.5) should be [auto 1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (1) should be [auto 2 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto 1 / 2] to [auto 2 / 1] at (1.5) should be [auto 4 / 1]
+Fail	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (-0.3) should be [auto]
+Fail	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (0) should be [auto]
+Fail	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (0.3) should be [auto]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (0.5) should be [2 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (0.6) should be [2 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (1) should be [2 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (1.5) should be [2 / 1]
+Fail	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (-0.3) should be [auto]
+Fail	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (0) should be [auto]
+Fail	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (0.3) should be [auto]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (0.5) should be [2 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (0.6) should be [2 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (1) should be [2 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto] to [2 / 1] at (1.5) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto] to [2 / 1] at (-0.3) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto] to [2 / 1] at (0) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto] to [2 / 1] at (0.3) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto] to [2 / 1] at (0.5) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto] to [2 / 1] at (0.6) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto] to [2 / 1] at (1) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto] to [2 / 1] at (1.5) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto] to [2 / 1] at (-0.3) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto] to [2 / 1] at (0) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto] to [2 / 1] at (0.3) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto] to [2 / 1] at (0.5) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto] to [2 / 1] at (0.6) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto] to [2 / 1] at (1) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto] to [2 / 1] at (1.5) should be [2 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto] to [2 / 1] at (-0.3) should be [auto]
+Pass	CSS Animations: property <aspect-ratio> from [auto] to [2 / 1] at (0) should be [auto]
+Pass	CSS Animations: property <aspect-ratio> from [auto] to [2 / 1] at (0.3) should be [auto]
+Pass	CSS Animations: property <aspect-ratio> from [auto] to [2 / 1] at (0.5) should be [2 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto] to [2 / 1] at (0.6) should be [2 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto] to [2 / 1] at (1) should be [2 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto] to [2 / 1] at (1.5) should be [2 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto] to [2 / 1] at (-0.3) should be [auto]
+Pass	Web Animations: property <aspect-ratio> from [auto] to [2 / 1] at (0) should be [auto]
+Pass	Web Animations: property <aspect-ratio> from [auto] to [2 / 1] at (0.3) should be [auto]
+Pass	Web Animations: property <aspect-ratio> from [auto] to [2 / 1] at (0.5) should be [2 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto] to [2 / 1] at (0.6) should be [2 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto] to [2 / 1] at (1) should be [2 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto] to [2 / 1] at (1.5) should be [2 / 1]
+Fail	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (-0.3) should be [auto 1 / 1]
+Fail	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0) should be [auto 1 / 1]
+Fail	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.3) should be [auto 1 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.5) should be [2 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.6) should be [2 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (1) should be [2 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (1.5) should be [2 / 1]
+Fail	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (-0.3) should be [auto 1 / 1]
+Fail	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0) should be [auto 1 / 1]
+Fail	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.3) should be [auto 1 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.5) should be [2 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.6) should be [2 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (1) should be [2 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (1.5) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (-0.3) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.3) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.5) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.6) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (1) should be [2 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (1.5) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (-0.3) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.3) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.5) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.6) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (1) should be [2 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (1.5) should be [2 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (-0.3) should be [auto 1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0) should be [auto 1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.3) should be [auto 1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.5) should be [2 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.6) should be [2 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (1) should be [2 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (1.5) should be [2 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (-0.3) should be [auto 1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0) should be [auto 1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.3) should be [auto 1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.5) should be [2 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (0.6) should be [2 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (1) should be [2 / 1]
+Pass	Web Animations: property <aspect-ratio> from [auto 1 / 1] to [2 / 1] at (1.5) should be [2 / 1]
+Fail	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (-0.3) should be [1 / 0]
+Fail	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0) should be [1 / 0]
+Fail	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.3) should be [1 / 0]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.5) should be [1 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.6) should be [1 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (1) should be [1 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (1.5) should be [1 / 1]
+Fail	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (-0.3) should be [1 / 0]
+Fail	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0) should be [1 / 0]
+Fail	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.3) should be [1 / 0]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.5) should be [1 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.6) should be [1 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (1) should be [1 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 0] to [1 / 1] at (1.5) should be [1 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 0] to [1 / 1] at (-0.3) should be [1 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0) should be [1 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.3) should be [1 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.5) should be [1 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.6) should be [1 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 0] to [1 / 1] at (1) should be [1 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 0] to [1 / 1] at (1.5) should be [1 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 0] to [1 / 1] at (-0.3) should be [1 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0) should be [1 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.3) should be [1 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.5) should be [1 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.6) should be [1 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 0] to [1 / 1] at (1) should be [1 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 0] to [1 / 1] at (1.5) should be [1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (-0.3) should be [1 / 0]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0) should be [1 / 0]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.3) should be [1 / 0]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.5) should be [1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.6) should be [1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (1) should be [1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (1.5) should be [1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (-0.3) should be [1 / 0]
+Pass	Web Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0) should be [1 / 0]
+Pass	Web Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.3) should be [1 / 0]
+Pass	Web Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.5) should be [1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (0.6) should be [1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (1) should be [1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 0] to [1 / 1] at (1.5) should be [1 / 1]
+Fail	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (-0.3) should be [1 / 1]
+Fail	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0) should be [1 / 1]
+Fail	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.3) should be [1 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.5) should be [0 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.6) should be [0 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (1) should be [0 / 1]
+Pass	CSS Transitions with transition-behavior:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (1.5) should be [0 / 1]
+Fail	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (-0.3) should be [1 / 1]
+Fail	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0) should be [1 / 1]
+Fail	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.3) should be [1 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.5) should be [0 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.6) should be [0 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (1) should be [0 / 1]
+Pass	CSS Transitions with transition-property:all and transition-behavor:allow-discrete: property <aspect-ratio> from [1 / 1] to [0 / 1] at (1.5) should be [0 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 1] to [0 / 1] at (-0.3) should be [0 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0) should be [0 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.3) should be [0 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.5) should be [0 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.6) should be [0 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 1] to [0 / 1] at (1) should be [0 / 1]
+Pass	CSS Transitions: property <aspect-ratio> from [1 / 1] to [0 / 1] at (1.5) should be [0 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 1] to [0 / 1] at (-0.3) should be [0 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0) should be [0 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.3) should be [0 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.5) should be [0 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.6) should be [0 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 1] to [0 / 1] at (1) should be [0 / 1]
+Pass	CSS Transitions with transition: all: property <aspect-ratio> from [1 / 1] to [0 / 1] at (1.5) should be [0 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (-0.3) should be [1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0) should be [1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.3) should be [1 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.5) should be [0 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.6) should be [0 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (1) should be [0 / 1]
+Pass	CSS Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (1.5) should be [0 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (-0.3) should be [1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0) should be [1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.3) should be [1 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.5) should be [0 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (0.6) should be [0 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (1) should be [0 / 1]
+Pass	Web Animations: property <aspect-ratio> from [1 / 1] to [0 / 1] at (1.5) should be [0 / 1]
+Pass	Compositing: property <aspect-ratio> underlying [2 / 1] from replace [0.5 / 1] to add [1 / 1] at (0) should be [0.5 / 1]
+Fail	Compositing: property <aspect-ratio> underlying [2 / 1] from replace [0.5 / 1] to add [1 / 1] at (0.5) should be [1 / 1]
+Fail	Compositing: property <aspect-ratio> underlying [2 / 1] from replace [0.5 / 1] to add [1 / 1] at (1) should be [2 / 1]
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/input/wpt-import/css/css-sizing/animation/aspect-ratio-interpolation.html b/Tests/LibWeb/Text/input/wpt-import/css/css-sizing/animation/aspect-ratio-interpolation.html
new file mode 100644
index 00000000000..980767f7195
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/css/css-sizing/animation/aspect-ratio-interpolation.html
@@ -0,0 +1,130 @@
+<!DOCTYPE html>
+<meta charset="UTF-8">
+<title>aspect-ratio interpolation</title>
+<link rel="help" href="https://drafts.csswg.org/css-sizing-4/#aspect-ratio">
+<meta name="assert" content="aspect-ratio supports animation">
+
+<script src="../../../resources/testharness.js"></script>
+<script src="../../../resources/testharnessreport.js"></script>
+<script src="../../../css/support/interpolation-testcommon.js"></script>
+
+<style>
+.target {
+  font-size: 16px;
+  background-color: black;
+  width: 10px;
+  aspect-ratio: 0.5;
+}
+</style>
+
+<body>
+  <template id="target-template">
+    <div class="container">
+      <div class="target"></div>
+    </div>
+  </template>
+</body>
+
+<script>
+test_interpolation({
+  property: 'aspect-ratio',
+  from: '0.5',
+  to: '2',
+}, [
+  {at: -0.5, expect: '0.25 / 1'},
+  {at: 0, expect: '0.5 / 1'},
+  {at: 0.5, expect: '1 / 1'},
+  {at: 1, expect: '2 / 1'},
+  {at: 1.5, expect: '4 / 1'}
+]);
+
+test_interpolation({
+  property: 'aspect-ratio',
+  from: '1 / 2',
+  to: '2 / 1',
+}, [
+  {at: -0.5, expect: '0.25 / 1'},
+  {at: 0, expect: '0.5 / 1'},
+  {at: 0.5, expect: '1 / 1'},
+  {at: 1, expect: '2 / 1'},
+  {at: 1.5, expect: '4 / 1'}
+]);
+
+// Test neutral keyframe
+test_interpolation({
+  property: 'aspect-ratio',
+  from: '',
+  to: '2 / 1',
+}, [
+  {at: -0.5, expect: '0.25 / 1'},
+  {at: 0, expect: '0.5 / 1'},
+  {at: 0.5, expect: '1 / 1'},
+  {at: 1, expect: '2 / 1'},
+  {at: 1.5, expect: '4 / 1'}
+]);
+
+test_interpolation({
+  property: 'aspect-ratio',
+  from: 'auto 1 / 2',
+  to: 'auto 2 / 1',
+}, [
+  {at: -0.5, expect: 'auto 0.25 / 1'},
+  {at: 0, expect: 'auto 0.5 / 1'},
+  {at: 0.5, expect: 'auto 1 / 1'},
+  {at: 1, expect: 'auto 2 / 1'},
+  {at: 1.5, expect: 'auto 4 / 1'}
+]);
+
+test_no_interpolation({
+  property: 'aspect-ratio',
+  from: 'auto',
+  to: '2 / 1',
+});
+
+test_no_interpolation({
+  property: 'aspect-ratio',
+  from: 'auto 1 / 1',
+  to: '2 / 1',
+});
+
+// If either number in the ratio is 0 or infinite, it represents a degenerate
+// ratio and will not be interpolated:
+// https://drafts.csswg.org/css-values-4/#combine-ratio
+test_no_interpolation({
+  property: 'aspect-ratio',
+  from: '1 / 0',
+  to: '1 / 1',
+});
+test_no_interpolation({
+  property: 'aspect-ratio',
+  from: '1 / 1',
+  to: '0 / 1',
+});
+
+// Addition of <ratio>s is not possible.
+// https://drafts.csswg.org/css-values/#combine-ratio
+//
+// And if a value type does not define a specific procedure for addition or is
+// defined as not additive, its addition operation is simply Vresult = Va.
+// (The first value is Va, the second value is Vb, and the result is Vresult.)
+// https://drafts.csswg.org/css-values-4/#not-additive,
+//
+// So in this test case:
+// 1. The 1st keyframe: { aspectRatio: 0.5/1, composite: 'replace', offset: 0 }
+// 2. The 2nd keyframe: { aspectRatio:   1/1, composite: 'add',     offset: 1 }
+// and the underlying value is 2/1. Based on the spec, the composited from_value
+// is 0.5/1 (because we just replace it), and the composited to_value is 2/1
+// (because we use Va as the result value).
+test_composition({
+  property: 'aspect-ratio',
+  underlying: '2 / 1',
+  replaceFrom: '0.5 / 1',
+  addTo: '1 / 1',
+}, [
+  {at: 0, expect: '0.5 / 1'},
+  {at: 0.5, expect: '1 / 1'},
+  {at: 1, expect: '2 / 1'}
+]);
+
+</script>
+</body>