diff --git a/Base/res/html/misc/flex.html b/Base/res/html/misc/flex.html
index 33b380f43f..a487eb1e16 100644
--- a/Base/res/html/misc/flex.html
+++ b/Base/res/html/misc/flex.html
@@ -154,6 +154,68 @@
         <div class="box" style="flex-shrink: 1;">2 I shrink</div>
         <div class="box" style="flex-shrink: 0;">3 I don't</div>
     </div>
+
+    <h2>Flex shorthand</h2>
+    <p>flex: initial;</p>
+    <div class="my-container" style="width: 500px;">
+        <div class="box" style="flex: initial;">1</div>
+        <div class="box" style="flex: initial;">2</div>
+        <div class="box" style="flex: initial;">3</div>
+    </div>
+    <p>flex: auto;</p>
+    <div class="my-container" style="width: 500px;">
+        <div class="box" style="flex: auto;">1</div>
+        <div class="box" style="flex: auto;">2</div>
+        <div class="box" style="flex: auto;">3</div>
+    </div>
+    <p>flex: none;</p>
+    <div class="my-container" style="width: 500px;">
+        <div class="box" style="flex: none;">1</div>
+        <div class="box" style="flex: none;">2</div>
+        <div class="box" style="flex: none;">3</div>
+    </div>
+    <p>flex: 1/2/3;</p>
+    <div class="my-container" style="width: 500px;">
+        <div class="box" style="flex: 1;">1</div>
+        <div class="box" style="flex: 2;">2</div>
+        <div class="box" style="flex: 3;">3</div>
+    </div>
+    <p>flex: 0 0 0;</p>
+    <div class="my-container" style="width: 500px;">
+        <div class="box" style="flex: 0 0 0;">1</div>
+        <div class="box" style="flex: 0 0 0;">2</div>
+        <div class="box" style="flex: 0 0 0;">3</div>
+    </div>
+    <p>flex: 1 2 0;</p>
+    <div class="my-container" style="width: 500px;">
+        <div class="box" style="flex: 1 2 0;">1</div>
+        <div class="box" style="flex: 1 2 0;">2</div>
+        <div class="box" style="flex: 1 2 0;">3</div>
+    </div>
+    <p>flex: 0 1 2; <span style="color: red;">(Invalid)</span></p>
+    <div class="my-container" style="width: 500px;">
+        <div class="box" style="flex: 0 1 2;">1</div>
+        <div class="box" style="flex: 0 1 2;">2</div>
+        <div class="box" style="flex: 0 1 2;">3</div>
+    </div>
+    <p>flex: 4/1/0 0 50px;</p>
+    <div class="my-container" style="width: 500px;">
+        <div class="box" style="flex: 4 0 50px;">1</div>
+        <div class="box" style="flex: 1 0 50px;">2</div>
+        <div class="box" style="flex: 0 0 50px;">3</div>
+    </div>
+    <p>flex: 80% 0 4/1/0;</p>
+    <div class="my-container" style="width: 500px;">
+        <div class="box" style="flex: 80% 0 4;">1</div>
+        <div class="box" style="flex: 80% 0 1;">2</div>
+        <div class="box" style="flex: 80% 0 0;">3</div>
+    </div>
+    <p>flex: auto 0 4/1/0;</p>
+    <div class="my-container" style="width: 500px;">
+        <div class="box" style="flex: auto 0 4;">1</div>
+        <div class="box" style="flex: auto 0 1;">2</div>
+        <div class="box" style="flex: auto 0 0;">3</div>
+    </div>
 </body>
 
 </html>
diff --git a/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp b/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
index 06a3135178..3e7c092c09 100644
--- a/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
+++ b/Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
@@ -1889,6 +1889,98 @@ RefPtr<StyleValue> Parser::parse_box_shadow_value(ParsingContext const& context,
     return BoxShadowStyleValue::create(offset_x, offset_y, blur_radius, color);
 }
 
+RefPtr<StyleValue> Parser::parse_flex_value(ParsingContext const& context, Vector<StyleComponentValueRule> const& component_values)
+{
+    auto is_flex_grow_or_shrink = [](StyleValue const& value) -> bool {
+        if (value.is_numeric())
+            return true;
+        return false;
+    };
+
+    auto is_flex_basis = [](StyleValue const& value) -> bool {
+        if (value.is_length())
+            return true;
+        switch (value.to_identifier()) {
+        case ValueID::Auto:
+        case ValueID::Content:
+            return true;
+        default:
+            return false;
+        }
+    };
+
+    if (component_values.size() == 1) {
+        auto value = parse_css_value(context, PropertyID::Flex, component_values[0]);
+        if (!value)
+            return nullptr;
+
+        switch (value->to_identifier()) {
+        case ValueID::Auto: {
+            auto one = NumericStyleValue::create(1);
+            return FlexStyleValue::create(one, one, IdentifierStyleValue::create(ValueID::Auto));
+        }
+        case ValueID::None: {
+            auto zero = NumericStyleValue::create(0);
+            return FlexStyleValue::create(zero, zero, IdentifierStyleValue::create(ValueID::Auto));
+        }
+        default:
+            break;
+        }
+    }
+
+    RefPtr<StyleValue> flex_grow;
+    RefPtr<StyleValue> flex_shrink;
+    RefPtr<StyleValue> flex_basis;
+
+    for (size_t i = 0; i < component_values.size(); ++i) {
+        auto value = parse_css_value(context, PropertyID::Flex, component_values[i]);
+        if (!value)
+            return nullptr;
+
+        // Zero is a valid value for basis, but only if grow and shrink are already specified.
+        if (value->is_numeric() && static_cast<NumericStyleValue&>(*value).value() == 0) {
+            if (flex_grow && flex_shrink && !flex_basis) {
+                flex_basis = LengthStyleValue::create(Length(0, Length::Type::Px));
+                continue;
+            }
+        }
+
+        if (is_flex_grow_or_shrink(*value)) {
+            if (flex_grow)
+                return nullptr;
+            flex_grow = value.release_nonnull();
+
+            // Flex-shrink may optionally follow directly after.
+            if (i + 1 < component_values.size()) {
+                auto second_value = parse_css_value(context, PropertyID::Flex, component_values[i + 1]);
+                if (second_value && is_flex_grow_or_shrink(*second_value)) {
+                    flex_shrink = second_value.release_nonnull();
+                    i++;
+                }
+            }
+            continue;
+        }
+
+        if (is_flex_basis(*value)) {
+            if (flex_basis)
+                return nullptr;
+            flex_basis = value.release_nonnull();
+            continue;
+        }
+
+        return nullptr;
+    }
+
+    if (!flex_grow)
+        flex_grow = NumericStyleValue::create(0);
+    if (!flex_shrink)
+        flex_shrink = NumericStyleValue::create(1);
+    if (!flex_basis)
+        flex_basis = IdentifierStyleValue::create(ValueID::Auto);
+
+    return FlexStyleValue::create(flex_grow.release_nonnull(), flex_shrink.release_nonnull(), flex_basis.release_nonnull());
+}
+
 RefPtr<StyleValue> Parser::parse_font_value(ParsingContext const& context, Vector<StyleComponentValueRule> const& component_values)
 {
     auto is_font_size = [](StyleValue const& value) -> bool {
@@ -2285,6 +2377,10 @@ RefPtr<StyleValue> Parser::parse_css_value(PropertyID property_id, TokenStream<S
         if (auto parsed_box_shadow = parse_box_shadow_value(m_context, component_values))
             return parsed_box_shadow;
         break;
+    case PropertyID::Flex:
+        if (auto parsed_value = parse_flex_value(m_context, component_values))
+            return parsed_value;
+        break;
     case PropertyID::Font:
         if (auto parsed_value = parse_font_value(m_context, component_values))
             return parsed_value;
diff --git a/Userland/Libraries/LibWeb/CSS/Parser/Parser.h b/Userland/Libraries/LibWeb/CSS/Parser/Parser.h
index f620e2fde1..dc614ee058 100644
--- a/Userland/Libraries/LibWeb/CSS/Parser/Parser.h
+++ b/Userland/Libraries/LibWeb/CSS/Parser/Parser.h
@@ -177,6 +177,7 @@ private:
     static RefPtr<StyleValue> parse_image_value(ParsingContext const&, StyleComponentValueRule const&);
     static RefPtr<StyleValue> parse_background_value(ParsingContext const&, Vector<StyleComponentValueRule> const&);
     static RefPtr<StyleValue> parse_box_shadow_value(ParsingContext const&, Vector<StyleComponentValueRule> const&);
+    static RefPtr<StyleValue> parse_flex_value(ParsingContext const&, Vector<StyleComponentValueRule> const&);
     static RefPtr<StyleValue> parse_font_value(ParsingContext const&, Vector<StyleComponentValueRule> const&);
     static RefPtr<StyleValue> parse_list_style_value(ParsingContext const&, Vector<StyleComponentValueRule> const&);
     static RefPtr<StyleValue> parse_text_decoration_value(ParsingContext const&, Vector<StyleComponentValueRule> const&);
diff --git a/Userland/Libraries/LibWeb/CSS/StyleResolver.cpp b/Userland/Libraries/LibWeb/CSS/StyleResolver.cpp
index 387b0308e9..32720bd4a9 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleResolver.cpp
+++ b/Userland/Libraries/LibWeb/CSS/StyleResolver.cpp
@@ -250,31 +250,6 @@ static inline bool is_flex_wrap(StyleValue const& value)
     }
 }
 
-static inline bool is_flex_grow_or_shrink(StyleValue const& value)
-{
-    if (value.is_builtin_or_dynamic())
-        return true;
-
-    if (value.is_numeric())
-        return true;
-
-    return false;
-}
-
-static inline bool is_flex_basis(StyleValue const& value)
-{
-    if (value.is_builtin_or_dynamic())
-        return true;
-
-    if (value.is_length())
-        return true;
-
-    if (value.is_identifier() && value.to_identifier() == ValueID::Content)
-        return true;
-
-    return false;
-}
-
 static inline bool is_font_family(StyleValue const& value)
 {
     if (value.is_builtin_or_dynamic())
@@ -801,61 +776,19 @@ static void set_property_expanding_shorthands(StyleProperties& style, CSS::Prope
     }
 
     if (property_id == CSS::PropertyID::Flex) {
-        if (value.is_length() || (value.is_identifier() && value.to_identifier() == CSS::ValueID::Content)) {
+        if (value.is_flex()) {
+            auto& flex = static_cast<CSS::FlexStyleValue const&>(value);
+            style.set_property(CSS::PropertyID::FlexGrow, flex.grow());
+            style.set_property(CSS::PropertyID::FlexShrink, flex.shrink());
+            style.set_property(CSS::PropertyID::FlexBasis, flex.basis());
+            return;
+        }
+        if (value.is_builtin()) {
+            style.set_property(CSS::PropertyID::FlexGrow, value);
+            style.set_property(CSS::PropertyID::FlexShrink, value);
             style.set_property(CSS::PropertyID::FlexBasis, value);
             return;
         }
-
-        if (value.is_component_value_list()) {
-            auto parts = static_cast<CSS::ValueListStyleValue const&>(value).values();
-            if (parts.size() == 1) {
-                auto value = Parser::parse_css_value(context, property_id, parts[0]);
-                if (!value)
-                    return;
-                if (is_flex_basis(*value)) {
-                    style.set_property(CSS::PropertyID::FlexBasis, *value);
-                } else if (is_flex_grow_or_shrink(*value)) {
-                    style.set_property(CSS::PropertyID::FlexGrow, *value);
-                }
-                return;
-            }
-
-            if (parts.size() == 2) {
-                auto flex_grow = Parser::parse_css_value(context, property_id, parts[0]);
-                auto second_value = Parser::parse_css_value(context, property_id, parts[1]);
-                if (!flex_grow || !second_value)
-                    return;
-
-                style.set_property(CSS::PropertyID::FlexGrow, *flex_grow);
-
-                if (is_flex_basis(*second_value)) {
-                    style.set_property(CSS::PropertyID::FlexBasis, *second_value);
-                } else if (is_flex_grow_or_shrink(*second_value)) {
-                    style.set_property(CSS::PropertyID::FlexShrink, *second_value);
-                }
-                return;
-            }
-
-            if (parts.size() == 3) {
-                auto flex_grow = Parser::parse_css_value(context, property_id, parts[0]);
-                auto flex_shrink = Parser::parse_css_value(context, property_id, parts[1]);
-                auto flex_basis = Parser::parse_css_value(context, property_id, parts[2]);
-                if (!flex_grow || !flex_shrink || !flex_basis)
-                    return;
-
-                style.set_property(CSS::PropertyID::FlexGrow, *flex_grow);
-                style.set_property(CSS::PropertyID::FlexShrink, *flex_shrink);
-
-                if (is_flex_basis(*flex_basis))
-                    style.set_property(CSS::PropertyID::FlexBasis, *flex_basis);
-
-                return;
-            }
-
-            return;
-        }
-
-        dbgln("Unsure what to do with CSS flex value '{}'", value.to_string());
         return;
     }
 
diff --git a/Userland/Libraries/LibWeb/CSS/StyleValue.h b/Userland/Libraries/LibWeb/CSS/StyleValue.h
index bcbde3f97f..1699a36d58 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleValue.h
+++ b/Userland/Libraries/LibWeb/CSS/StyleValue.h
@@ -231,6 +231,7 @@ public:
         Calculated,
         Background,
         BoxShadow,
+        Flex,
         Font,
         ListStyle,
         TextDecoration,
@@ -252,6 +253,7 @@ public:
     bool is_calculated() const { return type() == Type::Calculated; }
     bool is_background() const { return type() == Type::Background; }
     bool is_box_shadow() const { return type() == Type::BoxShadow; }
+    bool is_flex() const { return type() == Type::Flex; }
     bool is_font() const { return type() == Type::Font; }
     bool is_list_style() const { return type() == Type::ListStyle; }
     bool is_text_decoration() const { return type() == Type::TextDecoration; }
@@ -677,6 +679,43 @@ private:
     // FIXME: background-origin
 };
 
+class FlexStyleValue final : public StyleValue {
+public:
+    static NonnullRefPtr<FlexStyleValue> create(
+        NonnullRefPtr<StyleValue> grow,
+        NonnullRefPtr<StyleValue> shrink,
+        NonnullRefPtr<StyleValue> basis)
+    {
+        return adopt_ref(*new FlexStyleValue(grow, shrink, basis));
+    }
+    virtual ~FlexStyleValue() override { }
+
+    NonnullRefPtr<StyleValue> grow() const { return m_grow; }
+    NonnullRefPtr<StyleValue> shrink() const { return m_shrink; }
+    NonnullRefPtr<StyleValue> basis() const { return m_basis; }
+
+    virtual String to_string() const override
+    {
+        return String::formatted("Flex grow: {}, shrink: {}, basis: {}", m_grow->to_string(), m_shrink->to_string(), m_basis->to_string());
+    }
+
+private:
+    FlexStyleValue(
+        NonnullRefPtr<StyleValue> grow,
+        NonnullRefPtr<StyleValue> shrink,
+        NonnullRefPtr<StyleValue> basis)
+        : StyleValue(Type::Flex)
+        , m_grow(grow)
+        , m_shrink(shrink)
+        , m_basis(basis)
+    {
+    }
+
+    NonnullRefPtr<StyleValue> m_grow;
+    NonnullRefPtr<StyleValue> m_shrink;
+    NonnullRefPtr<StyleValue> m_basis;
+};
+
 class FontStyleValue final : public StyleValue {
 public:
     static NonnullRefPtr<FontStyleValue> create(NonnullRefPtr<StyleValue> font_style, NonnullRefPtr<StyleValue> font_weight, NonnullRefPtr<StyleValue> font_size, NonnullRefPtr<StyleValue> line_height, NonnullRefPtrVector<StyleValue>&& font_families) { return adopt_ref(*new FontStyleValue(font_style, font_weight, font_size, line_height, move(font_families))); }