diff --git a/components/layout_2020/flow/mod.rs b/components/layout_2020/flow/mod.rs
index 8bda0c69d24..d7b9854668a 100644
--- a/components/layout_2020/flow/mod.rs
+++ b/components/layout_2020/flow/mod.rs
@@ -20,7 +20,8 @@ use rayon::iter::{IndexedParallelIterator, IntoParallelRefIterator, ParallelIter
 use rayon_croissant::ParallelIteratorExt;
 use servo_arc::Arc;
 use style::properties::ComputedValues;
-use style::values::computed::{Length, LengthOrAuto};
+use style::values::computed::{Length, LengthOrAuto, LengthPercentage, LengthPercentageOrAuto};
+use style::values::generics::length::MaxSize;
 use style::Zero;
 
 mod construct;
@@ -355,27 +356,59 @@ fn layout_in_flow_non_replaced_block_level<'a>(
     let cbis = containing_block.inline_size;
     let padding = style.padding().percentages_relative_to(cbis);
     let border = style.border_width();
-    let mut computed_margin = style.margin().percentages_relative_to(cbis);
+    let margin = style.margin().percentages_relative_to(cbis);
     let pb = &padding + &border;
-    let box_size = style.box_size();
-    let inline_size = box_size.inline.percentage_relative_to(cbis);
-    if let LengthOrAuto::LengthPercentage(is) = inline_size {
-        let (margin_inline_start, margin_inline_end) = solve_inline_margins_for_in_flow_block_level(
+    let pb_inline_sum = pb.inline_sum();
+
+    let box_size = percent_resolved_box_size(style.box_size(), containing_block);
+    let max_box_size = percent_resolved_max_box_size(style.max_box_size(), containing_block);
+    let min_box_size =
+        percent_resolved_box_size(style.min_box_size(), containing_block).auto_is(Length::zero);
+
+    // https://drafts.csswg.org/css2/visudet.html#min-max-widths
+    let solve_inline_margins = |inline_size| {
+        solve_inline_margins_for_in_flow_block_level(
             containing_block,
-            pb.inline_sum(),
-            computed_margin.inline_start,
-            computed_margin.inline_end,
-            is,
-        );
-        computed_margin.inline_start = LengthOrAuto::LengthPercentage(margin_inline_start);
-        computed_margin.inline_end = LengthOrAuto::LengthPercentage(margin_inline_end);
+            pb_inline_sum,
+            margin.inline_start,
+            margin.inline_end,
+            inline_size,
+        )
+    };
+    let (mut inline_size, mut inline_margins) =
+        if let Some(inline_size) = box_size.inline.non_auto() {
+            (inline_size, solve_inline_margins(inline_size))
+        } else {
+            let margin_inline_start = margin.inline_start.auto_is(Length::zero);
+            let margin_inline_end = margin.inline_end.auto_is(Length::zero);
+            let margin_inline_sum = margin_inline_start + margin_inline_end;
+            let inline_size = cbis - pb_inline_sum - margin_inline_sum;
+            (inline_size, (margin_inline_start, margin_inline_end))
+        };
+    if let Some(max_inline_size) = max_box_size.inline {
+        if inline_size > max_inline_size {
+            inline_size = max_inline_size;
+            inline_margins = solve_inline_margins(inline_size);
+        }
     }
-    let margin = computed_margin.auto_is(Length::zero);
-    let mut block_margins_collapsed_with_children = CollapsedBlockMargins::from_margin(&margin);
-    let inline_size = inline_size.auto_is(|| cbis - pb.inline_sum() - margin.inline_sum());
-    let block_size = box_size
-        .block
-        .maybe_percentage_relative_to(containing_block.block_size.non_auto());
+    if inline_size < min_box_size.inline {
+        inline_size = min_box_size.inline;
+        inline_margins = solve_inline_margins(inline_size);
+    }
+
+    let margin = Sides {
+        inline_start: inline_margins.0,
+        inline_end: inline_margins.1,
+        block_start: margin.block_start.auto_is(Length::zero),
+        block_end: margin.block_end.auto_is(Length::zero),
+    };
+
+    // https://drafts.csswg.org/css2/visudet.html#min-max-heights
+    let mut block_size = box_size.block;
+    if let LengthOrAuto::LengthPercentage(ref mut block_size) = block_size {
+        *block_size = clamp_between_extremums(*block_size, min_box_size.block, max_box_size.block);
+    }
+
     let containing_block_for_children = ContainingBlock {
         inline_size,
         block_size,
@@ -386,16 +419,15 @@ fn layout_in_flow_non_replaced_block_level<'a>(
         containing_block.mode, containing_block_for_children.mode,
         "Mixed writing modes are not supported yet"
     );
+
     let this_start_margin_can_collapse_with_children = CollapsibleWithParentStartMargin(
         block_level_kind == BlockLevelKind::SameFormattingContextBlock &&
             pb.block_start == Length::zero(),
     );
-    let this_end_margin_can_collapse_with_children = (block_level_kind, pb.block_end, block_size) ==
-        (
-            BlockLevelKind::SameFormattingContextBlock,
-            Length::zero(),
-            LengthOrAuto::Auto,
-        );
+    let this_end_margin_can_collapse_with_children = block_size == LengthOrAuto::Auto &&
+        min_box_size.block == Length::zero() &&
+        pb.block_end == Length::zero() &&
+        block_level_kind == BlockLevelKind::SameFormattingContextBlock;
     let mut nested_abspos = vec![];
     let mut flow_layout = layout_contents(
         &containing_block_for_children,
@@ -406,6 +438,7 @@ fn layout_in_flow_non_replaced_block_level<'a>(
         },
         this_start_margin_can_collapse_with_children,
     );
+    let mut block_margins_collapsed_with_children = CollapsedBlockMargins::from_margin(&margin);
     if this_start_margin_can_collapse_with_children.0 {
         block_margins_collapsed_with_children
             .start
@@ -436,7 +469,13 @@ fn layout_in_flow_non_replaced_block_level<'a>(
                 .collapsible_margins_in_children
                 .collapsed_through;
     let relative_adjustement = relative_adjustement(style, inline_size, block_size);
-    let block_size = block_size.auto_is(|| flow_layout.content_block_size);
+    let block_size = block_size.auto_is(|| {
+        clamp_between_extremums(
+            flow_layout.content_block_size,
+            min_box_size.block,
+            max_box_size.block,
+        )
+    });
     let content_rect = Rect {
         start_corner: Vec2 {
             block: pb.block_start + relative_adjustement.block,
@@ -486,23 +525,124 @@ fn layout_in_flow_replaced_block_level<'a>(
     let intrinsic_size = replaced.intrinsic_size.size_to_flow_relative(mode);
     // FIXME(nox): This can divide by zero.
     let intrinsic_ratio = intrinsic_size.inline.px() / intrinsic_size.block.px();
-    let box_size = style.box_size();
-    let inline_size = box_size.inline.percentage_relative_to(cbis);
-    let block_size = box_size
-        .block
-        .maybe_percentage_relative_to(containing_block.block_size.non_auto());
-    let (inline_size, block_size) = match (inline_size, block_size) {
+
+    let box_size = percent_resolved_box_size(style.box_size(), containing_block);
+    let min_box_size =
+        percent_resolved_box_size(style.min_box_size(), containing_block).auto_is(Length::zero);
+    let max_box_size = percent_resolved_max_box_size(style.max_box_size(), containing_block);
+
+    let clamp = |inline_size, block_size| {
+        (
+            clamp_between_extremums(inline_size, min_box_size.inline, max_box_size.inline),
+            clamp_between_extremums(block_size, min_box_size.block, max_box_size.block),
+        )
+    };
+    // https://drafts.csswg.org/css2/visudet.html#min-max-widths
+    // https://drafts.csswg.org/css2/visudet.html#min-max-heights
+    let (inline_size, block_size) = match (box_size.inline, box_size.block) {
         (LengthOrAuto::LengthPercentage(inline), LengthOrAuto::LengthPercentage(block)) => {
-            (inline, block)
+            clamp(inline, block)
         },
         (LengthOrAuto::LengthPercentage(inline), LengthOrAuto::Auto) => {
-            (inline, inline / intrinsic_ratio)
+            clamp(inline, inline / intrinsic_ratio)
         },
         (LengthOrAuto::Auto, LengthOrAuto::LengthPercentage(block)) => {
-            (block * intrinsic_ratio, block)
+            clamp(block * intrinsic_ratio, block)
+        },
+        (LengthOrAuto::Auto, LengthOrAuto::Auto) => {
+            enum Violation {
+                None,
+                Below(Length),
+                Above(Length),
+            }
+            let violation = |size, min_size, mut max_size: Option<Length>| {
+                if let Some(max) = max_size.as_mut() {
+                    max.max_assign(min_size);
+                }
+                if size < min_size {
+                    return Violation::Below(min_size);
+                }
+                match max_size {
+                    Some(max_size) if size > max_size => Violation::Above(max_size),
+                    _ => Violation::None,
+                }
+            };
+            match (
+                violation(
+                    intrinsic_size.inline,
+                    min_box_size.inline,
+                    max_box_size.inline,
+                ),
+                violation(intrinsic_size.block, min_box_size.block, max_box_size.block),
+            ) {
+                // Row 1.
+                (Violation::None, Violation::None) => (intrinsic_size.inline, intrinsic_size.block),
+                // Row 2.
+                (Violation::Above(max_inline_size), Violation::None) => {
+                    let block_size = (max_inline_size / intrinsic_ratio).max(min_box_size.block);
+                    (max_inline_size, block_size)
+                },
+                // Row 3.
+                (Violation::Below(min_inline_size), Violation::None) => {
+                    let block_size =
+                        clamp_below_max(min_inline_size / intrinsic_ratio, max_box_size.block);
+                    (min_inline_size, block_size)
+                },
+                // Row 4.
+                (Violation::None, Violation::Above(max_block_size)) => {
+                    let inline_size = (max_block_size * intrinsic_ratio).max(min_box_size.inline);
+                    (inline_size, max_block_size)
+                },
+                // Row 5.
+                (Violation::None, Violation::Below(min_block_size)) => {
+                    let inline_size =
+                        clamp_below_max(min_block_size * intrinsic_ratio, max_box_size.inline);
+                    (inline_size, min_block_size)
+                },
+                // Rows 6-7.
+                (Violation::Above(max_inline_size), Violation::Above(max_block_size)) => {
+                    if max_inline_size.px() / intrinsic_size.inline.px() <=
+                        max_block_size.px() / intrinsic_size.block.px()
+                    {
+                        // Row 6.
+                        let block_size =
+                            (max_inline_size / intrinsic_ratio).max(min_box_size.block);
+                        (max_inline_size, block_size)
+                    } else {
+                        // Row 7.
+                        let inline_size =
+                            (max_block_size * intrinsic_ratio).max(min_box_size.inline);
+                        (inline_size, max_block_size)
+                    }
+                },
+                // Rows 8-9.
+                (Violation::Below(min_inline_size), Violation::Below(min_block_size)) => {
+                    if min_inline_size.px() / intrinsic_size.inline.px() <=
+                        min_block_size.px() / intrinsic_size.block.px()
+                    {
+                        // Row 8.
+                        let inline_size =
+                            clamp_below_max(min_block_size * intrinsic_ratio, max_box_size.inline);
+                        (inline_size, min_block_size)
+                    } else {
+                        // Row 9.
+                        let block_size =
+                            clamp_below_max(min_inline_size / intrinsic_ratio, max_box_size.block);
+                        (min_inline_size, block_size)
+                    }
+                },
+                // Row 10.
+                (Violation::Below(min_inline_size), Violation::Above(max_block_size)) => {
+                    (min_inline_size, max_block_size)
+                },
+                // Row 11.
+                (Violation::Above(max_inline_size), Violation::Below(min_block_size)) => {
+                    (max_inline_size, min_block_size)
+                },
+            }
         },
-        (LengthOrAuto::Auto, LengthOrAuto::Auto) => (intrinsic_size.inline, intrinsic_size.block),
     };
+
     let (margin_inline_start, margin_inline_end) = solve_inline_margins_for_in_flow_block_level(
         containing_block,
         pb.inline_sum(),
@@ -567,3 +707,45 @@ fn solve_inline_margins_for_in_flow_block_level(
         (LengthOrAuto::LengthPercentage(start), _) => (start, inline_margins - start),
     }
 }
+
+fn clamp_between_extremums(size: Length, min_size: Length, max_size: Option<Length>) -> Length {
+    clamp_below_max(size, max_size).max(min_size)
+}
+
+fn clamp_below_max(size: Length, max_size: Option<Length>) -> Length {
+    max_size.map_or(size, |max_size| size.min(max_size))
+}
+
+fn percent_resolved_box_size(
+    box_size: Vec2<LengthPercentageOrAuto>,
+    containing_block: &ContainingBlock,
+) -> Vec2<LengthOrAuto> {
+    Vec2 {
+        inline: box_size
+            .inline
+            .percentage_relative_to(containing_block.inline_size),
+        block: box_size
+            .block
+            .maybe_percentage_relative_to(containing_block.block_size.non_auto()),
+    }
+}
+
+fn percent_resolved_max_box_size(
+    max_box_size: Vec2<MaxSize<LengthPercentage>>,
+    containing_block: &ContainingBlock,
+) -> Vec2<Option<Length>> {
+    Vec2 {
+        inline: match max_box_size.inline {
+            MaxSize::LengthPercentage(max_inline_size) => {
+                Some(max_inline_size.percentage_relative_to(containing_block.inline_size))
+            },
+            MaxSize::None => None,
+        },
+        block: match max_box_size.block {
+            MaxSize::LengthPercentage(max_block_size) => {
+                max_block_size.maybe_percentage_relative_to(containing_block.block_size.non_auto())
+            },
+            MaxSize::None => None,
+        },
+    }
+}
diff --git a/components/layout_2020/geom.rs b/components/layout_2020/geom.rs
index d75a1634561..39c7cb331e4 100644
--- a/components/layout_2020/geom.rs
+++ b/components/layout_2020/geom.rs
@@ -141,6 +141,15 @@ impl flow_relative::Vec2<Length> {
     }
 }
 
+impl flow_relative::Vec2<LengthOrAuto> {
+    pub fn auto_is(&self, f: impl Fn() -> Length) -> flow_relative::Vec2<Length> {
+        flow_relative::Vec2 {
+            inline: self.inline.auto_is(&f),
+            block: self.block.auto_is(&f),
+        }
+    }
+}
+
 impl flow_relative::Rect<Length> {
     pub fn zero() -> Self {
         Self {
diff --git a/components/layout_2020/style_ext.rs b/components/layout_2020/style_ext.rs
index e6d4537f47c..8c145f23c6f 100644
--- a/components/layout_2020/style_ext.rs
+++ b/components/layout_2020/style_ext.rs
@@ -4,7 +4,9 @@
 
 use crate::geom::{flow_relative, physical};
 use style::properties::ComputedValues;
-use style::values::computed::{Length, LengthPercentage, LengthPercentageOrAuto, Size};
+use style::values::computed::{Length, LengthPercentage, LengthPercentageOrAuto};
+use style::values::computed::{NonNegativeLengthPercentage, Size};
+use style::values::generics::length::MaxSize;
 use style::values::specified::box_ as stylo;
 
 pub use style::computed_values::direction::T as Direction;
@@ -45,6 +47,8 @@ pub(crate) trait ComputedValuesExt {
     fn writing_mode(&self) -> (WritingMode, Direction);
     fn box_offsets(&self) -> flow_relative::Sides<LengthPercentageOrAuto>;
     fn box_size(&self) -> flow_relative::Vec2<LengthPercentageOrAuto>;
+    fn min_box_size(&self) -> flow_relative::Vec2<LengthPercentageOrAuto>;
+    fn max_box_size(&self) -> flow_relative::Vec2<MaxSize<LengthPercentage>>;
     fn padding(&self) -> flow_relative::Sides<LengthPercentage>;
     fn border_width(&self) -> flow_relative::Sides<Length>;
     fn margin(&self) -> flow_relative::Sides<LengthPercentageOrAuto>;
@@ -80,6 +84,30 @@ impl ComputedValuesExt for ComputedValues {
         .size_to_flow_relative(self.writing_mode())
     }
 
+    #[inline]
+    fn min_box_size(&self) -> flow_relative::Vec2<LengthPercentageOrAuto> {
+        let position = self.get_position();
+        physical::Vec2 {
+            x: size_to_length(position.min_width),
+            y: size_to_length(position.min_height),
+        }
+        .size_to_flow_relative(self.writing_mode())
+    }
+
+    #[inline]
+    fn max_box_size(&self) -> flow_relative::Vec2<MaxSize<LengthPercentage>> {
+        let unwrap = |max_size: MaxSize<NonNegativeLengthPercentage>| match max_size {
+            MaxSize::LengthPercentage(length) => MaxSize::LengthPercentage(length.0),
+            MaxSize::None => MaxSize::None,
+        };
+        let position = self.get_position();
+        physical::Vec2 {
+            x: unwrap(position.max_width),
+            y: unwrap(position.max_height),
+        }
+        .size_to_flow_relative(self.writing_mode())
+    }
+
     #[inline]
     fn padding(&self) -> flow_relative::Sides<LengthPercentage> {
         let padding = self.get_padding();
diff --git a/components/style/properties/longhands/position.mako.rs b/components/style/properties/longhands/position.mako.rs
index 95595f36316..d974a0f5915 100644
--- a/components/style/properties/longhands/position.mako.rs
+++ b/components/style/properties/longhands/position.mako.rs
@@ -289,7 +289,6 @@ ${helpers.predefined_type(
         "Size",
         "computed::Size::auto()",
         engines="gecko servo-2013 servo-2020",
-        servo_2020_pref="layout.2020.unimplemented",
         logical=logical,
         logical_group="min-size",
         allow_quirks="No" if logical else "Yes",
@@ -302,7 +301,6 @@ ${helpers.predefined_type(
         "MaxSize",
         "computed::MaxSize::none()",
         engines="gecko servo-2013 servo-2020",
-        servo_2020_pref="layout.2020.unimplemented",
         logical=logical,
         logical_group="max-size",
         allow_quirks="No" if logical else "Yes",