diff --git a/components/style/counter_style/mod.rs b/components/style/counter_style/mod.rs
index daad5145e1c..d968bf20d51 100644
--- a/components/style/counter_style/mod.rs
+++ b/components/style/counter_style/mod.rs
@@ -244,7 +244,7 @@ macro_rules! counter_style_descriptors {
                         dest.write_str("; ")?;
                     }
                 )+
-                dest.write_str("}")
+                dest.write_char('}')
             }
         }
     }
diff --git a/components/style/font_face.rs b/components/style/font_face.rs
index f1b4651c769..7ed545a1c4d 100644
--- a/components/style/font_face.rs
+++ b/components/style/font_face.rs
@@ -306,7 +306,7 @@ macro_rules! impl_range {
             {
                 self.0.to_css(dest)?;
                 if self.0 != self.1 {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                     self.1.to_css(dest)?;
                 }
                 Ok(())
@@ -714,7 +714,7 @@ impl ToCssWithGuard for FontFaceRuleData {
     fn to_css(&self, _guard: &SharedRwLockReadGuard, dest: &mut CssStringWriter) -> fmt::Result {
         dest.write_str("@font-face { ")?;
         self.decl_to_css(dest)?;
-        dest.write_str("}")
+        dest.write_char('}')
     }
 }
 
diff --git a/components/style/gecko_bindings/sugar/refptr.rs b/components/style/gecko_bindings/sugar/refptr.rs
index d8c0cea0f2b..e2536018622 100644
--- a/components/style/gecko_bindings/sugar/refptr.rs
+++ b/components/style/gecko_bindings/sugar/refptr.rs
@@ -11,6 +11,7 @@ use servo_arc::Arc;
 use std::marker::PhantomData;
 use std::ops::{Deref, DerefMut};
 use std::{fmt, mem, ptr};
+use std::fmt::Write;
 
 /// Trait for all objects that have Addref() and Release
 /// methods and can be placed inside RefPtr<T>
@@ -35,7 +36,7 @@ impl<T: RefCounted> fmt::Debug for RefPtr<T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         f.write_str("RefPtr { ")?;
         self.ptr.fmt(f)?;
-        f.write_str("}")
+        f.write_char('}')
     }
 }
 
diff --git a/components/style/invalidation/element/invalidator.rs b/components/style/invalidation/element/invalidator.rs
index ac8f9ed5f81..db644d1a449 100644
--- a/components/style/invalidation/element/invalidator.rs
+++ b/components/style/invalidation/element/invalidator.rs
@@ -14,6 +14,7 @@ use selectors::parser::{Combinator, Component};
 use selectors::OpaqueElement;
 use smallvec::SmallVec;
 use std::fmt;
+use std::fmt::Write;
 
 /// A trait to abstract the collection of invalidations for a given pass.
 pub trait InvalidationProcessor<'a, E>
@@ -257,7 +258,7 @@ impl<'a> fmt::Debug for Invalidation<'a> {
             }
             component.to_css(f)?;
         }
-        f.write_str(")")
+        f.write_char(')')
     }
 }
 
diff --git a/components/style/piecewise_linear.rs b/components/style/piecewise_linear.rs
index 9259a086bd2..84ccb7061c3 100644
--- a/components/style/piecewise_linear.rs
+++ b/components/style/piecewise_linear.rs
@@ -39,7 +39,7 @@ impl ToCss for PiecewiseLinearFunctionEntry {
         W: fmt::Write,
     {
         self.y.to_css(dest)?;
-        dest.write_str(" ")?;
+        dest.write_char(' ')?;
         Percentage(self.x).to_css(dest)
     }
 }
diff --git a/components/style/properties/declaration_block.rs b/components/style/properties/declaration_block.rs
index 01b390f0fca..204c874fc1c 100644
--- a/components/style/properties/declaration_block.rs
+++ b/components/style/properties/declaration_block.rs
@@ -1183,7 +1183,7 @@ where
     W: Write,
 {
     if !*is_first_serialization {
-        dest.write_str(" ")
+        dest.write_char(' ')
     } else {
         *is_first_serialization = false;
         Ok(())
diff --git a/components/style/properties/helpers.mako.rs b/components/style/properties/helpers.mako.rs
index 4c051ab550f..2bf274d32cc 100644
--- a/components/style/properties/helpers.mako.rs
+++ b/components/style/properties/helpers.mako.rs
@@ -865,7 +865,7 @@
 
             first.to_css(dest)?;
             if first != second {
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
                 second.to_css(dest)?;
             }
             Ok(())
diff --git a/components/style/properties/properties.mako.rs b/components/style/properties/properties.mako.rs
index 5c052bec73f..2587bd1987c 100644
--- a/components/style/properties/properties.mako.rs
+++ b/components/style/properties/properties.mako.rs
@@ -134,10 +134,10 @@ pub mod shorthands {
         width.to_css(dest)?;
         // FIXME(emilio): Should we really serialize the border style if it's
         // `solid`?
-        dest.write_str(" ")?;
+        dest.write_char(' ')?;
         style.to_css(dest)?;
         if *color != Color::CurrentColor {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             color.to_css(dest)?;
         }
         Ok(())
diff --git a/components/style/properties/shorthands/background.mako.rs b/components/style/properties/shorthands/background.mako.rs
index ff5edecff4d..5fee5cb2b03 100644
--- a/components/style/properties/shorthands/background.mako.rs
+++ b/components/style/properties/shorthands/background.mako.rs
@@ -167,7 +167,7 @@
 
                 if *image != background_image::single_value::get_initial_specified_value() {
                     if wrote_value {
-                        dest.write_str(" ")?;
+                        dest.write_char(' ')?;
                     }
                     image.to_css(dest)?;
                     wrote_value = true;
@@ -180,7 +180,7 @@
                     *size != background_size::single_value::get_initial_specified_value()
                 {
                     if wrote_value {
-                        dest.write_str(" ")?;
+                        dest.write_char(' ')?;
                     }
 
                     Position {
@@ -199,7 +199,7 @@
                 % for name in "repeat attachment".split():
                     if *${name} != background_${name}::single_value::get_initial_specified_value() {
                         if wrote_value {
-                            dest.write_str(" ")?;
+                            dest.write_char(' ')?;
                         }
                         ${name}.to_css(dest)?;
                         wrote_value = true;
@@ -208,11 +208,11 @@
 
                 if *origin != Origin::PaddingBox || *clip != Clip::BorderBox {
                     if wrote_value {
-                        dest.write_str(" ")?;
+                        dest.write_char(' ')?;
                     }
                     origin.to_css(dest)?;
                     if *clip != From::from(*origin) {
-                        dest.write_str(" ")?;
+                        dest.write_char(' ')?;
                         clip.to_css(dest)?;
                     }
 
diff --git a/components/style/properties/shorthands/border.mako.rs b/components/style/properties/shorthands/border.mako.rs
index 217d1a451f3..95dca014a64 100644
--- a/components/style/properties/shorthands/border.mako.rs
+++ b/components/style/properties/shorthands/border.mako.rs
@@ -373,13 +373,13 @@ pub fn parse_border<'i, 't>(
     impl<'a> ToCss for LonghandsToSerialize<'a>  {
         fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result where W: fmt::Write {
             self.border_image_source.to_css(dest)?;
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.border_image_slice.to_css(dest)?;
             dest.write_str(" / ")?;
             self.border_image_width.to_css(dest)?;
             dest.write_str(" / ")?;
             self.border_image_outset.to_css(dest)?;
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.border_image_repeat.to_css(dest)
         }
     }
@@ -420,7 +420,7 @@ pub fn parse_border<'i, 't>(
                     self.border_${axis}_start_${prop}.to_css(dest)?;
 
                     if self.border_${axis}_end_${prop} != self.border_${axis}_start_${prop} {
-                        dest.write_str(" ")?;
+                        dest.write_char(' ')?;
                         self.border_${axis}_end_${prop}.to_css(dest)?;
                     }
 
diff --git a/components/style/properties/shorthands/box.mako.rs b/components/style/properties/shorthands/box.mako.rs
index 259febc7507..3d30250b07c 100644
--- a/components/style/properties/shorthands/box.mako.rs
+++ b/components/style/properties/shorthands/box.mako.rs
@@ -203,12 +203,12 @@ ${helpers.two_properties_shorthand(
             self.offset_path.to_css(dest)?;
 
             if !self.offset_distance.is_zero() {
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
                 self.offset_distance.to_css(dest)?;
             }
 
             if !self.offset_rotate.is_auto() {
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
                 self.offset_rotate.to_css(dest)?;
             }
 
diff --git a/components/style/properties/shorthands/font.mako.rs b/components/style/properties/shorthands/font.mako.rs
index 7b87125d065..e1c1c270a5e 100644
--- a/components/style/properties/shorthands/font.mako.rs
+++ b/components/style/properties/shorthands/font.mako.rs
@@ -227,13 +227,13 @@
             % for name in "style variant_caps weight".split():
                 if self.font_${name} != &font_${name}::get_initial_specified_value() {
                     self.font_${name}.to_css(dest)?;
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                 }
             % endfor
 
             if font_stretch != FontStretchKeyword::Normal {
                 font_stretch.to_css(dest)?;
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
             }
 
             self.font_size.to_css(dest)?;
@@ -243,7 +243,7 @@
                 self.line_height.to_css(dest)?;
             }
 
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.font_family.to_css(dest)?;
 
             Ok(())
@@ -443,7 +443,7 @@
             % endif
                     if value != &font_variant_${prop}::get_initial_specified_value() {
                         if has_any {
-                            dest.write_str(" ")?;
+                            dest.write_char(' ')?;
                         }
                         has_any = true;
                         value.to_css(dest)?;
diff --git a/components/style/properties/shorthands/list.mako.rs b/components/style/properties/shorthands/list.mako.rs
index 2d508f22d9e..10a43f83f4c 100644
--- a/components/style/properties/shorthands/list.mako.rs
+++ b/components/style/properties/shorthands/list.mako.rs
@@ -120,7 +120,7 @@
             }
             if self.list_style_image != &ListStyleImage::None {
                 if have_one_non_initial_value {
-                    dest.write_str(" ")?;
+                   dest.write_char(' ')?;
                 }
                 self.list_style_image.to_css(dest)?;
                 have_one_non_initial_value = true;
@@ -131,7 +131,7 @@
             let type_is_initial = self.list_style_type == &ListStyleType::Disc;
             if !type_is_initial {
                 if have_one_non_initial_value {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                 }
                 self.list_style_type.to_css(dest)?;
                 have_one_non_initial_value = true;
diff --git a/components/style/properties/shorthands/position.mako.rs b/components/style/properties/shorthands/position.mako.rs
index b5899593bfd..471e67c0986 100644
--- a/components/style/properties/shorthands/position.mako.rs
+++ b/components/style/properties/shorthands/position.mako.rs
@@ -138,7 +138,7 @@
             self.row_gap.to_css(dest)
           } else {
             self.row_gap.to_css(dest)?;
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.column_gap.to_css(dest)
           }
       }
@@ -497,7 +497,7 @@
                                                                   .zip(&mut names_iter)
                                                                   .zip(track_list.values.iter()) {
                     if i > 0 {
-                        dest.write_str(" ")?;
+                        dest.write_char(' ')?;
                     }
 
                     if !names.is_empty() {
@@ -508,7 +508,7 @@
 
                     // If the track size is the initial value then it's redundant here.
                     if !value.is_initial() {
-                        dest.write_str(" ")?;
+                        dest.write_char(' ')?;
                         value.to_css(dest)?;
                     }
                 }
@@ -665,7 +665,7 @@
                 }
 
                 if !self.grid_auto_columns.is_initial() {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                     self.grid_auto_columns.to_css(dest)?;
                 }
 
@@ -691,7 +691,7 @@
             }
 
             if !self.grid_auto_rows.is_initial() {
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
                 self.grid_auto_rows.to_css(dest)?;
             }
 
@@ -749,7 +749,7 @@
         fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result where W: fmt::Write {
             self.align_content.to_css(dest)?;
             if self.align_content.0 != self.justify_content.0 {
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
                 self.justify_content.to_css(dest)?;
             }
             Ok(())
@@ -790,7 +790,7 @@
         fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result where W: fmt::Write {
             self.align_self.to_css(dest)?;
             if self.align_self.0 != self.justify_self.0 {
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
                 self.justify_self.to_css(dest)?;
             }
             Ok(())
@@ -832,7 +832,7 @@
         fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result where W: fmt::Write {
             self.align_items.to_css(dest)?;
             if self.align_items.0 != self.justify_items.0 {
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
                 self.justify_items.to_css(dest)?;
             }
 
diff --git a/components/style/properties/shorthands/svg.mako.rs b/components/style/properties/shorthands/svg.mako.rs
index 99461a51487..97cce9ad04d 100644
--- a/components/style/properties/shorthands/svg.mako.rs
+++ b/components/style/properties/shorthands/svg.mako.rs
@@ -150,7 +150,7 @@
                 image.to_css(dest)?;
 
                 if *mode != mask_mode::single_value::get_initial_specified_value() {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                     mode.to_css(dest)?;
                 }
 
@@ -158,7 +158,7 @@
                     *position_y != PositionComponent::zero() ||
                     *size != mask_size::single_value::get_initial_specified_value()
                 {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                     Position {
                         horizontal: position_x.clone(),
                         vertical: position_y.clone()
@@ -171,21 +171,21 @@
                 }
 
                 if *repeat != mask_repeat::single_value::get_initial_specified_value() {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                     repeat.to_css(dest)?;
                 }
 
                 if *origin != Origin::BorderBox || *clip != Clip::BorderBox {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                     origin.to_css(dest)?;
                     if *clip != From::from(*origin) {
-                        dest.write_str(" ")?;
+                        dest.write_char(' ')?;
                         clip.to_css(dest)?;
                     }
                 }
 
                 if *composite != mask_composite::single_value::get_initial_specified_value() {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                     composite.to_css(dest)?;
                 }
             }
diff --git a/components/style/properties/shorthands/text.mako.rs b/components/style/properties/shorthands/text.mako.rs
index 074de01aef2..34d3cd5c5db 100644
--- a/components/style/properties/shorthands/text.mako.rs
+++ b/components/style/properties/shorthands/text.mako.rs
@@ -91,7 +91,7 @@
             % if engine == "gecko":
             if !is_auto_thickness {
                 if has_value {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                 }
                 self.text_decoration_thickness.to_css(dest)?;
                 has_value = true;
@@ -99,7 +99,7 @@
 
             if !is_solid_style {
                 if has_value {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                 }
                 self.text_decoration_style.to_css(dest)?;
                 has_value = true;
@@ -107,7 +107,7 @@
 
             if !is_current_color {
                 if has_value {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                 }
                 self.text_decoration_color.to_css(dest)?;
                 has_value = true;
diff --git a/components/style/properties/shorthands/ui.mako.rs b/components/style/properties/shorthands/ui.mako.rs
index 4b99243b59c..b869db9c968 100644
--- a/components/style/properties/shorthands/ui.mako.rs
+++ b/components/style/properties/shorthands/ui.mako.rs
@@ -154,7 +154,7 @@ macro_rules! try_parse_one {
                     self.transition_property.0[i].to_css(dest)?;
                 }
                 % for name in "duration timing_function delay".split():
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                     self.transition_${name}.0[i].to_css(dest)?;
                 % endfor
             }
@@ -289,7 +289,7 @@ macro_rules! try_parse_one {
 
                 % for name in props[2:]:
                     self.animation_${name}.0[i].to_css(dest)?;
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                 % endfor
 
                 self.animation_name.0[i].to_css(dest)?;
diff --git a/components/style/queries/feature_expression.rs b/components/style/queries/feature_expression.rs
index b4715c00739..ec0e7f5b113 100644
--- a/components/style/queries/feature_expression.rs
+++ b/components/style/queries/feature_expression.rs
@@ -263,7 +263,7 @@ impl ToCss for QueryFeatureExpression {
     where
         W: fmt::Write,
     {
-        dest.write_str("(")?;
+        dest.write_char('(')?;
 
         match self.kind {
             QueryFeatureExpressionKind::Empty => self.write_name(dest)?,
diff --git a/components/style/selector_parser.rs b/components/style/selector_parser.rs
index c401fe431ce..baf9ce83e61 100644
--- a/components/style/selector_parser.rs
+++ b/components/style/selector_parser.rs
@@ -129,7 +129,7 @@ where
     T: Debug,
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.write_str("[")?;
+        f.write_char('[')?;
         let mut first = true;
         for entry in self.entries.iter() {
             if !first {
@@ -138,7 +138,7 @@ where
             first = false;
             entry.fmt(f)?;
         }
-        f.write_str("]")
+        f.write_char(']')
     }
 }
 
diff --git a/components/style/servo/selector_parser.rs b/components/style/servo/selector_parser.rs
index 901ef71071e..08431dba684 100644
--- a/components/style/servo/selector_parser.rs
+++ b/components/style/servo/selector_parser.rs
@@ -337,7 +337,7 @@ impl ToCss for NonTSPseudoClass {
         if let Lang(ref lang) = *self {
             dest.write_str(":lang(")?;
             serialize_identifier(lang, dest)?;
-            return dest.write_str(")");
+            return dest.write_char(')');
         }
 
         dest.write_str(match *self {
diff --git a/components/style/servo/url.rs b/components/style/servo/url.rs
index f4ae4e25edf..2186be7aabd 100644
--- a/components/style/servo/url.rs
+++ b/components/style/servo/url.rs
@@ -158,7 +158,7 @@ impl ToCss for CssUrl {
 
         dest.write_str("url(")?;
         string.to_css(dest)?;
-        dest.write_str(")")
+        dest.write_char(')')
     }
 }
 
@@ -230,7 +230,7 @@ impl ToCss for ComputedUrl {
 
         dest.write_str("url(")?;
         string.to_css(dest)?;
-        dest.write_str(")")
+        dest.write_char(')')
     }
 }
 
diff --git a/components/style/stylesheets/document_rule.rs b/components/style/stylesheets/document_rule.rs
index c4e70855801..baf2dd21e71 100644
--- a/components/style/stylesheets/document_rule.rs
+++ b/components/style/stylesheets/document_rule.rs
@@ -47,7 +47,7 @@ impl ToCssWithGuard for DocumentRule {
         self.condition.to_css(&mut CssWriter::new(dest))?;
         dest.write_str(" {")?;
         for rule in self.rules.read_with(guard).0.iter() {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             rule.to_css(guard, dest)?;
         }
         dest.write_str(" }")
diff --git a/components/style/stylesheets/font_feature_values_rule.rs b/components/style/stylesheets/font_feature_values_rule.rs
index 784628f0dde..33b57e5fcfd 100644
--- a/components/style/stylesheets/font_feature_values_rule.rs
+++ b/components/style/stylesheets/font_feature_values_rule.rs
@@ -46,7 +46,7 @@ impl<T: ToCss> ToCss for FFVDeclaration<T> {
         serialize_atom_identifier(&self.name, dest)?;
         dest.write_str(": ")?;
         self.value.to_css(dest)?;
-        dest.write_str(";")
+        dest.write_char(';')
     }
 }
 
@@ -335,7 +335,7 @@ macro_rules! font_feature_values_blocks {
                 self.family_names.to_css(&mut CssWriter::new(dest))?;
                 dest.write_str(" {\n")?;
                 self.value_to_css(&mut CssWriter::new(dest))?;
-                dest.write_str("}")
+                dest.write_char('}')
             }
         }
 
diff --git a/components/style/stylesheets/font_palette_values_rule.rs b/components/style/stylesheets/font_palette_values_rule.rs
index 3bfae5e6b1b..b6085b7884d 100644
--- a/components/style/stylesheets/font_palette_values_rule.rs
+++ b/components/style/stylesheets/font_palette_values_rule.rs
@@ -61,7 +61,7 @@ impl ToCss for FontPaletteOverrideColor {
         W: fmt::Write,
     {
         self.index.to_css(dest)?;
-        dest.write_str(" ")?;
+        dest.write_char(' ')?;
         self.color.to_css(dest)
     }
 }
@@ -200,7 +200,7 @@ impl ToCssWithGuard for FontPaletteValuesRule {
         self.name.to_css(&mut CssWriter::new(dest))?;
         dest.write_str(" { ")?;
         self.value_to_css(&mut CssWriter::new(dest))?;
-        dest.write_str("}")
+        dest.write_char('}')
     }
 }
 
diff --git a/components/style/stylesheets/style_rule.rs b/components/style/stylesheets/style_rule.rs
index 905e067f730..1d4a2e27316 100644
--- a/components/style/stylesheets/style_rule.rs
+++ b/components/style/stylesheets/style_rule.rs
@@ -71,9 +71,9 @@ impl ToCssWithGuard for StyleRule {
         declaration_block.to_css(dest)?;
         // Step 4
         if !declaration_block.declarations().is_empty() {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
         }
         // Step 5
-        dest.write_str("}")
+        dest.write_char('}')
     }
 }
diff --git a/components/style/stylesheets/supports_rule.rs b/components/style/stylesheets/supports_rule.rs
index b0bda2a6169..763e1f891a1 100644
--- a/components/style/stylesheets/supports_rule.rs
+++ b/components/style/stylesheets/supports_rule.rs
@@ -296,9 +296,9 @@ impl ToCss for SupportsCondition {
                 cond.to_css(dest)
             },
             SupportsCondition::Parenthesized(ref cond) => {
-                dest.write_str("(")?;
+                dest.write_char('(')?;
                 cond.to_css(dest)?;
-                dest.write_str(")")
+                dest.write_char(')')
             },
             SupportsCondition::And(ref vec) => {
                 let mut first = true;
@@ -323,31 +323,31 @@ impl ToCss for SupportsCondition {
                 Ok(())
             },
             SupportsCondition::Declaration(ref decl) => {
-                dest.write_str("(")?;
+                dest.write_char('(')?;
                 decl.to_css(dest)?;
-                dest.write_str(")")
+                dest.write_char(')')
             },
             SupportsCondition::Selector(ref selector) => {
                 dest.write_str("selector(")?;
                 selector.to_css(dest)?;
-                dest.write_str(")")
+                dest.write_char(')')
             },
             SupportsCondition::MozBoolPref(ref name) => {
                 dest.write_str("-moz-bool-pref(")?;
                 let name =
                     str::from_utf8(name.as_bytes()).expect("Should be parsed from valid UTF-8");
                 name.to_css(dest)?;
-                dest.write_str(")")
+                dest.write_char(')')
             },
             SupportsCondition::FontFormat(ref kw) => {
                 dest.write_str("font-format(")?;
                 kw.to_css(dest)?;
-                dest.write_str(")")
+                dest.write_char(')')
             },
             SupportsCondition::FontTech(ref flag) => {
                 dest.write_str("font-tech(")?;
                 flag.to_css(dest)?;
-                dest.write_str(")")
+                dest.write_char(')')
             },
             SupportsCondition::FutureSyntax(ref s) => dest.write_str(&s),
         }
diff --git a/components/style/stylesheets/viewport_rule.rs b/components/style/stylesheets/viewport_rule.rs
index 42a29a4b6ec..73e16201638 100644
--- a/components/style/stylesheets/viewport_rule.rs
+++ b/components/style/stylesheets/viewport_rule.rs
@@ -108,7 +108,7 @@ macro_rules! declare_viewport_descriptor_inner {
                         },
                     )*
                 }
-                dest.write_str(";")
+                dest.write_char(';')
             }
         }
     };
@@ -504,7 +504,7 @@ impl ToCssWithGuard for ViewportRule {
         let mut iter = self.declarations.iter();
         iter.next().unwrap().to_css(&mut CssWriter::new(dest))?;
         for declaration in iter {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             declaration.to_css(&mut CssWriter::new(dest))?;
         }
         dest.write_str(" }")
diff --git a/components/style/values/computed/image.rs b/components/style/values/computed/image.rs
index 5f650631c89..fc484979153 100644
--- a/components/style/values/computed/image.rs
+++ b/components/style/values/computed/image.rs
@@ -177,7 +177,7 @@ impl generic::LineDirection for LineDirection {
                     dest.write_str("to ")?;
                 }
                 x.to_css(dest)?;
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
                 y.to_css(dest)
             },
         }
diff --git a/components/style/values/computed/position.rs b/components/style/values/computed/position.rs
index 6d09e327e63..5a10c0f23d7 100644
--- a/components/style/values/computed/position.rs
+++ b/components/style/values/computed/position.rs
@@ -53,7 +53,7 @@ impl ToCss for Position {
         W: Write,
     {
         self.horizontal.to_css(dest)?;
-        dest.write_str(" ")?;
+        dest.write_char(' ')?;
         self.vertical.to_css(dest)
     }
 }
diff --git a/components/style/values/computed/text.rs b/components/style/values/computed/text.rs
index c2b017f3973..ff4d87fa93e 100644
--- a/components/style/values/computed/text.rs
+++ b/components/style/values/computed/text.rs
@@ -161,7 +161,7 @@ impl ToCss for TextOverflow {
             self.second.to_css(dest)?;
         } else {
             self.first.to_css(dest)?;
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.second.to_css(dest)?;
         }
         Ok(())
diff --git a/components/style/values/computed/time.rs b/components/style/values/computed/time.rs
index 1f0a6df018b..f542333a823 100644
--- a/components/style/values/computed/time.rs
+++ b/components/style/values/computed/time.rs
@@ -40,6 +40,6 @@ impl ToCss for Time {
         W: Write,
     {
         self.seconds().to_css(dest)?;
-        dest.write_str("s")
+        dest.write_char('s')
     }
 }
diff --git a/components/style/values/generics/basic_shape.rs b/components/style/values/generics/basic_shape.rs
index 5e1bafb2230..870b6c82b5b 100644
--- a/components/style/values/generics/basic_shape.rs
+++ b/components/style/values/generics/basic_shape.rs
@@ -418,7 +418,7 @@ where
             dest.write_str(" round ")?;
             self.round.to_css(dest)?;
         }
-        dest.write_str(")")
+        dest.write_char(')')
     }
 }
 
@@ -434,11 +434,11 @@ where
         dest.write_str("circle(")?;
         if self.radius != Default::default() {
             self.radius.to_css(dest)?;
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
         }
         dest.write_str("at ")?;
         self.position.to_css(dest)?;
-        dest.write_str(")")
+        dest.write_char(')')
     }
 }
 
@@ -454,13 +454,13 @@ where
         dest.write_str("ellipse(")?;
         if self.semiaxis_x != Default::default() || self.semiaxis_y != Default::default() {
             self.semiaxis_x.to_css(dest)?;
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.semiaxis_y.to_css(dest)?;
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
         }
         dest.write_str("at ")?;
         self.position.to_css(dest)?;
-        dest.write_str(")")
+        dest.write_char(')')
     }
 }
 
diff --git a/components/style/values/generics/calc.rs b/components/style/values/generics/calc.rs
index 24b0cf23a32..9175a0debf6 100644
--- a/components/style/values/generics/calc.rs
+++ b/components/style/values/generics/calc.rs
@@ -1078,7 +1078,7 @@ impl<L: CalcNodeLeaf> CalcNode<L> {
         }
 
         if write_closing_paren {
-            dest.write_str(")")?;
+            dest.write_char(')')?;
         }
         Ok(())
     }
diff --git a/components/style/values/generics/color.rs b/components/style/values/generics/color.rs
index 6c82cbf2aed..439be95ca44 100644
--- a/components/style/values/generics/color.rs
+++ b/components/style/values/generics/color.rs
@@ -230,16 +230,16 @@ impl<Color: ToCss, Percentage: ToCss + ToPercentage> ToCss for ColorMix<Color, P
         dest.write_str(", ")?;
         self.left.to_css(dest)?;
         if !can_omit(&self.left_percentage, &self.right_percentage, true) {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.left_percentage.to_css(dest)?;
         }
         dest.write_str(", ")?;
         self.right.to_css(dest)?;
         if !can_omit(&self.right_percentage, &self.left_percentage, false) {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.right_percentage.to_css(dest)?;
         }
-        dest.write_str(")")
+        dest.write_char(')')
     }
 }
 
diff --git a/components/style/values/generics/counters.rs b/components/style/values/generics/counters.rs
index c83a336f948..eeb97baef4b 100644
--- a/components/style/values/generics/counters.rs
+++ b/components/style/values/generics/counters.rs
@@ -50,12 +50,12 @@ where
         }
         self.name.to_css(dest)?;
         if self.is_reversed {
-            dest.write_str(")")?;
+            dest.write_char(')')?;
             if self.value == i32::min_value() {
                 return Ok(());
             }
         }
-        dest.write_str(" ")?;
+        dest.write_char(' ')?;
         self.value.to_css(dest)
     }
 }
diff --git a/components/style/values/generics/grid.rs b/components/style/values/generics/grid.rs
index 46b1a65ba34..4d0faa3ac3b 100644
--- a/components/style/values/generics/grid.rs
+++ b/components/style/values/generics/grid.rs
@@ -109,14 +109,14 @@ where
 
         if !self.line_num.is_zero() {
             if self.is_span {
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
             }
             self.line_num.to_css(dest)?;
         }
 
         if self.ident != atom!("") {
             if self.is_span || !self.line_num.is_zero() {
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
             }
             CustomIdent(self.ident.clone()).to_css(dest)?;
         }
@@ -341,12 +341,12 @@ impl<L: ToCss> ToCss for TrackSize<L> {
                 min.to_css(dest)?;
                 dest.write_str(", ")?;
                 max.to_css(dest)?;
-                dest.write_str(")")
+                dest.write_char(')')
             },
             TrackSize::FitContent(ref lp) => {
                 dest.write_str("fit-content(")?;
                 lp.to_css(dest)?;
-                dest.write_str(")")
+                dest.write_char(')')
             },
         }
     }
@@ -493,7 +493,7 @@ impl<L: ToCss, I: ToCss> ToCss for TrackRepeat<L, I> {
             .enumerate()
         {
             if i > 0 {
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
             }
 
             concat_serialize_idents("[", "] ", names, " ", dest)?;
@@ -504,7 +504,7 @@ impl<L: ToCss, I: ToCss> ToCss for TrackRepeat<L, I> {
             concat_serialize_idents(" [", "]", line_names_last, " ", dest)?;
         }
 
-        dest.write_str(")")?;
+        dest.write_char(')')?;
 
         Ok(())
     }
@@ -615,7 +615,7 @@ impl<L: ToCss, I: ToCss> ToCss for TrackList<L, I> {
             match values_iter.next() {
                 Some(value) => {
                     if !names.is_empty() {
-                        dest.write_str(" ")?;
+                        dest.write_char(' ')?;
                     }
 
                     value.to_css(dest)?;
@@ -627,7 +627,7 @@ impl<L: ToCss, I: ToCss> ToCss for TrackList<L, I> {
                 line_names_iter.peek().map_or(false, |v| !v.is_empty()) ||
                 (idx + 1 == self.auto_repeat_index)
             {
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
             }
         }
 
@@ -753,14 +753,14 @@ impl ToCss for LineNameList {
             if let Some((ref first, rest)) = names.split_first() {
                 first.to_css(dest)?;
                 for name in rest {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                     name.to_css(dest)?;
                 }
             }
 
-            dest.write_str("]")?;
+            dest.write_char(']')?;
             if fill_len > 0 && i == fill_start + fill_len - 1 {
-                dest.write_str(")")?;
+                dest.write_char(')')?;
             }
         }
 
diff --git a/components/style/values/generics/image.rs b/components/style/values/generics/image.rs
index d5e830810a8..3b84d982381 100644
--- a/components/style/values/generics/image.rs
+++ b/components/style/values/generics/image.rs
@@ -142,14 +142,14 @@ impl<I: style_traits::ToCss, R: style_traits::ToCss> ToCss for GenericImageSetIt
         W: fmt::Write,
     {
         self.image.to_css(dest)?;
-        dest.write_str(" ")?;
+        dest.write_char(' ')?;
         self.resolution.to_css(dest)?;
 
         if self.has_mime_type {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             dest.write_str("type(")?;
             self.mime_type.to_css(dest)?;
-            dest.write_str(")")?;
+            dest.write_char(')')?;
         }
         Ok(())
     }
@@ -369,7 +369,7 @@ impl ToCss for PaintWorklet {
             dest.write_str(", ")?;
             argument.to_css(dest)?;
         }
-        dest.write_str(")")
+        dest.write_char(')')
     }
 }
 
@@ -433,7 +433,7 @@ where
             Image::Element(ref selector) => {
                 dest.write_str("-moz-element(#")?;
                 serialize_atom_identifier(selector, dest)?;
-                dest.write_str(")")
+                dest.write_char(')')
             },
             Image::ImageSet(ref is) => is.to_css(dest),
             Image::CrossFade(ref cf) => cf.to_css(dest),
@@ -520,7 +520,7 @@ where
                     if !omit_shape {
                         shape.to_css(dest)?;
                         if !omit_position {
-                            dest.write_str(" ")?;
+                            dest.write_char(' ')?;
                         }
                     }
                     if !omit_position {
@@ -560,7 +560,7 @@ where
                     dest.write_str("from ")?;
                     angle.to_css(dest)?;
                     if !omit_position {
-                        dest.write_str(" ")?;
+                        dest.write_char(' ')?;
                     }
                 }
                 if !omit_position {
@@ -577,7 +577,7 @@ where
                 }
             },
         }
-        dest.write_str(")")
+        dest.write_char(')')
     }
 }
 
diff --git a/components/style/values/generics/rect.rs b/components/style/values/generics/rect.rs
index dee21459a77..e6358373d66 100644
--- a/components/style/values/generics/rect.rs
+++ b/components/style/values/generics/rect.rs
@@ -110,17 +110,17 @@ where
         if same_vertical && same_horizontal && self.0 == self.1 {
             return Ok(());
         }
-        dest.write_str(" ")?;
+        dest.write_char(' ')?;
         self.1.to_css(dest)?;
         if same_vertical && same_horizontal {
             return Ok(());
         }
-        dest.write_str(" ")?;
+        dest.write_char(' ')?;
         self.2.to_css(dest)?;
         if same_horizontal {
             return Ok(());
         }
-        dest.write_str(" ")?;
+        dest.write_char(' ')?;
         self.3.to_css(dest)
     }
 }
diff --git a/components/style/values/generics/size.rs b/components/style/values/generics/size.rs
index e00eef28b93..0027245e488 100644
--- a/components/style/values/generics/size.rs
+++ b/components/style/values/generics/size.rs
@@ -80,7 +80,7 @@ where
         self.width.to_css(dest)?;
 
         if self.height != self.width {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.height.to_css(dest)?;
         }
 
diff --git a/components/style/values/generics/ui.rs b/components/style/values/generics/ui.rs
index 3db04e6586a..1b7dac1da02 100644
--- a/components/style/values/generics/ui.rs
+++ b/components/style/values/generics/ui.rs
@@ -79,9 +79,9 @@ impl<Image: ToCss, Number: ToCss> ToCss for CursorImage<Image, Number> {
     {
         self.image.to_css(dest)?;
         if self.has_hotspot {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.hotspot_x.to_css(dest)?;
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.hotspot_y.to_css(dest)?;
         }
         Ok(())
diff --git a/components/style/values/mod.rs b/components/style/values/mod.rs
index adff582974c..ac43ea62694 100644
--- a/components/style/values/mod.rs
+++ b/components/style/values/mod.rs
@@ -360,7 +360,7 @@ where
     W: Write,
 {
     (value * 100.).to_css(dest)?;
-    dest.write_str("%")
+    dest.write_char('%')
 }
 
 /// Convenience void type to disable some properties and values through types.
diff --git a/components/style/values/specified/angle.rs b/components/style/values/specified/angle.rs
index 08c6b443678..0c8c030a9ca 100644
--- a/components/style/values/specified/angle.rs
+++ b/components/style/values/specified/angle.rs
@@ -97,7 +97,7 @@ impl ToCss for Angle {
         }
         self.value.to_css(dest)?;
         if self.was_calc {
-            dest.write_str(")")?;
+            dest.write_char(')')?;
         }
         Ok(())
     }
diff --git a/components/style/values/specified/background.rs b/components/style/values/specified/background.rs
index 29f6d6b352f..39a5a85193d 100644
--- a/components/style/values/specified/background.rs
+++ b/components/style/values/specified/background.rs
@@ -102,7 +102,7 @@ impl ToCss for BackgroundRepeat {
             (horizontal, vertical) => {
                 horizontal.to_css(dest)?;
                 if horizontal != vertical {
-                    dest.write_str(" ")?;
+                    dest.write_char(' ')?;
                     vertical.to_css(dest)?;
                 }
                 Ok(())
diff --git a/components/style/values/specified/border.rs b/components/style/values/specified/border.rs
index 817a5aadddb..6fe179de71f 100644
--- a/components/style/values/specified/border.rs
+++ b/components/style/values/specified/border.rs
@@ -278,7 +278,7 @@ impl ToCss for BorderImageRepeat {
     {
         self.0.to_css(dest)?;
         if self.0 != self.1 {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.1.to_css(dest)?;
         }
         Ok(())
diff --git a/components/style/values/specified/box.rs b/components/style/values/specified/box.rs
index c72517ffaec..48d778c5904 100644
--- a/components/style/values/specified/box.rs
+++ b/components/style/values/specified/box.rs
@@ -400,11 +400,11 @@ impl ToCss for Display {
                     if self.is_list_item() {
                         if outside != DisplayOutside::Block {
                             outside.to_css(dest)?;
-                            dest.write_str(" ")?;
+                            dest.write_char(' ')?;
                         }
                         if inside != DisplayInside::Flow {
                             inside.to_css(dest)?;
-                            dest.write_str(" ")?;
+                            dest.write_char(' ')?;
                         }
                         dest.write_str("list-item")
                     } else {
@@ -969,7 +969,7 @@ impl ToCss for ScrollSnapType {
         }
         self.axis.to_css(dest)?;
         if self.strictness != ScrollSnapStrictness::Proximity {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.strictness.to_css(dest)?;
         }
         Ok(())
@@ -1054,7 +1054,7 @@ impl ToCss for ScrollSnapAlign {
     {
         self.block.to_css(dest)?;
         if self.block != self.inline {
-            dest.write_str(" ")?;
+            dest.write_char(' ')?;
             self.inline.to_css(dest)?;
         }
         Ok(())
diff --git a/components/style/values/specified/image.rs b/components/style/values/specified/image.rs
index 3eec04893e3..3be84c5a7b2 100644
--- a/components/style/values/specified/image.rs
+++ b/components/style/values/specified/image.rs
@@ -947,7 +947,7 @@ impl generic::LineDirection for LineDirection {
                     dest.write_str("to ")?;
                 }
                 x.to_css(dest)?;
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
                 y.to_css(dest)
             },
         }
diff --git a/components/style/values/specified/mod.rs b/components/style/values/specified/mod.rs
index 3daa61a366b..a566a3fdf89 100644
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@@ -319,7 +319,7 @@ impl ToCss for Number {
         }
         self.value.to_css(dest)?;
         if self.calc_clamping_mode.is_some() {
-            dest.write_str(")")?;
+            dest.write_char(')')?;
         }
         Ok(())
     }
@@ -702,7 +702,7 @@ impl ToCss for Integer {
         }
         self.value.to_css(dest)?;
         if self.was_calc {
-            dest.write_str(")")?;
+            dest.write_char(')')?;
         }
         Ok(())
     }
@@ -950,9 +950,9 @@ impl ToCss for Attr {
         dest.write_str("attr(")?;
         if !self.namespace_prefix.is_empty() {
             serialize_atom_identifier(&self.namespace_prefix, dest)?;
-            dest.write_str("|")?;
+            dest.write_char('|')?;
         }
         serialize_atom_identifier(&self.attribute, dest)?;
-        dest.write_str(")")
+        dest.write_char(')')
     }
 }
diff --git a/components/style/values/specified/percentage.rs b/components/style/values/specified/percentage.rs
index ba5f92db924..62dca187635 100644
--- a/components/style/values/specified/percentage.rs
+++ b/components/style/values/specified/percentage.rs
@@ -40,7 +40,7 @@ impl ToCss for Percentage {
         serialize_percentage(self.value, dest)?;
 
         if self.calc_clamping_mode.is_some() {
-            dest.write_str(")")?;
+            dest.write_char(')')?;
         }
         Ok(())
     }
diff --git a/components/style/values/specified/position.rs b/components/style/values/specified/position.rs
index e447c52f0c4..06456a312fc 100644
--- a/components/style/values/specified/position.rs
+++ b/components/style/values/specified/position.rs
@@ -224,12 +224,12 @@ impl ToCss for Position {
             ) => {
                 dest.write_str("left ")?;
                 x_lp.to_css(dest)?;
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
                 y_pos.to_css(dest)
             },
             (x_pos, y_pos) => {
                 x_pos.to_css(dest)?;
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
                 y_pos.to_css(dest)
             },
         }
diff --git a/components/style/values/specified/svg.rs b/components/style/values/specified/svg.rs
index f06fc43c46d..73e0b16ac5c 100644
--- a/components/style/values/specified/svg.rs
+++ b/components/style/values/specified/svg.rs
@@ -239,7 +239,7 @@ impl ToCss for SVGPaintOrder {
 
         for pos in 0..last_pos_to_serialize + 1 {
             if pos != 0 {
-                dest.write_str(" ")?
+                dest.write_char(' ')?
             }
             self.order_at(pos).to_css(dest)?;
         }
diff --git a/components/style/values/specified/text.rs b/components/style/values/specified/text.rs
index b782780c955..8545a4fc01a 100644
--- a/components/style/values/specified/text.rs
+++ b/components/style/values/specified/text.rs
@@ -373,7 +373,7 @@ impl ToCss for TextTransform {
         if self.case_ != TextTransformCase::None {
             self.case_.to_css(dest)?;
             if !self.other_.is_empty() {
-                dest.write_str(" ")?;
+                dest.write_char(' ')?;
             }
         }
 
diff --git a/components/style/values/specified/time.rs b/components/style/values/specified/time.rs
index aba3f0a828f..bac9efd413c 100644
--- a/components/style/values/specified/time.rs
+++ b/components/style/values/specified/time.rs
@@ -159,7 +159,7 @@ impl ToCss for Time {
         match self.unit {
             TimeUnit::Second => {
                 self.seconds.to_css(dest)?;
-                dest.write_str("s")?;
+                dest.write_char('s')?;
             },
             TimeUnit::Millisecond => {
                 (self.seconds * 1000.).to_css(dest)?;
@@ -167,7 +167,7 @@ impl ToCss for Time {
             },
         }
         if self.was_calc {
-            dest.write_str(")")?;
+            dest.write_char(')')?;
         }
         Ok(())
     }