diff --git a/.travis.yml b/.travis.yml
index 5ed3b1d..27cdad6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,7 @@
 language: dart
 dart:
 - dev
-- 2.4.0
+- 2.5.0
 # Only building master means that we don't run two builds for each pull request.
 dart_task:
 - test: --platform vm,chrome
diff --git a/lib/src/characters.dart b/lib/src/characters.dart
index 3e5170c..eec3ca8 100644
--- a/lib/src/characters.dart
+++ b/lib/src/characters.dart
@@ -178,15 +178,20 @@
 
   /// Replaces [pattern] with [replacement].
   ///
-  /// Returns a new [GrapehemeClusters] where all occurrences of the
-  /// [pattern] character sequence are replaced by [replacement],
-  /// unless the occurrence overlaps a prior replaced sequence.
+  /// Returns a new [Characters] sequence where all occurrences of the
+  /// [pattern] characters are replaced by [replacement],
+  /// unless the occurrence overlaps a prior
+  /// replaced occurrence of [pattern].
+  ///
+  /// Returns the current characters if there is no occurrence of [pattern].
   Characters replaceAll(Characters pattern, Characters replacement);
 
-  /// Replaces the first [pattern] with [replacement].
+  /// Replaces the first occurrence of [pattern] with [replacement].
   ///
   /// Returns a new [Characters] where the first occurence of the
   /// [pattern] character sequence, if any, is replaced by [replacement].
+  ///
+  /// Returns the current characters if there is no occurrence of [pattern].
   Characters replaceFirst(Characters pattern, Characters replacement);
 
   /// The characters of the lower-case version of [string].
@@ -250,7 +255,22 @@
   /// The code points of the current character range.
   Runes get runes;
 
-  /// Creates a copy of this [Character].
+  /// The characters of this range.
+  Characters get currentCharacters;
+
+  /// The characters before the current range.
+  Characters get charactersBefore;
+
+  /// The characters after the current range.
+  Characters get charactersAfter;
+
+  /// The string of the characters before the current range.
+  String get stringBefore;
+
+  /// The string of the characters after the current range.
+  String get stringAfter;
+
+  /// Creates a copy of this [CharacterRange].
   ///
   /// The copy is in the exact same state as this iterator.
   /// Can be used to iterate the following characters more than once
@@ -283,6 +303,9 @@
   /// and `false` if not.
   bool moveNext([int count = 1]);
 
+  /// Moves the range to be everything after the current range.
+  void moveNextAll();
+
   /// Moves the range to the next occurrence of [target]
   /// after the current range.
   ///
@@ -325,6 +348,9 @@
   /// and `false` if not.
   bool moveBack([int count = 1]);
 
+  /// Moves the range to be everything before the current range.
+  void moveBackAll();
+
   /// Moves the range to the last occurrence of [target]
   /// before the current range.
   ///
@@ -587,33 +613,58 @@
   /// which gives the same effect as [collapseToStart].
   void dropBackWhile(bool Function(String) test);
 
-  /// Creates a new [Characters] sequence by replacing the current range.
+  /// Replaces the current range with [replacement] and returns the result.
   ///
-  /// Replaces the current range in [source] with [replacement].
+  /// Replaces the current range in [source] with [replacement]
+  /// and returns a range of the resulting characters
+  /// which contains the replacement characters.
   ///
-  /// Returns a new [Characters] instance. Since the inserted characters
-  /// may combine with the preceding or following characters, grapheme cluster
-  /// boundaries need to be recomputed from scratch.
-  Characters replaceRange(Characters replacement);
+  /// The inserted characters may combine with
+  /// the preceding or following code points,
+  /// so that the start and end of the original range
+  /// are no longer grapheme cluster boundaries.
+  /// In that case, the returned range may extend into into the code points
+  /// before and after the original range.
+  CharacterRange replaceRange(Characters replacement);
 
-  /// Replaces all occurrences of [pattern] in the range with [replacement].
+  /// Replaces [pattern] in the current range with [replacement].
   ///
-  /// Replaces the first occurrence of [pattern] in the range, then repeatedly
-  /// finds and replaces the next occurrence which does not overlap with
-  /// the earlier, already replaced, occurrence.
+  /// Replaces all occurrences of [pattern] in the current range with
+  /// [replacement], unless they overlap with an earlier occurrence of
+  /// [pattern] which was replaced.
+  /// Then returns a range on the resulting characters
+  /// which contains all inserted replacement characters
+  /// and any remaining characters of the original range.
   ///
-  /// Returns new [Characters] instance for the resulting string.
-  Characters replaceAll(Characters pattern, Characters replacement);
+  /// The inserted characters may combine with
+  /// the preceding or following code points,
+  /// so that the start and end of the original range
+  /// are no longer grapheme cluster boundaries.
+  /// In that case, the returned range may extend into into the code points
+  /// before and after the original range.
+  ///
+  /// Returns `null` if there are no occurrences of [pattern]
+  /// in the current range.
+  CharacterRange /*?*/ replaceAll(Characters pattern, Characters replacement);
 
   /// Replaces the first occurrence of [pattern] with [replacement].
   ///
   /// Finds the first occurrence of [pattern] in the current range,
-  /// then replaces that occurrence with [replacement] and returns
-  /// the [Characters] of that string.
+  /// then replaces that occurrence with [replacement].
+  /// Then returns a range on the resulting characters
+  /// which contains the inserted replacement characters
+  /// and any remaining characters of the original range.
   ///
-  /// If there is no first occurrence of [pattern], then the
-  /// characters of the source string is returned.
-  Characters replaceFirst(Characters pattern, Characters replacement);
+  /// The inserted characters may combine with
+  /// the preceding or following code points,
+  /// so that the start and end of the original range
+  /// are no longer grapheme cluster boundaries.
+  /// In that case, the returned range may extend into into the code points
+  /// before and after the original range.
+  ///
+  /// Returns `null` if there are no occurrences of [pattern]
+  /// in the current range.
+  CharacterRange /*?*/ replaceFirst(Characters pattern, Characters replacement);
 
   /// Whether the current range starts with [characters].
   ///
diff --git a/lib/src/characters_impl.dart b/lib/src/characters_impl.dart
index 109d750..46b10b6 100644
--- a/lib/src/characters_impl.dart
+++ b/lib/src/characters_impl.dart
@@ -148,14 +148,11 @@
 
   @override
   Characters replaceAll(Characters pattern, Characters replacement) =>
-      _rangeAll.replaceAll(pattern, replacement);
+      _rangeAll.replaceAll(pattern, replacement)?.source ?? this;
 
   @override
-  Characters replaceFirst(Characters pattern, Characters replacement) {
-    var range = _rangeAll;
-    if (!range.collapseToFirst(pattern)) return this;
-    return range.replaceRange(replacement);
-  }
+  Characters replaceFirst(Characters pattern, Characters replacement) =>
+      _rangeAll.replaceFirst(pattern, replacement)?.source ?? this;
 
   @override
   bool containsAll(Characters other) =>
@@ -750,32 +747,37 @@
   }
 
   @override
-  Characters replaceFirst(Characters pattern, Characters replacement) {
+  CharacterRange /*?*/ replaceFirst(
+      Characters pattern, Characters replacement) {
     String patternString = pattern.string;
     String replacementString = replacement.string;
+    String replaced;
     if (patternString.isEmpty) {
-      return StringCharacters(
-          _string.replaceRange(_start, _start, replacementString));
+      replaced = _string.replaceRange(_start, _start, replacementString);
+    } else {
+      int index = _indexOf(_string, patternString, _start, _end);
+      if (index >= 0) {
+        replaced = _string.replaceRange(
+            index, index + patternString.length, replacementString);
+      } else {
+        return null;
+      }
     }
-    int index = _indexOf(_string, patternString, _start, _end);
-    String result = _string;
-    if (index >= 0) {
-      result = _string.replaceRange(
-          index, index + patternString.length, replacementString);
-    }
-    return StringCharacters(result);
+    int newEnd = replaced.length - _string.length + _end;
+    return _expandRange(replaced, _start, newEnd);
   }
 
   @override
-  Characters replaceAll(Characters pattern, Characters replacement) {
+  CharacterRange /*?*/ replaceAll(Characters pattern, Characters replacement) {
     var patternString = pattern.string;
     var replacementString = replacement.string;
     if (patternString.isEmpty) {
       var replaced = _explodeReplace(
           _string, _start, _end, replacementString, replacementString);
-      return StringCharacters(replaced);
+      int newEnd = replaced.length - (_string.length - _end);
+      return _expandRange(replaced, _start, newEnd);
     }
-    if (_start == _end) return Characters(_string);
+    if (_start == _end) return null;
     int start = 0;
     int cursor = _start;
     StringBuffer buffer;
@@ -786,14 +788,26 @@
       cursor += patternString.length;
       start = cursor;
     }
-    if (buffer == null) return Characters(_string);
+    if (buffer == null) return null;
     buffer.write(_string.substring(start));
-    return Characters(buffer.toString());
+    String replaced = buffer.toString();
+    int newEnd = replaced.length - (_string.length - _end);
+    return _expandRange(replaced, _start, newEnd);
   }
 
   @override
-  Characters replaceRange(Characters replacement) {
-    return Characters(_string.replaceRange(_start, _end, replacement.string));
+  CharacterRange replaceRange(Characters replacement) {
+    String replacementString = replacement.string;
+    String resultString = _string.replaceRange(_start, _end, replacementString);
+    return _expandRange(
+        resultString, _start, _start + replacementString.length);
+  }
+
+  // Expands a range if its start or end are not grapheme cluster boundaries.
+  StringCharacterRange _expandRange(String string, int start, int end) {
+    start = previousBreak(string, 0, string.length, start);
+    end = nextBreak(string, 0, string.length, end);
+    return StringCharacterRange._(string, start, end);
   }
 
   @override
@@ -856,6 +870,32 @@
     }
     return false;
   }
+
+  @override
+  Characters get charactersAfter => StringCharacters(_string.substring(_end));
+
+  @override
+  Characters get charactersBefore =>
+      StringCharacters(_string.substring(0, _start));
+
+  @override
+  Characters get currentCharacters => StringCharacters(current);
+
+  @override
+  void moveBackAll() {
+    _move(0, _start);
+  }
+
+  @override
+  void moveNextAll() {
+    _move(_end, _string.length);
+  }
+
+  @override
+  String get stringAfter => _string.substring(_end);
+
+  @override
+  String get stringBefore => _string.substring(0, _start);
 }
 
 class _CodeUnits extends ListBase<int> {
diff --git a/lib/src/grapheme_clusters/breaks.dart b/lib/src/grapheme_clusters/breaks.dart
index 9a41609..08d1d84 100644
--- a/lib/src/grapheme_clusters/breaks.dart
+++ b/lib/src/grapheme_clusters/breaks.dart
@@ -295,7 +295,7 @@
   return start != end;
 }
 
-/// The most recent break no later than [position] in
+/// The most recent break no later than [index] in
 /// `string.substring(start, end)`.
 int previousBreak(String text, int start, int end, int index) {
   assert(0 <= start);
@@ -328,7 +328,7 @@
       .nextBreak();
 }
 
-/// The next break no earlier than [position] in `string.substring(start, end)`.
+/// The next break no earlier than [index] in `string.substring(start, end)`.
 ///
 /// The index need not be at a grapheme cluster boundary.
 int nextBreak(String text, int start, int end, int index) {
diff --git a/pubspec.yaml b/pubspec.yaml
index 5f1858c..4084b0b 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: characters
-version: 0.2.0
+version: 0.3.0
 environment:
-  sdk: "^2.4.0"
+  sdk: "^2.5.0"
 dev_dependencies:
   test: "^1.6.0"
diff --git a/test/characters_test.dart b/test/characters_test.dart
index cbb6e03..8ef5ec2 100644
--- a/test/characters_test.dart
+++ b/test/characters_test.dart
@@ -477,7 +477,7 @@
 
     var cs2 = cs.replaceAll(c, gc(""));
     var cs3 = cs.replaceFirst(c, gc(""));
-    var cs4 = cs.findFirst(c).replaceRange(gc(""));
+    var cs4 = cs.findFirst(c).replaceRange(gc("")).source;
     var cse = gc("$a$b$d$e");
     expect(cs2, cse);
     expect(cs3, cse);
@@ -498,9 +498,11 @@
     it.expandTo(b + a);
     expect("$b$a$d$b$a", it.current);
     var cs10 = it.replaceAll(b + a, e + e);
-    expect(cs10, gc("$a$c$e$e$d$e$e"));
+    expect(cs10.currentCharacters, e + e + d + e + e);
+    expect(cs10.source, gc("$a$c$e$e$d$e$e"));
     var cs11 = it.replaceRange(e);
-    expect(cs11, gc("$a$c$e"));
+    expect(cs11.currentCharacters, e);
+    expect(cs11.source, gc("$a$c$e"));
 
     expect(cs.startsWith(gc("")), true);
     expect(cs.startsWith(a), true);
@@ -552,4 +554,66 @@
     expect(it.isFollowedBy(c + d + e), false);
     expect(it.isFollowedBy(e), false);
   });
+  test("replace methods", () {
+    // Unicode grapheme breaking character classes,
+    // represented by their first value.
+
+    var pattern = gc("\t"); // A non-combining entry to be replaced.
+    var non = gc("");
+
+    var c = otr + cr + pattern + lf + pic + pattern + zwj + pic + otr;
+    var r = c.replaceAll(pattern, non);
+    expect(r, otr + cr + lf + pic + zwj + pic + otr);
+    var ci = c.iterator..moveNextAll();
+    var ri = ci.replaceAll(pattern, non);
+    expect(ri.currentCharacters, otr + cr + lf + pic + zwj + pic + otr);
+    ci.dropFirst();
+    ci.dropLast();
+    expect(ci.currentCharacters, cr + pattern + lf + pic + pattern + zwj + pic);
+    expect(ci.currentCharacters.length, 7);
+    ri = ci.replaceAll(pattern, non);
+    expect(ri.currentCharacters, cr + lf + pic + zwj + pic);
+    expect(ri.currentCharacters.length, 2);
+    ci.dropFirst();
+    ci.dropLast(5);
+    expect(ci.currentCharacters, pattern);
+    ri = ci.replaceAll(pattern, non);
+    expect(ri.currentCharacters, cr + lf);
+    ci.moveNext(2);
+    ci.moveNext(1);
+    expect(ci.currentCharacters, pattern);
+    ri = ci.replaceAll(pattern, non);
+    expect(ri.currentCharacters, pic + zwj + pic);
+
+    c = otr + pic + ext + pattern + pic + ext + otr;
+    expect(c.length, 5);
+    ci = c.iterator..moveTo(pattern);
+    expect(ci.currentCharacters, pattern);
+    ri = ci.replaceAll(pattern, zwj);
+    expect(ri.currentCharacters, pic + ext + zwj + pic + ext);
+
+    c = reg + pattern + reg + reg;
+    ci = c.iterator..moveTo(pattern);
+    ri = ci.replaceRange(non);
+    expect(ri.currentCharacters, reg + reg);
+    expect(ri.moveNext(), true);
+    expect(ri.currentCharacters, reg);
+  });
 }
+
+/// Sample characters from each breaking algorithm category.
+final Characters ctl = gc("\x00"); // Control, NUL.
+final Characters cr = gc("\r"); // Carriage Return, CR.
+final Characters lf = gc("\n"); // Newline, NL.
+final Characters otr = gc(" "); // Other, Space.
+final Characters ext = gc("\u0300"); // Extend, Combining Grave Accent.
+final Characters spc = gc("\u0903"); // Spacing Mark, Devanagari Sign Visarga.
+final Characters pre = gc("\u0600"); // Prepend, Arabic Number Sign.
+final Characters zwj = gc("\u200d"); // Zero-Width Joiner.
+final Characters pic = gc("\u00a9"); // Extended Pictographic, Copyright.
+final Characters reg = gc("\u{1f1e6}"); // Regional Identifier "a".
+final Characters hanl = gc("\u1100"); // Hangul L, Choseong Kiyeok.
+final Characters hanv = gc("\u1160"); // Hangul V, Jungseong Filler.
+final Characters hant = gc("\u11a8"); // Hangul T, Jongseong Kiyeok.
+final Characters hanlv = gc("\uac00"); // Hangul LV, Syllable Ga.
+final Characters hanlvt = gc("\uac01"); // Hangul LVT, Syllable Gag.