diff --git a/core/fxcrt/cfx_bytestring.h b/core/fxcrt/cfx_bytestring.h
index 432f28a..b976287 100644
--- a/core/fxcrt/cfx_bytestring.h
+++ b/core/fxcrt/cfx_bytestring.h
@@ -8,6 +8,7 @@
 #define CORE_FXCRT_CFX_BYTESTRING_H_
 
 #include <functional>
+#include <iterator>
 #include <sstream>
 #include <utility>
 
@@ -25,6 +26,7 @@
  public:
   using CharType = char;
   using const_iterator = const CharType*;
+  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
   CFX_ByteString();
   CFX_ByteString(const CFX_ByteString& other);
@@ -77,6 +79,14 @@
     return m_pData ? m_pData->m_String + m_pData->m_nDataLength : nullptr;
   }
 
+  // Note: Any subsequent modification of |this| will invalidate iterators.
+  const_reverse_iterator rbegin() const {
+    return const_reverse_iterator(end());
+  }
+  const_reverse_iterator rend() const {
+    return const_reverse_iterator(begin());
+  }
+
   FX_STRSIZE GetLength() const { return m_pData ? m_pData->m_nDataLength : 0; }
   FX_STRSIZE GetStringLength() const {
     return m_pData ? FXSYS_strlen(m_pData->m_String) : 0;
diff --git a/core/fxcrt/cfx_bytestring_unittest.cpp b/core/fxcrt/cfx_bytestring_unittest.cpp
index a4c5187..6bbe305 100644
--- a/core/fxcrt/cfx_bytestring_unittest.cpp
+++ b/core/fxcrt/cfx_bytestring_unittest.cpp
@@ -833,6 +833,73 @@
   }
 }
 
+TEST(fxcrt, ByteStringEmptyReverseIterator) {
+  CFX_ByteString empty;
+  auto iter = empty.rbegin();
+  EXPECT_TRUE(iter == empty.rend());
+  EXPECT_FALSE(iter != empty.rend());
+  EXPECT_FALSE(iter < empty.rend());
+}
+
+TEST(fxcrt, ByteStringOneCharReverseIterator) {
+  CFX_ByteString one_str("a");
+  auto iter = one_str.rbegin();
+  EXPECT_FALSE(iter == one_str.rend());
+  EXPECT_TRUE(iter != one_str.rend());
+  EXPECT_TRUE(iter < one_str.rend());
+
+  char ch = *iter++;
+  EXPECT_EQ('a', ch);
+  EXPECT_TRUE(iter == one_str.rend());
+  EXPECT_FALSE(iter != one_str.rend());
+  EXPECT_FALSE(iter < one_str.rend());
+}
+
+TEST(fxcrt, ByteStringMultiCharReverseIterator) {
+  CFX_ByteString multi_str("abcd");
+  auto iter = multi_str.rbegin();
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  char ch = *iter++;
+  EXPECT_EQ('d', ch);
+  EXPECT_EQ('c', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *(++iter);
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('b', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter++;
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('a', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter++;
+  EXPECT_EQ('a', ch);
+  EXPECT_TRUE(iter == multi_str.rend());
+
+  ch = *(--iter);
+  EXPECT_EQ('a', ch);
+  EXPECT_EQ('a', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter--;
+  EXPECT_EQ('a', ch);
+  EXPECT_EQ('b', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter--;
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('c', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *(--iter);
+  EXPECT_EQ('d', ch);
+  EXPECT_EQ('d', *iter);
+  EXPECT_TRUE(iter == multi_str.rbegin());
+}
+
 TEST(fxcrt, ByteStringCNotNull) {
   CFX_ByteStringC string3("abc");
   CFX_ByteStringC string6("abcdef");
@@ -1200,6 +1267,73 @@
   EXPECT_EQ('a' + 'b' + 'c', sum);
 }
 
+TEST(fxcrt, ByteStringCEmptyReverseIterator) {
+  CFX_ByteStringC empty;
+  auto iter = empty.rbegin();
+  EXPECT_TRUE(iter == empty.rend());
+  EXPECT_FALSE(iter != empty.rend());
+  EXPECT_FALSE(iter < empty.rend());
+}
+
+TEST(fxcrt, ByteStringCOneCharReverseIterator) {
+  CFX_ByteStringC one_str("a");
+  auto iter = one_str.rbegin();
+  EXPECT_FALSE(iter == one_str.rend());
+  EXPECT_TRUE(iter != one_str.rend());
+  EXPECT_TRUE(iter < one_str.rend());
+
+  char ch = *iter++;
+  EXPECT_EQ('a', ch);
+  EXPECT_TRUE(iter == one_str.rend());
+  EXPECT_FALSE(iter != one_str.rend());
+  EXPECT_FALSE(iter < one_str.rend());
+}
+
+TEST(fxcrt, ByteStringCMultiCharReverseIterator) {
+  CFX_ByteStringC multi_str("abcd");
+  auto iter = multi_str.rbegin();
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  char ch = *iter++;
+  EXPECT_EQ('d', ch);
+  EXPECT_EQ('c', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *(++iter);
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('b', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter++;
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('a', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter++;
+  EXPECT_EQ('a', ch);
+  EXPECT_TRUE(iter == multi_str.rend());
+
+  ch = *(--iter);
+  EXPECT_EQ('a', ch);
+  EXPECT_EQ('a', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter--;
+  EXPECT_EQ('a', ch);
+  EXPECT_EQ('b', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter--;
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('c', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *(--iter);
+  EXPECT_EQ('d', ch);
+  EXPECT_EQ('d', *iter);
+  EXPECT_TRUE(iter == multi_str.rbegin());
+}
+
 TEST(fxcrt, ByteStringCAnyAllNoneOf) {
   CFX_ByteStringC str("aaaaaaaaaaaaaaaaab");
   EXPECT_FALSE(std::all_of(str.begin(), str.end(),
diff --git a/core/fxcrt/cfx_string_c_template.h b/core/fxcrt/cfx_string_c_template.h
index b0e17a1..9123fc2 100644
--- a/core/fxcrt/cfx_string_c_template.h
+++ b/core/fxcrt/cfx_string_c_template.h
@@ -8,6 +8,7 @@
 #define CORE_FXCRT_CFX_STRING_C_TEMPLATE_H_
 
 #include <algorithm>
+#include <iterator>
 #include <type_traits>
 #include <utility>
 #include <vector>
@@ -26,6 +27,7 @@
   using CharType = T;
   using UnsignedType = typename std::make_unsigned<CharType>::type;
   using const_iterator = const CharType*;
+  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
   CFX_StringCTemplate() : m_Ptr(nullptr), m_Length(0) {}
 
@@ -84,6 +86,13 @@
                  : nullptr;
   }
 
+  const_reverse_iterator rbegin() const {
+    return const_reverse_iterator(end());
+  }
+  const_reverse_iterator rend() const {
+    return const_reverse_iterator(begin());
+  }
+
   bool operator==(const CharType* ptr) const {
     return FXSYS_len(ptr) == m_Length &&
            FXSYS_cmp(ptr, reinterpret_cast<const CharType*>(m_Ptr.Get()),
diff --git a/core/fxcrt/cfx_widestring.h b/core/fxcrt/cfx_widestring.h
index 9922e42..595615a 100644
--- a/core/fxcrt/cfx_widestring.h
+++ b/core/fxcrt/cfx_widestring.h
@@ -8,6 +8,7 @@
 #define CORE_FXCRT_CFX_WIDESTRING_H_
 
 #include <functional>
+#include <iterator>
 #include <utility>
 
 #include "core/fxcrt/cfx_retain_ptr.h"
@@ -25,6 +26,7 @@
  public:
   using CharType = wchar_t;
   using const_iterator = const CharType*;
+  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
   CFX_WideString();
   CFX_WideString(const CFX_WideString& other);
@@ -73,6 +75,14 @@
     return m_pData ? m_pData->m_String + m_pData->m_nDataLength : nullptr;
   }
 
+  // Note: Any subsequent modification of |this| will invalidate iterators.
+  const_reverse_iterator rbegin() const {
+    return const_reverse_iterator(end());
+  }
+  const_reverse_iterator rend() const {
+    return const_reverse_iterator(begin());
+  }
+
   void clear() { m_pData.Reset(); }
 
   FX_STRSIZE GetLength() const { return m_pData ? m_pData->m_nDataLength : 0; }
diff --git a/core/fxcrt/cfx_widestring_unittest.cpp b/core/fxcrt/cfx_widestring_unittest.cpp
index 1c8aca9..6f3bc08 100644
--- a/core/fxcrt/cfx_widestring_unittest.cpp
+++ b/core/fxcrt/cfx_widestring_unittest.cpp
@@ -756,6 +756,73 @@
   }
 }
 
+TEST(fxcrt, WideStringEmptyReverseIterator) {
+  CFX_WideString empty;
+  auto iter = empty.rbegin();
+  EXPECT_TRUE(iter == empty.rend());
+  EXPECT_FALSE(iter != empty.rend());
+  EXPECT_FALSE(iter < empty.rend());
+}
+
+TEST(fxcrt, WideStringOneCharReverseIterator) {
+  CFX_WideString one_str(L"a");
+  auto iter = one_str.rbegin();
+  EXPECT_FALSE(iter == one_str.rend());
+  EXPECT_TRUE(iter != one_str.rend());
+  EXPECT_TRUE(iter < one_str.rend());
+
+  char ch = *iter++;
+  EXPECT_EQ('a', ch);
+  EXPECT_TRUE(iter == one_str.rend());
+  EXPECT_FALSE(iter != one_str.rend());
+  EXPECT_FALSE(iter < one_str.rend());
+}
+
+TEST(fxcrt, WideStringMultiCharReverseIterator) {
+  CFX_WideString multi_str(L"abcd");
+  auto iter = multi_str.rbegin();
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  char ch = *iter++;
+  EXPECT_EQ('d', ch);
+  EXPECT_EQ('c', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *(++iter);
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('b', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter++;
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('a', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter++;
+  EXPECT_EQ('a', ch);
+  EXPECT_TRUE(iter == multi_str.rend());
+
+  ch = *(--iter);
+  EXPECT_EQ('a', ch);
+  EXPECT_EQ('a', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter--;
+  EXPECT_EQ('a', ch);
+  EXPECT_EQ('b', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter--;
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('c', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *(--iter);
+  EXPECT_EQ('d', ch);
+  EXPECT_EQ('d', *iter);
+  EXPECT_TRUE(iter == multi_str.rbegin());
+}
+
 TEST(fxcrt, WideStringUTF16LE_Encode) {
   struct UTF16LEEncodeCase {
     CFX_WideString ws;
@@ -1022,6 +1089,73 @@
   EXPECT_EQ(static_cast<int32_t>(L'a' + L'b' + L'c'), sum);
 }
 
+TEST(fxcrt, WideStringCEmptyReverseIterator) {
+  CFX_WideStringC empty;
+  auto iter = empty.rbegin();
+  EXPECT_TRUE(iter == empty.rend());
+  EXPECT_FALSE(iter != empty.rend());
+  EXPECT_FALSE(iter < empty.rend());
+}
+
+TEST(fxcrt, WideStringCOneCharReverseIterator) {
+  CFX_WideStringC one_str(L"a");
+  auto iter = one_str.rbegin();
+  EXPECT_FALSE(iter == one_str.rend());
+  EXPECT_TRUE(iter != one_str.rend());
+  EXPECT_TRUE(iter < one_str.rend());
+
+  char ch = *iter++;
+  EXPECT_EQ('a', ch);
+  EXPECT_TRUE(iter == one_str.rend());
+  EXPECT_FALSE(iter != one_str.rend());
+  EXPECT_FALSE(iter < one_str.rend());
+}
+
+TEST(fxcrt, WideStringCMultiCharReverseIterator) {
+  CFX_WideStringC multi_str(L"abcd");
+  auto iter = multi_str.rbegin();
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  char ch = *iter++;
+  EXPECT_EQ('d', ch);
+  EXPECT_EQ('c', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *(++iter);
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('b', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter++;
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('a', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter++;
+  EXPECT_EQ('a', ch);
+  EXPECT_TRUE(iter == multi_str.rend());
+
+  ch = *(--iter);
+  EXPECT_EQ('a', ch);
+  EXPECT_EQ('a', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter--;
+  EXPECT_EQ('a', ch);
+  EXPECT_EQ('b', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *iter--;
+  EXPECT_EQ('b', ch);
+  EXPECT_EQ('c', *iter);
+  EXPECT_FALSE(iter == multi_str.rend());
+
+  ch = *(--iter);
+  EXPECT_EQ('d', ch);
+  EXPECT_EQ('d', *iter);
+  EXPECT_TRUE(iter == multi_str.rbegin());
+}
+
 TEST(fxcrt, WideStringCAnyAllNoneOf) {
   CFX_WideStringC str(L"aaaaaaaaaaaaaaaaab");
   EXPECT_FALSE(std::all_of(str.begin(), str.end(),