diff --git a/kml/kml_tests/serdes_tests.cpp b/kml/kml_tests/serdes_tests.cpp
index 62fce5bf74..dff0f6f0ac 100644
--- a/kml/kml_tests/serdes_tests.cpp
+++ b/kml/kml_tests/serdes_tests.cpp
@@ -123,41 +123,41 @@ char const * kTextKml =
     "</kml>";
 
 std::vector<uint8_t> const kBinKml = {
-  0x00, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3B, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0xCC, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xCD, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x24, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x06, 0x01, 0x00,
-  0x01, 0x01, 0x00, 0x02, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xE2,
-  0xAB, 0xEB, 0x96, 0xE2, 0xFE, 0x83, 0xD4, 0x11, 0x00, 0x02, 0x01, 0x00, 0x03, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xF3,
-  0xC2, 0xFB, 0xF9, 0x01, 0x9E, 0xD0, 0xC7, 0x95, 0x9B, 0x9D, 0xBD, 0xAB, 0x12, 0x00, 0x02, 0x01,
-  0x00, 0x04, 0x01, 0x00, 0x05, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0x00,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xB8, 0xBC, 0xED, 0xA7, 0x03, 0xEA, 0xA4, 0xD0, 0x9C, 0xD9,
-  0xA7, 0xBE, 0x9A, 0x19, 0x00, 0x02, 0x01, 0x00, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xE4, 0xAF, 0xA7, 0xC1,
-  0xEB, 0xA6, 0xBE, 0x9A, 0x19, 0x00, 0x02, 0x01, 0x00, 0x07, 0x01, 0x00, 0x08, 0x00, 0x54, 0x01,
-  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x0E, 0x08, 0x1B, 0x1A, 0x41, 0x0C, 0x11, 0x25,
-  0x3F, 0x00, 0x02, 0x00, 0x01, 0x08, 0x03, 0x02, 0x06, 0x01, 0x03, 0x06, 0x40, 0x05, 0x07, 0x8D,
-  0x01, 0x06, 0x05, 0x02, 0x07, 0x07, 0x71, 0x09, 0x05, 0x05, 0x0A, 0x07, 0x12, 0x0B, 0x06, 0x5E,
-  0x0D, 0x06, 0xBA, 0x01, 0x0E, 0x05, 0x04, 0x0F, 0x05, 0x75, 0x11, 0x05, 0x0D, 0x12, 0x06, 0x09,
-  0x13, 0x07, 0x4E, 0x15, 0x06, 0x91, 0x01, 0x16, 0x06, 0x0B, 0x17, 0x06, 0x73, 0x19, 0x05, 0x06,
-  0x1A, 0x08, 0x1C, 0x1B, 0x07, 0x63, 0x1D, 0x06, 0xC0, 0x01, 0x1E, 0x05, 0x07, 0x1F, 0x06, 0x77,
-  0x21, 0x06, 0x0A, 0x22, 0x07, 0x08, 0x23, 0x07, 0x49, 0x25, 0x07, 0x90, 0x01, 0x27, 0x06, 0x72,
-  0x2A, 0x08, 0x14, 0x2B, 0x06, 0x62, 0x2D, 0x06, 0xBD, 0x01, 0x32, 0x06, 0x0C, 0x33, 0x06, 0x57,
-  0x35, 0x07, 0xA1, 0x01, 0x36, 0x06, 0x0F, 0x37, 0x07, 0x76, 0x3A, 0x08, 0x31, 0x3B, 0x06, 0x68,
-  0x3D, 0x06, 0xD1, 0x01, 0x3F, 0x06, 0x79, 0x41, 0x07, 0xB8, 0x01, 0x45, 0x07, 0x8F, 0x01, 0x47,
-  0x07, 0x74, 0x4A, 0x07, 0x13, 0x53, 0x07, 0x59, 0x5A, 0x07, 0x29, 0x5B, 0x07, 0x6D, 0x62, 0x08,
-  0x10, 0x63, 0x07, 0x4B, 0x65, 0x07, 0x96, 0x01, 0x6A, 0x08, 0x18, 0x75, 0x07, 0xB7, 0x01, 0x77,
-  0x07, 0x8A, 0x01, 0x7A, 0x08, 0x3F, 0x81, 0x01, 0x08, 0x0E, 0x9A, 0x01, 0x08, 0x25, 0xAA, 0x01,
-  0x08, 0x17, 0xBA, 0x01, 0x08, 0x3E, 0xE2, 0x01, 0x08, 0x11, 0xEA, 0x01, 0x08, 0x19, 0xFA, 0x01,
-  0x08, 0x41, 0xB0, 0x01, 0xD7, 0x64, 0xD6, 0x6E, 0x37, 0x46, 0x07, 0x3D, 0xA1, 0xA8, 0x65, 0x2F,
-  0x34, 0x01, 0x83, 0xBE, 0x2E, 0x87, 0x3C, 0x64, 0x71, 0x6E, 0xA3, 0xE7, 0xCC, 0xB7, 0x8E, 0x6D,
-  0xA7, 0xE2, 0xFD, 0x13, 0xBC, 0x9A, 0x51, 0x7D, 0xF2, 0xE9, 0x17, 0x8F, 0x33, 0x91, 0x28, 0xDB,
-  0xA1, 0x22, 0x5F, 0xB3, 0x14, 0x65, 0xE9, 0x57, 0x92, 0xAC, 0x33, 0xC5, 0xF8, 0x3E, 0x37, 0x35,
-  0x00, 0x88, 0x1C, 0x96, 0x62, 0x97, 0x17, 0x09, 0xA5, 0x3F, 0x42, 0x18, 0x98, 0xD5, 0x45, 0x96,
-  0x1D, 0x0A, 0x46, 0x2C, 0xB9, 0x94, 0xFE, 0x35, 0xF7, 0x00, 0x00, 0xF4, 0x00, 0x00, 0x00, 0x00,
-  0x1A, 0xD0, 0xA2, 0xD9, 0x95, 0x6B, 0xDC, 0x69, 0xEA, 0x2D, 0x52, 0xB0, 0x43, 0xA8, 0x7C, 0xA9,
-  0x32, 0x0E, 0x01, 0x00, 0x09,
+  0x00, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x43, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0xD4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xD5, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x2C, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+  0xFF, 0x00, 0x00, 0x00, 0x00, 0x06, 0x01, 0x00, 0x01, 0x01, 0x00, 0x02, 0x01, 0x00, 0x00, 0x01,
+  0x00, 0x00, 0x00, 0x00, 0x04, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x01, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xE2, 0xAB, 0xEB, 0x96, 0xE2, 0xFE, 0x83, 0xD4, 0x11,
+  0x00, 0x02, 0x01, 0x00, 0x03, 0x00, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x05,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xF3, 0xC2, 0xFB, 0xF9, 0x01, 0x9E, 0xD0, 0xC7, 0x95,
+  0x9B, 0x9D, 0xBD, 0xAB, 0x12, 0x00, 0x02, 0x01, 0x00, 0x04, 0x01, 0x00, 0x05, 0xFF, 0xFF, 0xFF,
+  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xB8, 0xBC,
+  0xED, 0xA7, 0x03, 0xEA, 0xA4, 0xD0, 0x9C, 0xD9, 0xA7, 0xBE, 0x9A, 0x19, 0x00, 0x02, 0x01, 0x00,
+  0x06, 0x00, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0xE4, 0xAF, 0xA7, 0xC1, 0xEB, 0xA6, 0xBE, 0x9A, 0x19, 0x00, 0x02, 0x01,
+  0x00, 0x07, 0x01, 0x00, 0x08, 0x00, 0x54, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07,
+  0x0E, 0x08, 0x1B, 0x1A, 0x41, 0x0C, 0x11, 0x25, 0x3F, 0x00, 0x02, 0x00, 0x01, 0x08, 0x03, 0x02,
+  0x06, 0x01, 0x03, 0x06, 0x40, 0x05, 0x07, 0x8D, 0x01, 0x06, 0x05, 0x02, 0x07, 0x07, 0x71, 0x09,
+  0x05, 0x05, 0x0A, 0x07, 0x12, 0x0B, 0x06, 0x5E, 0x0D, 0x06, 0xBA, 0x01, 0x0E, 0x05, 0x04, 0x0F,
+  0x05, 0x75, 0x11, 0x05, 0x0D, 0x12, 0x06, 0x09, 0x13, 0x07, 0x4E, 0x15, 0x06, 0x91, 0x01, 0x16,
+  0x06, 0x0B, 0x17, 0x06, 0x73, 0x19, 0x05, 0x06, 0x1A, 0x08, 0x1C, 0x1B, 0x07, 0x63, 0x1D, 0x06,
+  0xC0, 0x01, 0x1E, 0x05, 0x07, 0x1F, 0x06, 0x77, 0x21, 0x06, 0x0A, 0x22, 0x07, 0x08, 0x23, 0x07,
+  0x49, 0x25, 0x07, 0x90, 0x01, 0x27, 0x06, 0x72, 0x2A, 0x08, 0x14, 0x2B, 0x06, 0x62, 0x2D, 0x06,
+  0xBD, 0x01, 0x32, 0x06, 0x0C, 0x33, 0x06, 0x57, 0x35, 0x07, 0xA1, 0x01, 0x36, 0x06, 0x0F, 0x37,
+  0x07, 0x76, 0x3A, 0x08, 0x31, 0x3B, 0x06, 0x68, 0x3D, 0x06, 0xD1, 0x01, 0x3F, 0x06, 0x79, 0x41,
+  0x07, 0xB8, 0x01, 0x45, 0x07, 0x8F, 0x01, 0x47, 0x07, 0x74, 0x4A, 0x07, 0x13, 0x53, 0x07, 0x59,
+  0x5A, 0x07, 0x29, 0x5B, 0x07, 0x6D, 0x62, 0x08, 0x10, 0x63, 0x07, 0x4B, 0x65, 0x07, 0x96, 0x01,
+  0x6A, 0x08, 0x18, 0x75, 0x07, 0xB7, 0x01, 0x77, 0x07, 0x8A, 0x01, 0x7A, 0x08, 0x3F, 0x81, 0x01,
+  0x08, 0x0E, 0x9A, 0x01, 0x08, 0x25, 0xAA, 0x01, 0x08, 0x17, 0xBA, 0x01, 0x08, 0x3E, 0xE2, 0x01,
+  0x08, 0x11, 0xEA, 0x01, 0x08, 0x19, 0xFA, 0x01, 0x08, 0x41, 0xB0, 0x01, 0xD7, 0x64, 0xD6, 0x6E,
+  0x37, 0x46, 0x07, 0x3D, 0xA1, 0xA8, 0x65, 0x2F, 0x34, 0x01, 0x83, 0xBE, 0x2E, 0x87, 0x3C, 0x64,
+  0x71, 0x6E, 0xA3, 0xE7, 0xCC, 0xB7, 0x8E, 0x6D, 0xA7, 0xE2, 0xFD, 0x13, 0xBC, 0x9A, 0x51, 0x7D,
+  0xF2, 0xE9, 0x17, 0x8F, 0x33, 0x91, 0x28, 0xDB, 0xA1, 0x22, 0x5F, 0xB3, 0x14, 0x65, 0xE9, 0x57,
+  0x92, 0xAC, 0x33, 0xC5, 0xF8, 0x3E, 0x37, 0x35, 0x00, 0x88, 0x1C, 0x96, 0x62, 0x97, 0x17, 0x09,
+  0xA5, 0x3F, 0x42, 0x18, 0x98, 0xD5, 0x45, 0x96, 0x1D, 0x0A, 0x46, 0x2C, 0xB9, 0x94, 0xFE, 0x35,
+  0xF7, 0x00, 0x00, 0xF4, 0x00, 0x00, 0x00, 0x00, 0x1A, 0xD0, 0xA2, 0xD9, 0x95, 0x6B, 0xDC, 0x69,
+  0xEA, 0x2D, 0x52, 0xB0, 0x43, 0xA8, 0x7C, 0xA9, 0x32, 0x0E, 0x01, 0x00, 0x09,
 };
 
 // This function can be used to generate textual representation of vector<uint8_t> like you see above.
diff --git a/kml/type_utils.hpp b/kml/type_utils.hpp
index 1676f6d2f5..3388388779 100644
--- a/kml/type_utils.hpp
+++ b/kml/type_utils.hpp
@@ -4,6 +4,7 @@
 
 #include <cstdint>
 #include <chrono>
+#include <limits>
 #include <map>
 #include <sstream>
 #include <vector>
@@ -15,9 +16,15 @@ using Timestamp = std::chrono::time_point<std::chrono::system_clock>;
 using LocalizableString = std::unordered_map<int8_t, std::string>;
 using LocalizableStringSubIndex = std::map<int8_t, uint32_t>;
 using LocalizableStringIndex = std::vector<LocalizableStringSubIndex>;
-using Id = uint64_t;
+using CategoryId = uint64_t;
+using BookmarkId = uint64_t;
+using TrackId = uint64_t;
 using LocalId = uint8_t;
 
+CategoryId constexpr kInvalidCategoryId = std::numeric_limits<CategoryId>::max();
+BookmarkId constexpr kInvalidBookmarkId = std::numeric_limits<BookmarkId>::max();
+TrackId constexpr kInvalidTrackId = std::numeric_limits<TrackId>::max();
+
 inline uint64_t ToSecondsSinceEpoch(Timestamp const & time)
 {
   auto const s = std::chrono::duration_cast<std::chrono::seconds>(time.time_since_epoch());
diff --git a/kml/types.hpp b/kml/types.hpp
index 11fde4dc03..5b6b4711a8 100644
--- a/kml/types.hpp
+++ b/kml/types.hpp
@@ -128,7 +128,7 @@ struct BookmarkData
   bool operator!=(BookmarkData const & data) const { return !operator==(data); }
 
   // Unique id.
-  Id m_id = 0;
+  BookmarkId m_id = kInvalidBookmarkId;
   // Bookmark's name.
   LocalizableString m_name;
   // Bookmark's description.
@@ -189,9 +189,9 @@ struct TrackData
   }
 
   bool operator!=(TrackData const & data) const { return !operator==(data); }
-
+  
   // Unique id.
-  Id m_id = 0;
+  TrackId m_id = kInvalidTrackId;
   // Local track id.
   LocalId m_localId = 0;
   // Track's name.
@@ -208,7 +208,8 @@ struct TrackData
 
 struct CategoryData
 {
-  DECLARE_VISITOR_AND_DEBUG_PRINT(CategoryData, visitor(m_name, "name"),
+  DECLARE_VISITOR_AND_DEBUG_PRINT(CategoryData, visitor(m_id, "id"),
+                                  visitor(m_name, "name"),
                                   visitor(m_description, "description"),
                                   visitor(m_visible, "visible"),
                                   visitor(m_authorName, "authorName"),
@@ -225,7 +226,7 @@ struct CategoryData
 
   bool operator==(CategoryData const & data) const
   {
-    return m_name == data.m_name && m_description == data.m_description &&
+    return m_id == data.m_id && m_name == data.m_name && m_description == data.m_description &&
            m_visible == data.m_visible && m_accessRules == data.m_accessRules &&
            m_authorName == data.m_authorName && m_authorId == data.m_authorId &&
            IsEqual(m_lastModified, data.m_lastModified) && m_tags == data.m_tags &&
@@ -234,6 +235,8 @@ struct CategoryData
 
   bool operator!=(CategoryData const & data) const { return !operator==(data); }
 
+  // Unique id.
+  CategoryId m_id = kInvalidCategoryId;
   // Category's name.
   LocalizableString m_name;
   // Category's description.