diff --git a/apps/openmw_test_suite/esm/testrefid.cpp b/apps/openmw_test_suite/esm/testrefid.cpp
index 4fb62bcb62..6c7afb05cc 100644
--- a/apps/openmw_test_suite/esm/testrefid.cpp
+++ b/apps/openmw_test_suite/esm/testrefid.cpp
@@ -342,6 +342,12 @@ namespace ESM
             static RefId call() { return RefId::index(REC_BOOK, 7); }
         };
 
+        template <>
+        struct GenerateRefId<ESM3ExteriorCellRefId>
+        {
+            static RefId call() { return RefId::esm3ExteriorCell(-12, 7); }
+        };
+
         template <class T>
         struct ESMRefIdTypesTest : Test
         {
diff --git a/apps/openmw_test_suite/esm3/testsaveload.cpp b/apps/openmw_test_suite/esm3/testsaveload.cpp
index 049fcb6f1d..8742495b3b 100644
--- a/apps/openmw_test_suite/esm3/testsaveload.cpp
+++ b/apps/openmw_test_suite/esm3/testsaveload.cpp
@@ -248,16 +248,10 @@ namespace ESM
             record.mObject.mRef.mRefID = generateRandomRefId();
             std::generate_n(std::inserter(record.mPreviousItems, record.mPreviousItems.end()), 2,
                 [&] { return std::make_pair(generateRandomRefId(), generateRandomRefId()); });
-            record.mCellId.mWorldspace = "worldspace1";
-            record.mCellId.mIndex.mX = 42;
-            record.mCellId.mIndex.mY = 13;
-            record.mCellId.mPaged = true;
+            record.mCellId = ESM::RefId::esm3ExteriorCell(0, 0);
             generateArray(record.mLastKnownExteriorPosition);
             record.mHasMark = true;
-            record.mMarkedCell.mWorldspace = "worldspace2";
-            record.mMarkedCell.mIndex.mX = 0;
-            record.mMarkedCell.mIndex.mY = 0;
-            record.mMarkedCell.mPaged = false;
+            record.mMarkedCell = ESM::RefId::esm3ExteriorCell(0, 0);
             generateArray(record.mMarkedPosition.pos);
             generateArray(record.mMarkedPosition.rot);
             record.mCurrentCrimeId = 42;
@@ -267,16 +261,11 @@ namespace ESM
             EXPECT_EQ(record.mBirthsign, result.mBirthsign);
             EXPECT_EQ(record.mPreviousItems, result.mPreviousItems);
             EXPECT_EQ(record.mPreviousItems, result.mPreviousItems);
-            EXPECT_EQ(record.mCellId.mWorldspace, result.mCellId.mWorldspace);
-            EXPECT_EQ(record.mCellId.mIndex.mX, result.mCellId.mIndex.mX);
-            EXPECT_EQ(record.mCellId.mIndex.mY, result.mCellId.mIndex.mY);
-            EXPECT_EQ(record.mCellId.mPaged, result.mCellId.mPaged);
+            EXPECT_EQ(record.mCellId, result.mCellId);
+
             EXPECT_THAT(record.mLastKnownExteriorPosition, ElementsAreArray(result.mLastKnownExteriorPosition));
             EXPECT_EQ(record.mHasMark, result.mHasMark);
-            EXPECT_EQ(record.mMarkedCell.mWorldspace, result.mMarkedCell.mWorldspace);
-            EXPECT_EQ(record.mMarkedCell.mIndex.mX, result.mMarkedCell.mIndex.mX);
-            EXPECT_EQ(record.mMarkedCell.mIndex.mY, result.mMarkedCell.mIndex.mY);
-            EXPECT_EQ(record.mMarkedCell.mPaged, result.mMarkedCell.mPaged);
+            EXPECT_EQ(record.mMarkedCell, result.mMarkedCell);
             EXPECT_THAT(record.mMarkedPosition.pos, ElementsAreArray(result.mMarkedPosition.pos));
             EXPECT_THAT(record.mMarkedPosition.rot, ElementsAreArray(result.mMarkedPosition.rot));
             EXPECT_EQ(record.mCurrentCrimeId, result.mCurrentCrimeId);
diff --git a/components/esm/esm3exteriorcellrefid.cpp b/components/esm/esm3exteriorcellrefid.cpp
index c4c210032a..72b540cfdb 100644
--- a/components/esm/esm3exteriorcellrefid.cpp
+++ b/components/esm/esm3exteriorcellrefid.cpp
@@ -1,4 +1,5 @@
 #include "esm3exteriorcellrefid.hpp"
+#include "serializerefid.hpp"
 
 #include <ostream>
 #include <sstream>
@@ -7,16 +8,25 @@ namespace ESM
 {
     std::string ESM3ExteriorCellRefId::toString() const
     {
-        std::ostringstream stream;
-        stream << "# " << mY << ", " << mY;
-        return stream.str();
+        std::string result;
+        std::size_t integralSizeX = getIntegralSize(mX);
+        result.resize(integralSizeX + getIntegralSize(mY) + 3, '\0');
+        serializeIntegral(mX, 0, result);
+        result[integralSizeX] = ':';
+        serializeIntegral(mY, integralSizeX + 1, result);
+        return result;
     }
 
     std::string ESM3ExteriorCellRefId::toDebugString() const
     {
-        std::ostringstream stream;
-        stream << *this;
-        return stream.str();
+        std::string result;
+        std::size_t integralSizeX = getIntegralSize(mX);
+
+        serializeRefIdPrefix(integralSizeX + getIntegralSize(mY) + 1, esm3ExteriorCellRefIdPrefix, result);
+        serializeIntegral(mX, esm3ExteriorCellRefIdPrefix.size(), result);
+        result[esm3ExteriorCellRefIdPrefix.size() + integralSizeX] = ':';
+        serializeIntegral(mY, esm3ExteriorCellRefIdPrefix.size() + integralSizeX + 1, result);
+        return result;
     }
 
     std::ostream& operator<<(std::ostream& stream, ESM3ExteriorCellRefId value)
diff --git a/components/esm/refid.cpp b/components/esm/refid.cpp
index d04ad4a845..880b6da7e2 100644
--- a/components/esm/refid.cpp
+++ b/components/esm/refid.cpp
@@ -237,6 +237,13 @@ namespace ESM
             return ESM::RefId::index(recordType,
                 deserializeIntegral<std::uint32_t>(indexRefIdPrefix.size() + sizeof(recordType) + 1, value));
         }
+        if (value.starts_with(esm3ExteriorCellRefIdPrefix))
+        {
+            std::int32_t x = deserializeIntegral<std::int32_t>(esm3ExteriorCellRefIdPrefix.size(), value);
+            std::int32_t y
+                = deserializeIntegral<std::int32_t>(esm3ExteriorCellRefIdPrefix.size() + getIntegralSize(x) + 1, value);
+            return ESM::ESM3ExteriorCellRefId(x, y);
+        }
 
         return ESM::RefId::stringRefId(value);
     }
diff --git a/components/esm/refid.hpp b/components/esm/refid.hpp
index e4b97ceb7b..3fafdb0b74 100644
--- a/components/esm/refid.hpp
+++ b/components/esm/refid.hpp
@@ -50,7 +50,8 @@ namespace ESM
     public:
         const static RefId sEmpty;
 
-        using Value = std::variant<EmptyRefId, StringRefId, FormIdRefId, GeneratedRefId, IndexRefId>;
+        using Value
+            = std::variant<EmptyRefId, StringRefId, FormIdRefId, GeneratedRefId, IndexRefId, ESM3ExteriorCellRefId>;
 
         // Constructs RefId from a serialized string containing byte by byte copy of RefId::mValue.
         static ESM::RefId deserialize(std::string_view value);
diff --git a/components/esm/serializerefid.hpp b/components/esm/serializerefid.hpp
index 9f43511622..d8c5fa982a 100644
--- a/components/esm/serializerefid.hpp
+++ b/components/esm/serializerefid.hpp
@@ -12,6 +12,7 @@ namespace ESM
     constexpr std::string_view formIdRefIdPrefix = "FormId:";
     constexpr std::string_view generatedRefIdPrefix = "Generated:";
     constexpr std::string_view indexRefIdPrefix = "Index:";
+    constexpr std::string_view esm3ExteriorCellRefIdPrefix = "Esm3ExteriorCell:";
 
     template <class T>
     std::size_t getIntegralSize(T value)