diff --git a/.github/workflows/osx_tests.yml b/.github/workflows/osx_tests.yml
index c3181705..bfb2e8c6 100644
--- a/.github/workflows/osx_tests.yml
+++ b/.github/workflows/osx_tests.yml
@@ -4,7 +4,7 @@ env:
   QGIS_DEPS_VERSION: 0.4.0
 jobs:
   osx_tests:
-    runs-on: macos-latest
+    runs-on: macos-12
     steps:
       - name: Checkout MDAL
         uses: actions/checkout@v2
diff --git a/docs/source/drivers/index.rst b/docs/source/drivers/index.rst
index 71661c39..59d32027 100644
--- a/docs/source/drivers/index.rst
+++ b/docs/source/drivers/index.rst
@@ -40,3 +40,4 @@ MDAL drivers
    dfsu
    dfs2
    h2i
+   mike21
diff --git a/mdal/frmts/mdal_mike21.cpp b/mdal/frmts/mdal_mike21.cpp
index 1f63758d..16252160 100644
--- a/mdal/frmts/mdal_mike21.cpp
+++ b/mdal/frmts/mdal_mike21.cpp
@@ -133,14 +133,18 @@ bool MDAL::DriverMike21::canReadMesh( const std::string &uri )
   return true;
 }
 
-size_t MDAL::DriverMike21::getVertexCount( const std::string &line )
+void MDAL::DriverMike21::parseHeader( const std::string &line )
 {
   auto matchResults = std::smatch{};
   if ( std::regex_search( line, matchResults, mRegexHeader2012 ) )
   {
     if ( matchResults.size() > 4 )
     {
-      return std::stoi( matchResults[3].str() );
+      mDataType = matchResults[1].str();
+      mDataUnit = matchResults[2].str();
+      mVertexCount = std::stoi( matchResults[3].str() );
+      mCrs = matchResults[4].str();
+      return;
     }
   }
 
@@ -148,33 +152,11 @@ size_t MDAL::DriverMike21::getVertexCount( const std::string &line )
   {
     if ( matchResults.size() > 2 )
     {
-      return std::stoi( matchResults[1].str() );
+      mVertexCount = std::stoi( matchResults[1].str() );
+      mCrs = matchResults[2].str();
+      return;
     }
   }
-
-  return 0;
-}
-
-std::string MDAL::DriverMike21::getCrs( const std::string &line )
-{
-  auto matchResults = std::smatch{};
-  if ( std::regex_search( line, matchResults, mRegexHeader2012 ) )
-  {
-    if ( matchResults.size() > 5 )
-    {
-      return matchResults[4].str();
-    }
-  }
-
-  if ( std::regex_search( line, matchResults, mRegexHeader2011 ) )
-  {
-    if ( matchResults.size() > 3 )
-    {
-      return matchResults[2].str();
-    }
-  }
-
-  return "";
 }
 
 std::unique_ptr<MDAL::Mesh> MDAL::DriverMike21::load( const std::string &meshFile, const std::string & )
@@ -192,9 +174,8 @@ std::unique_ptr<MDAL::Mesh> MDAL::DriverMike21::load( const std::string &meshFil
     return nullptr;
   }
 
-  std::string crs = getCrs( line );
+  parseHeader( line );
 
-  size_t vertexCount = getVertexCount( line );
   size_t faceCount = 0;
   size_t maxVerticesPerFace = 2;
 
@@ -202,7 +183,7 @@ std::unique_ptr<MDAL::Mesh> MDAL::DriverMike21::load( const std::string &meshFil
 
   while ( std::getline( in, line ) )
   {
-    if ( lineNumber == vertexCount + 1 )
+    if ( lineNumber == mVertexCount + 1 )
     {
       auto matchResults = std::smatch{};
       if ( std::regex_search( line, matchResults, mRegexElementHeader ) )
@@ -236,7 +217,7 @@ std::unique_ptr<MDAL::Mesh> MDAL::DriverMike21::load( const std::string &meshFil
   }
 
   // number of lines in file does not match number of vertices and faces specifed in first and element line
-  if ( lineNumber > 2 + vertexCount + faceCount )
+  if ( lineNumber > 2 + mVertexCount + faceCount )
   {
     MDAL::Log::error( MDAL_Status::Err_InvalidData, name(), "Number of lines in file does not fit with number of vertexes and faces specified." );
     return nullptr;
@@ -245,11 +226,11 @@ std::unique_ptr<MDAL::Mesh> MDAL::DriverMike21::load( const std::string &meshFil
   in.clear();
   in.seekg( 0, std::ios::beg );
 
-  Vertices vertices( vertexCount );
+  Vertices vertices( mVertexCount );
   Faces faces( faceCount );
 
   std::map<size_t, size_t> vertexIDtoIndex;
-  std::vector<double> vertexType( vertexCount );
+  std::vector<double> vertexType( mVertexCount );
 
   std::vector<double> nativeVertexIds;
   std::vector<double> nativeFaceIds;
@@ -263,7 +244,7 @@ std::unique_ptr<MDAL::Mesh> MDAL::DriverMike21::load( const std::string &meshFil
 
   while ( std::getline( in, line ) )
   {
-    if ( 0 < lineNumber && lineNumber < vertexCount + 1 )
+    if ( 0 < lineNumber && lineNumber < mVertexCount + 1 )
     {
       chunks = regex_split( MDAL::trim( line ) );
       if ( chunks.size() != 5 )
@@ -288,10 +269,10 @@ std::unique_ptr<MDAL::Mesh> MDAL::DriverMike21::load( const std::string &meshFil
       }
 
       // in case we have gaps/reorders in native indexes, store it
-      persist_native_index( nativeVertexIds, nodeID, vertexIndex, vertexCount );
+      persist_native_index( nativeVertexIds, nodeID, vertexIndex, mVertexCount );
       parse_vertex_id_gaps( vertexIDtoIndex, vertexIndex, nodeID - 1 );
 
-      assert( vertexIndex < vertexCount );
+      assert( vertexIndex < mVertexCount );
       Vertex &vertex = vertices[vertexIndex];
       vertex.x = toDouble( chunks[1] );
       vertex.y = toDouble( chunks[2] );
@@ -300,7 +281,7 @@ std::unique_ptr<MDAL::Mesh> MDAL::DriverMike21::load( const std::string &meshFil
       vertexIndex++;
     }
 
-    if ( vertexCount + 1 < lineNumber )
+    if ( mVertexCount + 1 < lineNumber )
     {
       chunks = regex_split( MDAL::trim( line ) );
       assert( faceIndex < faceCount );
@@ -375,7 +356,13 @@ std::unique_ptr<MDAL::Mesh> MDAL::DriverMike21::load( const std::string &meshFil
   if ( !nativeVertexIds.empty() )
     MDAL::addVertexScalarDatasetGroup( mesh.get(), nativeVertexIds, "NativeVertexIds" );
 
-  mesh->setSourceCrs( crs );
+  mesh->setSourceCrs( mCrs );
+  mesh->setMetadata( "crs", mCrs );
+  if ( !mDataType.empty() )
+    mesh->setMetadata( "data_type", mDataType );
+
+  if ( !mDataUnit.empty() )
+    mesh->setMetadata( "data_unit", mDataUnit );
 
   return std::unique_ptr<Mesh>( mesh.release() );
 }
@@ -391,7 +378,15 @@ void MDAL::DriverMike21::save( const std::string &fileName, const std::string &,
     MDAL::Log::error( MDAL_Status::Err_FailToWriteToDisk, name(), "Could not open file " + fileName );
   }
 
-  std::string line = std::to_string( mesh->verticesCount() ) + " " + mesh->crs();
+  std::string line;
+
+  const std::string dataType = mesh->getMetadata( "data_type" );
+  const std::string dataUnit = mesh->getMetadata( "data_unit" );
+  if ( !dataType.empty() && !dataUnit.empty() )
+    line.append( dataType + " " + dataUnit + " " );
+
+  line.append( std::to_string( mesh->verticesCount() ) + " " + mesh->getMetadata( "crs" ) );
+
   file << line << std::endl;
 
   std::vector<double> vertexTypes;
diff --git a/mdal/frmts/mdal_mike21.hpp b/mdal/frmts/mdal_mike21.hpp
index 60c36256..b7d78e92 100644
--- a/mdal/frmts/mdal_mike21.hpp
+++ b/mdal/frmts/mdal_mike21.hpp
@@ -88,6 +88,10 @@ namespace MDAL
 
     private:
       std::string mMeshFile;
+      std::string mCrs;
+      std::string mDataType;
+      std::string mDataUnit;
+      size_t mVertexCount = 0;
       // regex for header line in form of - integer string
       const std::regex mRegexHeader2011 = std::regex( "(\\d+)\\s+(.+)(\\s+)?" );
       // regex for header line in form of - integer integer integer string
@@ -96,8 +100,7 @@ namespace MDAL
       const std::regex mRegexElementHeader = std::regex( "(\\d+)\\s+(\\d)\\s+(\\d{2})(\\s+)?" );
 
       bool canReadHeader( const std::string &line );
-      size_t getVertexCount( const std::string &line );
-      std::string getCrs( const std::string &line );
+      void parseHeader( const std::string &line );
   };
 
 } // namespace MDAL
diff --git a/tests/mdal_testutils.cpp b/tests/mdal_testutils.cpp
index 49bab897..1be85a37 100644
--- a/tests/mdal_testutils.cpp
+++ b/tests/mdal_testutils.cpp
@@ -255,6 +255,31 @@ void compareMeshFrames( MDAL_MeshH meshA, MDAL_MeshH meshB )
   EXPECT_TRUE( compareVectors( verticesA, verticesB ) );
 }
 
+void compareMeshMetadata( MDAL_MeshH meshA, MDAL_MeshH meshB )
+{
+  // Metadata count
+  const int orignal_m_count = MDAL_M_metadataCount( meshA );
+  const int saved_m_count = MDAL_M_metadataCount( meshB );
+  EXPECT_EQ( orignal_m_count, saved_m_count );
+
+  // Metadata values
+  for ( int i = 0; i < orignal_m_count; ++i )
+  {
+    const std::string keyA( MDAL_M_metadataKey( meshA, i ) );
+    const std::string valA( MDAL_M_metadataValue( meshA, i ) );
+    for ( int j = 0; j < saved_m_count; ++j )
+    {
+      const std::string keyB( MDAL_M_metadataKey( meshB, j ) );
+      const std::string valB( MDAL_M_metadataValue( meshB, j ) );
+
+      if ( keyA == keyB && valA == valB )
+        break;
+      else if ( j == saved_m_count - 1 )
+        FAIL() << "Mesh metadata do not match: " << keyA << ": " << valA;
+    }
+  }
+}
+
 std::vector<double> getCoordinates( MDAL_MeshH mesh, int verticesCount )
 {
   MDAL_MeshVertexIteratorH iterator = MDAL_M_vertexIterator( mesh );
@@ -399,7 +424,7 @@ bool compareReferenceTime( MDAL_DatasetGroupH group, const char *referenceTime )
   return std::strcmp( MDAL_G_referenceTime( group ), referenceTime ) == 0;
 }
 
-void saveAndCompareMesh( const std::string &filename, const std::string &savedFile, const std::string &driver, const std::string &meshName )
+void saveAndCompareMesh( const std::string &filename, const std::string &savedFile, const std::string &driver, const std::string &meshName, bool compareMetadata )
 {
   //test driver capability
   EXPECT_TRUE( MDAL_DR_saveMeshCapability( MDAL_driverFromName( driver.c_str() ) ) );
@@ -433,6 +458,8 @@ void saveAndCompareMesh( const std::string &filename, const std::string &savedFi
 
   // Compare saved with the original mesh
   compareMeshFrames( meshToSave, savedMesh );
+  if ( compareMetadata )
+    compareMeshMetadata( meshToSave, savedMesh );
 
   MDAL_CloseMesh( savedMesh );
 
diff --git a/tests/mdal_testutils.hpp b/tests/mdal_testutils.hpp
index bf8913df..bd4f16e6 100644
--- a/tests/mdal_testutils.hpp
+++ b/tests/mdal_testutils.hpp
@@ -62,7 +62,8 @@ bool compareVectors( const std::vector<int> &a, const std::vector<int> &b );
 
 //! Same vertices (coords), faces, edges and connectivity between them
 void compareMeshFrames( MDAL_MeshH meshA, MDAL_MeshH meshB );
-void saveAndCompareMesh( const std::string &filename, const std::string &savedFile, const std::string &driver, const std::string &meshName = "" );
+void compareMeshMetadata( MDAL_MeshH meshA, MDAL_MeshH meshB );
+void saveAndCompareMesh( const std::string &filename, const std::string &savedFile, const std::string &driver, const std::string &meshName = "", bool compareMetadata = false );
 
 //! Compare duration with millisecond precision
 bool compareDurationInHours( double h1, double h2 );
diff --git a/tests/test_mike21.cpp b/tests/test_mike21.cpp
index a3727faa..5c4a03ed 100644
--- a/tests/test_mike21.cpp
+++ b/tests/test_mike21.cpp
@@ -190,16 +190,28 @@ TEST( MeshMike21Test, ReadOdenseRough )
 
 TEST( MeshMike21Test, SaveMike21MeshToFile )
 {
+  saveAndCompareMesh(
+    test_file( "/mike21/small.mesh" ),
+    tmp_file( "/small_saved.mesh" ),
+    "Mike21",
+    "",
+    true
+  );
+
   saveAndCompareMesh(
     test_file( "/mike21/odense_rough_comparison.mesh" ),
     tmp_file( "/odense_rough_saved.mesh" ),
-    "Mike21"
+    "Mike21",
+    "",
+    true
   );
 
   saveAndCompareMesh(
     test_file( "/mike21/odense_rough_quads_comparion.mesh" ),
     tmp_file( "/odense_rough_quads_saved.mesh" ),
-    "Mike21"
+    "Mike21",
+    "",
+    true
   );
 }