diff --git a/applications/test/dictionary/testDictAPI b/applications/test/dictionary/testDictAPI
new file mode 100644
index 0000000000000000000000000000000000000000..e6091cb9d0b4aff850b3d63b0261f35ab9af5384
--- /dev/null
+++ b/applications/test/dictionary/testDictAPI
@@ -0,0 +1,19 @@
+/*--------------------------------*- C++ -*----------------------------------*\
+| =========                 |                                                 |
+| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
+|  \\    /   O peration     | Version:  v1812                                 |
+|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
+|    \\/     M anipulation  |                                                 |
+\*---------------------------------------------------------------------------*/
+FoamFile
+{
+    version     2.0;
+    format      ascii;
+    class       dictionary;
+    object      testDict;
+}
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+_FOAM_API  $FOAM_API;
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
diff --git a/applications/utilities/postProcessing/graphics/PVReaders/vtkPVFoam/vtkPVFoam.C b/applications/utilities/postProcessing/graphics/PVReaders/vtkPVFoam/vtkPVFoam.C
index 5da86f74521634301b5a315c7f5dce399070031a..7bb62bb04115f25b38ca20191a34437bb2329b41 100644
--- a/applications/utilities/postProcessing/graphics/PVReaders/vtkPVFoam/vtkPVFoam.C
+++ b/applications/utilities/postProcessing/graphics/PVReaders/vtkPVFoam/vtkPVFoam.C
@@ -310,6 +310,9 @@ Foam::vtkPVFoam::vtkPVFoam
         fullCasePath = cwd();
     }
 
+    // OPENFOAM API
+    setEnv("FOAM_API", std::to_string(OPENFOAM_PLUS), true);
+
     // The name of the executable, unless already present in the environment
     setEnv("FOAM_EXECUTABLE", "paraview", false);
 
diff --git a/applications/utilities/postProcessing/graphics/PVReaders/vtkPVblockMesh/vtkPVblockMesh.C b/applications/utilities/postProcessing/graphics/PVReaders/vtkPVblockMesh/vtkPVblockMesh.C
index 6a9037c38540e54f51f46a3ed603652210c35b1e..ef972eb9f0c90bdd46607a6264b82cfda72820c7 100644
--- a/applications/utilities/postProcessing/graphics/PVReaders/vtkPVblockMesh/vtkPVblockMesh.C
+++ b/applications/utilities/postProcessing/graphics/PVReaders/vtkPVblockMesh/vtkPVblockMesh.C
@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-     \\/     M anipulation  | Copyright (C) 2017 OpenCFD Ltd.
+     \\/     M anipulation  | Copyright (C) 2017-2019 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -206,6 +206,9 @@ Foam::vtkPVblockMesh::vtkPVblockMesh
         fullCasePath = cwd();
     }
 
+    // OPENFOAM API
+    setEnv("FOAM_API", std::to_string(OPENFOAM_PLUS), true);
+
     // The name of the executable, unless already present in the environment
     setEnv("FOAM_EXECUTABLE", "paraview", false);
 
diff --git a/etc/config.csh/unset b/etc/config.csh/unset
index 9d62c3ac3873166b6503578dc61139754d20de53..c34673ed79d215a140391753a66744abba282f47 100644
--- a/etc/config.csh/unset
+++ b/etc/config.csh/unset
@@ -3,7 +3,7 @@
 # \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
 #  \\    /   O peration     |
 #   \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-#    \\/     M anipulation  | Copyright (C) 2016-2017 OpenCFD Ltd.
+#    \\/     M anipulation  | Copyright (C) 2016-2019 OpenCFD Ltd.
 #------------------------------------------------------------------------------
 # License
 #     This file is part of OpenFOAM, licensed under GNU General Public License
@@ -72,6 +72,7 @@ unsetenv WM_THIRD_PARTY_DIR
 #------------------------------------------------------------------------------
 # Unset FOAM_* environment variables
 
+unsetenv FOAM_API
 unsetenv FOAM_APPBIN
 unsetenv FOAM_APP
 unsetenv FOAM_CODE_TEMPLATES
diff --git a/etc/config.sh/unset b/etc/config.sh/unset
index d5d4a8530e33649679fe4278d26e50ecc1b5b0b4..99c4c1330a371db8563e2eccff4b5aa430e9a312 100644
--- a/etc/config.sh/unset
+++ b/etc/config.sh/unset
@@ -3,7 +3,7 @@
 # \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
 #  \\    /   O peration     |
 #   \\  /    A nd           | Copyright (C) 2011-2016 OpenFOAM Foundation
-#    \\/     M anipulation  | Copyright (C) 2016-2017 OpenCFD Ltd.
+#    \\/     M anipulation  | Copyright (C) 2016-2019 OpenCFD Ltd.
 #------------------------------------------------------------------------------
 # License
 #     This file is part of OpenFOAM, licensed under GNU General Public License
@@ -63,6 +63,7 @@ unset WM_THIRD_PARTY_DIR
 #------------------------------------------------------------------------------
 # Unset FOAM_* environment variables
 
+unset FOAM_API
 unset FOAM_APPBIN
 unset FOAM_APP
 unset FOAM_CODE_TEMPLATES
diff --git a/src/OpenFOAM/global/argList/argList.C b/src/OpenFOAM/global/argList/argList.C
index 7054cf8c9899fd405712a1afda12ed1a1fb660c5..e72405bbe8d5571129da1ec83269c244b7aa1428 100644
--- a/src/OpenFOAM/global/argList/argList.C
+++ b/src/OpenFOAM/global/argList/argList.C
@@ -585,6 +585,9 @@ void Foam::argList::getRootCase()
     // The name of the executable, unless already present in the environment
     setEnv("FOAM_EXECUTABLE", executable_, false);
 
+    // OPENFOAM API
+    setEnv("FOAM_API", std::to_string(OPENFOAM_PLUS), true);
+
     // Set the case and case-name as an environment variable
     if (rootPath_.isAbsolute())
     {
diff --git a/src/OpenFOAM/global/argList/argList.H b/src/OpenFOAM/global/argList/argList.H
index ef4951fc72b0a01ac8c61653374738e3ae5686f8..80541d45f13e0f9cdbfb3d067f1ab1c2b918afa2 100644
--- a/src/OpenFOAM/global/argList/argList.H
+++ b/src/OpenFOAM/global/argList/argList.H
@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2011-2017 OpenFOAM Foundation
-     \\/     M anipulation  | Copyright (C) 2016-2017 OpenCFD Ltd.
+     \\/     M anipulation  | Copyright (C) 2016-2019 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -57,6 +57,8 @@ Description
     may be present for some solvers or utilities.
 
     Environment variables set by argList or by Time:
+      - \par FOAM_API
+        The value of the OPENFOAM compiler define
       - \par FOAM_CASE
         The path of the global case.
         It is the same for serial and parallel jobs.