diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0bc27c3b..375bb67f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+* Add `FILTER_TYPE` to the `GETSUBSETSTRING` request with different values : `SQL` default value, `SAFESQL` or `EXPRESSION`
+
 ## 2.7.0 - 2023-03-16
 
 * Always provide a name with the version 'not found' when fetching the list of plugin
diff --git a/lizmap_server/lizmap_service.py b/lizmap_server/lizmap_service.py
index 3419f2fd..33ab1d4b 100755
--- a/lizmap_server/lizmap_service.py
+++ b/lizmap_server/lizmap_service.py
@@ -142,12 +142,22 @@ def polygon_filter(
             return
 
         try:
+            filter_type_param = params.get('FILTER_TYPE', '').upper()
+            if filter_type_param == 'SQL':
+                filter_type = FilterType.PlainSqlQuery
+            elif filter_type_param == 'SAFESQL':
+                filter_type = FilterType.SafeSqlQuery
+            elif filter_type_param == 'EXPRESSION':
+                filter_type = FilterType.QgisExpression
+            else:
+                filter_type = FilterType.PlainSqlQuery
+
             edition_context = is_editing_context(self.server_iface.requestHandler())
             filter_polygon_config = FilterByPolygon(
                 cfg.get("filter_by_polygon"),
                 layer,
                 edition_context,
-                filter_type=FilterType.PlainSqlQuery,
+                filter_type=filter_type,
             )
             if filter_polygon_config.is_filtered():
                 if not filter_polygon_config.is_valid():
diff --git a/test/test_lizmap_service.py b/test/test_lizmap_service.py
index ca7ef756..84f855fd 100755
--- a/test/test_lizmap_service.py
+++ b/test/test_lizmap_service.py
@@ -61,7 +61,7 @@ def test_lizmap_getserversettings(client):
 
 
 def test_lizmap_service_filter_polygon_with_user(client):
-    """  Test get polygon filter with the Lizmap service with a user. """
+    """  Test get polygon filter with the Lizmap service with a user as SQL or QGIS expression. """
     project_file = "test_filter_layer_data_by_polygon_for_groups.qgs"
 
     qs = (
@@ -70,7 +70,8 @@ def test_lizmap_service_filter_polygon_with_user(client):
         "REQUEST=GETSUBSETSTRING&"
         "MAP=france_parts.qgs&"
         "LAYER=shop_bakery&"
-        "LIZMAP_USER_GROUPS=montferrier-sur-lez"
+        # "FILTER_TYPE=SQL&" SQL must be the default value when not provided
+        "LIZMAP_USER_GROUPS=montferrier-sur-lez&"
     )
     rv = client.get(qs, project_file)
     assert rv.status_code == 200
@@ -79,10 +80,22 @@ def test_lizmap_service_filter_polygon_with_user(client):
 
     b = json.loads(rv.content.decode('utf-8'))
 
+    # SQL as output, the default format
     assert b['filter'] == '"id" IN ( 68 )'
     assert b['status'] == 'success'
     assert b['polygons'].startswith('SRID=3857;MultiPolygon')
 
+    # QGIS expression
+    qs += 'FILTER_TYPE=expression&'
+    rv = client.get(qs, project_file)
+    assert rv.status_code == 200
+    assert rv.headers.get('Content-Type', '').find('application/json') == 0
+    b = json.loads(rv.content.decode('utf-8'))
+    # geom_from_wkt is a QGIS expression subset
+    assert 'geom_from_wkt' in b['filter']
+    assert b['status'] == 'success'
+    assert b['polygons'].startswith('SRID=3857;MultiPolygon')
+
 
 def test_lizmap_service_filter_polygon_without_user(client):
     """  Test get polygon filter with the Lizmap service without a user. """