diff --git a/nbrmd/contentsmanager.py b/nbrmd/contentsmanager.py
index 5895be16c..df410e15a 100644
--- a/nbrmd/contentsmanager.py
+++ b/nbrmd/contentsmanager.py
@@ -1,6 +1,8 @@
 import notebook.transutils
 from notebook.services.contents.filemanager import FileContentsManager
 from tornado.web import HTTPError
+from traitlets import Unicode
+from traitlets.config import Configurable
 
 import os
 import nbrmd
@@ -25,14 +27,21 @@ def _reads(s, as_version, **kwargs):
 
 
 def check_formats(formats):
+    if isinstance(formats, str):
+        formats = formats.split(',')
+
+    formats = [fmt if fmt.startswith('.') else '.' + fmt
+               for fmt in formats if fmt != '']
+
     allowed = nbrmd.notebook_extensions
     if not isinstance(formats, list) or not set(formats).issubset(allowed):
-        raise TypeError(u"Notebook metadata 'nbrmd_formats' "
-                        u"should be subset of {}".format(str(allowed)))
+        raise TypeError("Notebook metadata 'nbrmd_formats' "
+                        "should be subset of {}, but was {}"
+                        "".format(str(allowed), str(formats)))
     return formats
 
 
-class RmdFileContentsManager(FileContentsManager):
+class RmdFileContentsManager(FileContentsManager, Configurable):
     """
     A FileContentsManager Class that reads and stores notebooks to classical
     Jupyter notebooks (.ipynb), R Markdown notebooks (.Rmd),
@@ -45,8 +54,11 @@ class RmdFileContentsManager(FileContentsManager):
     def all_nb_extensions(self):
         return ['.ipynb'] + self.nb_extensions
 
-    default_nbrmd_formats = ['.ipynb']
-    default_nbrmd_sourceonly_format = None
+    default_nbrmd_formats = Unicode(
+        u'ipynb',
+        help='Save notebooks to these file extensions. '
+             'Can be any of ipynb,Rmd,py,R, comma separated',
+        config=True)
 
     def _read_notebook(self, os_path, as_version=4,
                        load_alternative_format=True):
@@ -67,24 +79,23 @@ def _read_notebook(self, os_path, as_version=4,
         nbrmd_formats = (nb.metadata.get('nbrmd_formats') or
                          self.default_nbrmd_formats)
 
+        nbrmd_formats = check_formats(nbrmd_formats)
+
         if ext not in nbrmd_formats:
             nbrmd_formats.append(ext)
 
         nbrmd_formats = check_formats(nbrmd_formats)
 
-        # Source format is taken in metadata, contentsmanager, or is current
-        # ext, or is first non .ipynb format that is found on disk
-        source_format = (nb.metadata.get('nbrmd_sourceonly_format') or
-                         self.default_nbrmd_sourceonly_format)
-
-        if source_format is None:
-            if ext != '.ipynb':
-                source_format = ext
-            else:
-                for fmt in nbrmd_formats:
-                    if fmt != '.ipynb' and os.path.isfile(file + fmt):
-                        source_format = fmt
-                        break
+        # Source format is current ext, or is first non .ipynb format
+        # that is found on disk
+        source_format = None
+        if ext != '.ipynb':
+            source_format = ext
+        else:
+            for fmt in nbrmd_formats:
+                if fmt != '.ipynb' and os.path.isfile(file + fmt):
+                    source_format = fmt
+                    break
 
         nb_outputs = None
         if source_format is not None and ext != source_format:
@@ -120,6 +131,8 @@ def _save_notebook(self, os_path, nb):
         formats = (nb.get('metadata', {}).get('nbrmd_formats') or
                    self.default_nbrmd_formats)
 
+        formats = check_formats(formats)
+
         if org_ext not in formats:
             formats.append(org_ext)
 
diff --git a/tests/test_save_multiple.py b/tests/test_save_multiple.py
index 00a6077b2..9cda436e2 100644
--- a/tests/test_save_multiple.py
+++ b/tests/test_save_multiple.py
@@ -76,7 +76,7 @@ def test_no_files_created_on_no_format(tmpdir):
 
     cm = RmdFileContentsManager()
     cm.root_dir = str(tmpdir)
-    cm.default_nbrmd_formats = []
+    cm.default_nbrmd_formats = ''
 
     cm.save(
         model=dict(type='notebook',
@@ -109,7 +109,7 @@ def test_no_rmd_on_not_notebook(tmpdir):
 
     cm = RmdFileContentsManager()
     cm.root_dir = str(tmpdir)
-    cm.default_nbrmd_formats = ['.Rmd']
+    cm.default_nbrmd_formats = '.Rmd'
 
     with pytest.raises(HTTPError):
         cm.save(model=dict(type='not notebook',
@@ -124,7 +124,7 @@ def test_no_rmd_on_not_v4(tmpdir):
 
     cm = RmdFileContentsManager()
     cm.root_dir = str(tmpdir)
-    cm.default_nbrmd_formats = ['.Rmd']
+    cm.default_nbrmd_formats = '.Rmd'
 
     with pytest.raises(NotebookValidationError):
         cm.save(model=dict(type='notebook',
diff --git a/tests/utils.py b/tests/utils.py
index 409a11dc3..eb61d9c8e 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -31,10 +31,6 @@ def remove_outputs(nb):
         if k in nb:
             del nb[k]
 
-    for k in ['nbrmd_formats', 'nbrmd_sourceonly_format']:
-        if k in nb.metadata:
-            del nb.metadata[k]
-
     return nb