diff --git a/docs/handbook/writing-your-own-image-plugin.rst b/docs/handbook/writing-your-own-image-plugin.rst
index 80138742d68..323127e5b04 100644
--- a/docs/handbook/writing-your-own-image-plugin.rst
+++ b/docs/handbook/writing-your-own-image-plugin.rst
@@ -141,6 +141,10 @@ The fields are used as follows:
     uncompressed data, in a variety of pixel formats. For more information on
     this decoder, see the description below.
 
+    A list of C decoders can be seen under codecs section of the function array
+    in :file:`_imaging.c`. Python decoders are registered within the relevant
+    plugins.
+
 **region**
     A 4-tuple specifying where to store data in the image.
 
diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index 8d1b3e9568a..ce32c39ced6 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -715,6 +715,11 @@ def tobytes(self, encoder_name="raw", *args):
 
         :param encoder_name: What encoder to use.  The default is to
                              use the standard "raw" encoder.
+
+                             A list of C encoders can be seen under
+                             codecs section of the function array in
+                             :file:`_imaging.c`. Python encoders are
+                             registered within the relevant plugins.
         :param args: Extra arguments to the encoder.
         :returns: A :py:class:`bytes` object.
         """