diff --git a/docs/contributing/contribution_quickref.rst b/docs/contributing/contribution_quickref.rst
index f5f142bea0c5..a51fd2006b7d 100644
--- a/docs/contributing/contribution_quickref.rst
+++ b/docs/contributing/contribution_quickref.rst
@@ -84,6 +84,7 @@ To run it:
 
 :ref:`More information about Linux <Building Firefox On Linux>` / :ref:`More information about MacOS <Building Firefox On MacOS>`
 
+.. _write_a_patch:
 
 To write a patch
 ----------------
diff --git a/extensions/spellcheck/docs/index.rst b/extensions/spellcheck/docs/index.rst
new file mode 100644
index 000000000000..9b4911e7c312
--- /dev/null
+++ b/extensions/spellcheck/docs/index.rst
@@ -0,0 +1,28 @@
+Adding new words to the en-US dictionary
+========================================
+
+Occasionally bugs are filed pointing out situations where perfectly
+legitimate words are missing from the English spell check dictionary in
+Firefox. This article describes the process for adding a word to the
+dictionary.
+
+The process is pretty straight-forward:
+
+#. Get a clone of mozilla-central (see :ref:`Firefox Contributors' Quick Reference`), if
+   you don't already have one, and make sure you can build it
+   successfully.
+#. Get into the dictionary sources directory using this command:
+   ``cd extensions/spellcheck/locales/en-US/hunspell/dictionary-sources``
+#. There's a special script used for editing dictionaries. The script
+   only works if you have the environment variable ``EDITOR`` set to the
+   executable of an editor program; if you don't have it set, you can use
+   ``EDITOR=vim sh edit-dictionary`` to edit using vim (or you can
+   substitute some other editor), or you can just type
+   ``sh edit-dictionary`` if you have an ``EDITOR`` already specified.
+#. Add and remove words in the dictionary file, then quit the editor.
+#. Use ``sh merge-dictionaries`` to process the dictionary changes you've
+   made.
+#. Move the revised dictionary file into position: ``mv en-US.dic ..``
+#. Build Firefox and test your updated dictionary. Once you're
+   satisfied, use the process described in :ref:`write_a_patch` to create a
+   patch.
diff --git a/extensions/spellcheck/moz.build b/extensions/spellcheck/moz.build
index 7ed9b4111618..7493edfd6285 100644
--- a/extensions/spellcheck/moz.build
+++ b/extensions/spellcheck/moz.build
@@ -13,5 +13,7 @@ if CONFIG["MOZ_WIDGET_TOOLKIT"] != "android":
 MOCHITEST_CHROME_MANIFESTS += ["tests/chrome/chrome.ini"]
 MOCHITEST_MANIFESTS += ["tests/mochitest/mochitest.ini"]
 
+SPHINX_TREES["/extensions/spellcheck"] = "docs"
+
 with Files("**"):
     BUG_COMPONENT = ("Core", "Spelling checker")
diff --git a/toolkit/docs/index.rst b/toolkit/docs/index.rst
index 808a68b280c0..52dd0b567e1f 100644
--- a/toolkit/docs/index.rst
+++ b/toolkit/docs/index.rst
@@ -25,3 +25,4 @@ This is the nascent documentation of the Toolkit code that is shared across Fire
    content/toolkit_widgets/index
    components/url-classifier/url-classifier/index
    components/extensions/webextensions/index
+   /extensions/spellcheck/index