diff --git a/beetsplug/fetchart.py b/beetsplug/fetchart.py
index 763440238..70477a624 100644
--- a/beetsplug/fetchart.py
+++ b/beetsplug/fetchart.py
@@ -210,6 +210,9 @@ class ArtSource(RequestMixin):
     def fetch_image(self, candidate, plugin):
         raise NotImplementedError()
 
+    def cleanup(self, candidate):
+        pass
+
 
 class LocalArtSource(ArtSource):
     IS_LOCAL = True
@@ -291,6 +294,13 @@ class RemoteArtSource(ArtSource):
             self._log.debug(u'error fetching art: {}', exc)
             return
 
+    def cleanup(self, candidate):
+        if candidate.path:
+            try:
+                util.remove(path=candidate.path)
+            except util.FilesystemError as exc:
+                self._log.debug(u'error cleaning up tmp art: {}', exc)
+
 
 class CoverArtArchive(RemoteArtSource):
     NAME = u"Cover Art Archive"
@@ -1017,6 +1027,8 @@ class FetchArtPlugin(plugins.BeetsPlugin, RequestMixin):
                             u'using {0.LOC_STR} image {1}'.format(
                                 source, util.displayable_path(out.path)))
                         break
+                    # Remove temporary files for invalid candidates.
+                    source.cleanup(candidate)
                 if out:
                     break
 
diff --git a/beetsplug/web/__init__.py b/beetsplug/web/__init__.py
index 21ff5d94e..49149772d 100644
--- a/beetsplug/web/__init__.py
+++ b/beetsplug/web/__init__.py
@@ -177,10 +177,11 @@ class QueryConverter(PathConverter):
     """
 
     def to_python(self, value):
-        return value.split('/')
+        queries = value.split('/')
+        return [query.replace('\\', os.sep) for query in queries]
 
     def to_url(self, value):
-        return ','.join(value)
+        return ','.join([v.replace(os.sep, '\\') for v in value])
 
 
 class EverythingConverter(PathConverter):
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 5434e8b13..abb6846c6 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -118,12 +118,18 @@ New features:
 * The classes ``AlbumInfo`` and ``TrackInfo`` now have flexible attributes,
   allowing to solve :bug:`1547`. 
   Thanks to :user:`dosoe`.
+* :doc:`/plugins/web`: The query API now interprets backslashes as path
+  separators to support path queries.
+  Thanks to :user:`nmeum`.
+  :bug:`3567`
 
 Fixes:
 
-* :doc:`/plugins/fetchart`: Fixed a bug that caused fetchart to not take 
+* :doc:`/plugins/fetchart`: Fixed a bug that caused fetchart to not take
   environment variables such as proxy servers into account when making requests
   :bug:`3450`
+* :doc:`/plugins/fetchart`: Temporary files for fetched album art that fail
+  validation are now removed
 * :doc:`/plugins/inline`: In function-style field definitions that refer to
   flexible attributes, values could stick around from one function invocation
   to the next. This meant that, when displaying a list of objects, later
diff --git a/docs/plugins/web.rst b/docs/plugins/web.rst
index d416b1b7d..65d4743fb 100644
--- a/docs/plugins/web.rst
+++ b/docs/plugins/web.rst
@@ -210,7 +210,8 @@ If the server runs UNIX, you'll need to include an extra leading slash:
 ``GET /item/query/querystring``
 +++++++++++++++++++++++++++++++
 
-Returns a list of tracks matching the query. The *querystring* must be a valid query as described in :doc:`/reference/query`. ::
+Returns a list of tracks matching the query. The *querystring* must be a
+valid query as described in :doc:`/reference/query`. ::
 
     {
       "results": [
@@ -219,6 +220,11 @@ Returns a list of tracks matching the query. The *querystring* must be a valid q
       ]
     }
 
+Path elements are joined as parts of a query. For example,
+``/item/query/foo/bar`` will be converted to the query ``foo,bar``.
+To specify literal path separators in a query, use a backslash instead of a
+slash.
+
 
 ``GET /item/6/file``
 ++++++++++++++++++++