diff --git a/backend/app_sdk/app_base.py b/backend/app_sdk/app_base.py
index 2c6cbc90..78f993f8 100755
--- a/backend/app_sdk/app_base.py
+++ b/backend/app_sdk/app_base.py
@@ -298,6 +298,17 @@ def url_encode(base):
 
     return quote(base)
 
+@shuffle_filters.register
+def url_decode(base):
+    """url-decode a string"""
+    try:
+        from urllib import unquote_plus
+    except ImportError:
+        from urllib.parse import unquote_plus
+
+    return unquote_plus(base)
+
+
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