diff --git a/gallery_dl/util.py b/gallery_dl/util.py
index d85d2b37..09f851ea 100644
--- a/gallery_dl/util.py
+++ b/gallery_dl/util.py
@@ -48,12 +48,22 @@ def bdecode(data, alphabet="0123456789"):
 
 
 def advance(iterable, num):
-    """"Advance the iterable by 'num' steps"""
+    """"Advance 'iterable' by 'num' steps"""
     iterator = iter(iterable)
     next(itertools.islice(iterator, num, num), None)
     return iterator
 
 
+def unique(iterable):
+    """Yield unique elements from 'iterable' while preserving order"""
+    seen = set()
+    add = seen.add
+    for element in iterable:
+        if element not in seen:
+            add(element)
+            yield element
+
+
 def raises(cls):
     """Returns a function that raises 'cls' as exception"""
     def wrap(*args):
diff --git a/test/test_util.py b/test/test_util.py
index 08ecd643..fd659a07 100644
--- a/test/test_util.py
+++ b/test/test_util.py
@@ -446,6 +446,16 @@ class TestOther(unittest.TestCase):
         self.assertCountEqual(
             util.advance(util.advance(items, 1), 2), range(3, 5))
 
+    def test_unique(self):
+        self.assertSequenceEqual(
+            list(util.unique("")), "")
+        self.assertSequenceEqual(
+            list(util.unique("AABBCC")), "ABC")
+        self.assertSequenceEqual(
+            list(util.unique("ABABABCAABBCC")), "ABC")
+        self.assertSequenceEqual(
+            list(util.unique([1, 2, 1, 3, 2, 1])), [1, 2, 3])
+
     def test_raises(self):
         func = util.raises(Exception)
         with self.assertRaises(Exception):