diff --git a/client/html/help_search_posts.tpl b/client/html/help_search_posts.tpl
index a9e1a8e..85dffce 100644
--- a/client/html/help_search_posts.tpl
+++ b/client/html/help_search_posts.tpl
@@ -70,6 +70,10 @@
             <td><code>type</code></td>
             <td>given type of posts. <code>&lt;value&gt;</code> can be either <code>image</code>, <code>animation</code> (or <code>animated</code> or <code>anim</code>), <code>flash</code> (or <code>swf</code>) or <code>video</code> (or <code>webm</code>).</td>
         </tr>
+        <tr>
+            <td><code>flag</code></td>
+            <td>having given flag. <code>&lt;value&gt;</code> can be either <code>loop</code> or <code>sound</code>.</td>
+        </tr>
         <tr>
             <td><code>content-checksum</code></td>
             <td>having given SHA1 checksum</td>
diff --git a/server/szurubooru/func/posts.py b/server/szurubooru/func/posts.py
index 4fcc087..a10780c 100644
--- a/server/szurubooru/func/posts.py
+++ b/server/szurubooru/func/posts.py
@@ -222,7 +222,7 @@ class PostSerializer(serialization.BaseSerializer):
         return get_post_thumbnail_url(self.post)
 
     def serialize_flags(self) -> Any:
-        return self.post.flags
+        return [x for x in self.post.flags.split(',') if x]
 
     def serialize_tags(self) -> Any:
         return [
@@ -356,7 +356,7 @@ def create_post(
     post.safety = model.Post.SAFETY_SAFE
     post.user = user
     post.creation_time = datetime.utcnow()
-    post.flags = []
+    post.flags = ''
 
     post.type = ''
     post.checksum = ''
@@ -628,7 +628,7 @@ def update_post_flags(post: model.Post, flags: List[str]) -> None:
             raise InvalidPostFlagError(
                 'Flag must be one of %r.' % list(FLAG_MAP.values()))
         target_flags.append(flag)
-    post.flags = target_flags
+    post.flags = ','.join(target_flags)
 
 
 def feature_post(post: model.Post, user: Optional[model.User]) -> None:
diff --git a/server/szurubooru/func/snapshots.py b/server/szurubooru/func/snapshots.py
index 240c3bc..b6a13e0 100644
--- a/server/szurubooru/func/snapshots.py
+++ b/server/szurubooru/func/snapshots.py
@@ -29,7 +29,7 @@ def get_post_snapshot(post: model.Post) -> Dict[str, Any]:
         'source': post.source,
         'safety': post.safety,
         'checksum': post.checksum,
-        'flags': post.flags,
+        'flags': sorted(post.flags.split(',')),
         'featured': post.is_featured,
         'tags': sorted([tag.first_name for tag in post.tags]),
         'relations': sorted([rel.post_id for rel in post.relations]),
diff --git a/server/szurubooru/migrations/versions/1cd4c7b22846_change_flags_column_to_string.py b/server/szurubooru/migrations/versions/1cd4c7b22846_change_flags_column_to_string.py
new file mode 100644
index 0000000..04e0764
--- /dev/null
+++ b/server/szurubooru/migrations/versions/1cd4c7b22846_change_flags_column_to_string.py
@@ -0,0 +1,63 @@
+'''
+Change flags column to string
+
+Revision ID: 1cd4c7b22846
+Created at: 2018-09-21 19:37:27.686568
+'''
+
+import sqlalchemy as sa
+from alembic import op
+
+revision = '1cd4c7b22846'
+down_revision = 'a39c7f98a7fa'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    conn = op.get_bind()
+    op.alter_column('post', 'flags', new_column_name='oldflags')
+    op.add_column('post', sa.Column(
+        'flags', sa.Unicode(200), default='', nullable=True))
+    posts = sa.Table(
+        'post',
+        sa.MetaData(),
+        sa.Column('id', sa.Integer, primary_key=True),
+        sa.Column('flags', sa.Unicode(200), default='', nullable=True),
+        sa.Column('oldflags', sa.PickleType(), nullable=True),
+    )
+    for row in conn.execute(posts.select()):
+        newflag = ','.join(row.oldflags)
+        conn.execute(
+            # pylint: disable=no-value-for-parameter
+            posts.update().where(
+                posts.c.id == row.id
+            ).values(
+                flags=newflag
+            )
+        )
+    op.drop_column('post', 'oldflags')
+
+
+def downgrade():
+    conn = op.get_bind()
+    op.alter_column('post', 'flags', new_column_name='oldflags')
+    op.add_column('post', sa.Column('flags', sa.PickleType(), nullable=True))
+    posts = sa.Table(
+        'post',
+        sa.MetaData(),
+        sa.Column('id', sa.Integer, primary_key=True),
+        sa.Column('flags', sa.PickleType(), nullable=True),
+        sa.Column('oldflags', sa.Unicode(200), default='', nullable=True),
+    )
+    for row in conn.execute(posts.select()):
+        newflag = [x for x in row.oldflags.split(',') if x]
+        conn.execute(
+            # pylint: disable=no-value-for-parameter
+            posts.update().where(
+                posts.c.id == row.id
+            ).values(
+                flags=newflag
+            )
+        )
+    op.drop_column('post', 'oldflags')
diff --git a/server/szurubooru/model/post.py b/server/szurubooru/model/post.py
index d682c1b..c0e3b13 100644
--- a/server/szurubooru/model/post.py
+++ b/server/szurubooru/model/post.py
@@ -169,7 +169,7 @@ class Post(Base):
     last_edit_time = sa.Column('last_edit_time', sa.DateTime)
     safety = sa.Column('safety', sa.Unicode(32), nullable=False)
     source = sa.Column('source', sa.Unicode(200))
-    flags = sa.Column('flags', sa.PickleType, default=None)
+    flags = sa.Column('flags', sa.Unicode(200), default='')
 
     # content description
     type = sa.Column('type', sa.Unicode(32), nullable=False)
diff --git a/server/szurubooru/search/configs/post_search_config.py b/server/szurubooru/search/configs/post_search_config.py
index 8baa0dd..3d5b0ee 100644
--- a/server/szurubooru/search/configs/post_search_config.py
+++ b/server/szurubooru/search/configs/post_search_config.py
@@ -35,6 +35,14 @@ def _safety_transformer(value: str) -> str:
     return search_util.enum_transformer(available_values, value)
 
 
+def _flag_transformer(value: str) -> str:
+    available_values = {
+        'loop': model.Post.FLAG_LOOP,
+        'sound': model.Post.FLAG_SOUND,
+    }
+    return '%' + search_util.enum_transformer(available_values, value) + '%'
+
+
 def _create_score_filter(score: int) -> Filter:
     def wrapper(
             query: SaQuery,
@@ -326,6 +334,12 @@ class PostSearchConfig(BaseSearchConfig):
                 ['note-text'],
                 _note_filter
             ),
+
+            (
+                ['flag'],
+                search_util.create_str_filter(
+                    model.Post.flags, _flag_transformer)
+            ),
         ])
 
     @property