diff --git a/API.md b/API.md
index 8d4eccd8..da2edd68 100644
--- a/API.md
+++ b/API.md
@@ -10,6 +10,7 @@
    - [Basic requests](#basic-requests)
    - [File uploads](#file-uploads)
    - [Error handling](#error-handling)
+   - [Field selecting](#field-selecting)
 
 2. [API reference](#api-reference)
 
@@ -121,6 +122,21 @@ code together with JSON of following structure:
 }
 ```
 
+## Field selecting
+
+For performance considerations, sometimes the client might want to choose the
+fields the server sends to it in order to improve the query speed. This
+customization is available for top-level fields of most of the
+[resources](#resources). To choose the fields, the client should pass
+`?_fields=field1,field2,...` suffix to the query. This works regardless of the
+requesttype (`GET`, `PUT` etc.).
+
+For example, to list posts while getting only their IDs and tags, the client
+should send a `GET` query like this:
+
+```
+GET /posts/?_fields=id,tags
+```
 
 
 # API reference
diff --git a/server/szurubooru/api/comment_api.py b/server/szurubooru/api/comment_api.py
index 8aeaceca..e25ce606 100644
--- a/server/szurubooru/api/comment_api.py
+++ b/server/szurubooru/api/comment_api.py
@@ -1,7 +1,13 @@
 import datetime
 from szurubooru import search
 from szurubooru.api.base_api import BaseApi
-from szurubooru.func import auth, comments, posts, scores
+from szurubooru.func import auth, comments, posts, scores, util
+
+def _serialize(ctx, comment, **kwargs):
+    return comments.serialize_comment(
+        comment,
+        ctx.user,
+        options=util.get_serialization_options(ctx), **kwargs)
 
 class CommentListApi(BaseApi):
     def __init__(self):
@@ -13,7 +19,7 @@ class CommentListApi(BaseApi):
         auth.verify_privilege(ctx.user, 'comments:list')
         return self._search_executor.execute_and_serialize(
             ctx,
-            lambda comment: comments.serialize_comment(comment, ctx.user))
+            lambda comment: _serialize(ctx, comment))
 
     def post(self, ctx):
         auth.verify_privilege(ctx.user, 'comments:create')
@@ -23,13 +29,13 @@ class CommentListApi(BaseApi):
         comment = comments.create_comment(ctx.user, post, text)
         ctx.session.add(comment)
         ctx.session.commit()
-        return comments.serialize_comment(comment, ctx.user)
+        return _serialize(ctx, comment)
 
 class CommentDetailApi(BaseApi):
     def get(self, ctx, comment_id):
         auth.verify_privilege(ctx.user, 'comments:view')
         comment = comments.get_comment_by_id(comment_id)
-        return comments.serialize_comment(comment, ctx.user)
+        return _serialize(ctx, comment)
 
     def put(self, ctx, comment_id):
         comment = comments.get_comment_by_id(comment_id)
@@ -39,7 +45,7 @@ class CommentDetailApi(BaseApi):
         comment.last_edit_time = datetime.datetime.now()
         comments.update_comment_text(comment, text)
         ctx.session.commit()
-        return comments.serialize_comment(comment, ctx.user)
+        return _serialize(ctx, comment)
 
     def delete(self, ctx, comment_id):
         comment = comments.get_comment_by_id(comment_id)
@@ -56,11 +62,11 @@ class CommentScoreApi(BaseApi):
         comment = comments.get_comment_by_id(comment_id)
         scores.set_score(comment, ctx.user, score)
         ctx.session.commit()
-        return comments.serialize_comment(comment, ctx.user)
+        return _serialize(ctx, comment)
 
     def delete(self, ctx, comment_id):
         auth.verify_privilege(ctx.user, 'comments:score')
         comment = comments.get_comment_by_id(comment_id)
         scores.delete_score(comment, ctx.user)
         ctx.session.commit()
-        return comments.serialize_comment(comment, ctx.user)
+        return _serialize(ctx, comment)
diff --git a/server/szurubooru/api/context.py b/server/szurubooru/api/context.py
index b1da7287..93db39f7 100644
--- a/server/szurubooru/api/context.py
+++ b/server/szurubooru/api/context.py
@@ -9,6 +9,7 @@ class Context(object):
         self.files = {}
         self.input = {}
         self.output = None
+        self.settings = {}
 
     def has_param(self, name):
         return name in self.input
diff --git a/server/szurubooru/api/post_api.py b/server/szurubooru/api/post_api.py
index 3f0eb941..1496952d 100644
--- a/server/szurubooru/api/post_api.py
+++ b/server/szurubooru/api/post_api.py
@@ -1,7 +1,13 @@
 import datetime
 from szurubooru import search
 from szurubooru.api.base_api import BaseApi
-from szurubooru.func import auth, tags, posts, snapshots, favorites, scores
+from szurubooru.func import auth, tags, posts, snapshots, favorites, scores, util
+
+def _serialize_post(ctx, post):
+    return posts.serialize_post(
+        post,
+        ctx.user,
+        options=util.get_serialization_options(ctx))
 
 class PostListApi(BaseApi):
     def __init__(self):
@@ -12,7 +18,7 @@ class PostListApi(BaseApi):
         auth.verify_privilege(ctx.user, 'posts:list')
         self._search_executor.config.user = ctx.user
         return self._search_executor.execute_and_serialize(
-            ctx, lambda post: posts.serialize_post(post, ctx.user))
+            ctx, lambda post: _serialize_post(ctx, post))
 
     def post(self, ctx):
         auth.verify_privilege(ctx.user, 'posts:create')
@@ -38,13 +44,13 @@ class PostListApi(BaseApi):
         snapshots.save_entity_creation(post, ctx.user)
         ctx.session.commit()
         tags.export_to_json()
-        return posts.serialize_post(post, ctx.user)
+        return _serialize_post(ctx, post)
 
 class PostDetailApi(BaseApi):
     def get(self, ctx, post_id):
         auth.verify_privilege(ctx.user, 'posts:view')
         post = posts.get_post_by_id(post_id)
-        return posts.serialize_post(post, ctx.user)
+        return _serialize_post(ctx, post)
 
     def put(self, ctx, post_id):
         post = posts.get_post_by_id(post_id)
@@ -79,7 +85,7 @@ class PostDetailApi(BaseApi):
         snapshots.save_entity_modification(post, ctx.user)
         ctx.session.commit()
         tags.export_to_json()
-        return posts.serialize_post(post, ctx.user)
+        return _serialize_post(ctx, post)
 
     def delete(self, ctx, post_id):
         auth.verify_privilege(ctx.user, 'posts:delete')
@@ -104,11 +110,11 @@ class PostFeatureApi(BaseApi):
             snapshots.save_entity_modification(featured_post, ctx.user)
         snapshots.save_entity_modification(post, ctx.user)
         ctx.session.commit()
-        return posts.serialize_post(post, ctx.user)
+        return _serialize_post(ctx, post)
 
     def get(self, ctx):
         post = posts.try_get_featured_post()
-        return posts.serialize_post(post, ctx.user)
+        return _serialize_post(ctx, post)
 
 class PostScoreApi(BaseApi):
     def put(self, ctx, post_id):
@@ -117,14 +123,14 @@ class PostScoreApi(BaseApi):
         score = ctx.get_param_as_int('score', required=True)
         scores.set_score(post, ctx.user, score)
         ctx.session.commit()
-        return posts.serialize_post(post, ctx.user)
+        return _serialize_post(ctx, post)
 
     def delete(self, ctx, post_id):
         auth.verify_privilege(ctx.user, 'posts:score')
         post = posts.get_post_by_id(post_id)
         scores.delete_score(post, ctx.user)
         ctx.session.commit()
-        return posts.serialize_post(post, ctx.user)
+        return _serialize_post(ctx, post)
 
 class PostFavoriteApi(BaseApi):
     def post(self, ctx, post_id):
@@ -132,11 +138,11 @@ class PostFavoriteApi(BaseApi):
         post = posts.get_post_by_id(post_id)
         favorites.set_favorite(post, ctx.user)
         ctx.session.commit()
-        return posts.serialize_post(post, ctx.user)
+        return _serialize_post(ctx, post)
 
     def delete(self, ctx, post_id):
         auth.verify_privilege(ctx.user, 'posts:favorite')
         post = posts.get_post_by_id(post_id)
         favorites.unset_favorite(post, ctx.user)
         ctx.session.commit()
-        return posts.serialize_post(post, ctx.user)
+        return _serialize_post(ctx, post)
diff --git a/server/szurubooru/api/tag_api.py b/server/szurubooru/api/tag_api.py
index 65cecf90..372db1a9 100644
--- a/server/szurubooru/api/tag_api.py
+++ b/server/szurubooru/api/tag_api.py
@@ -1,7 +1,11 @@
 import datetime
 from szurubooru import db, search
 from szurubooru.api.base_api import BaseApi
-from szurubooru.func import auth, tags, snapshots
+from szurubooru.func import auth, tags, util, snapshots
+
+def _serialize(ctx, tag):
+    return tags.serialize_tag(
+        tag, options=util.get_serialization_options(ctx))
 
 def _create_if_needed(tag_names, user):
     if not tag_names:
@@ -20,7 +24,7 @@ class TagListApi(BaseApi):
     def get(self, ctx):
         auth.verify_privilege(ctx.user, 'tags:list')
         return self._search_executor.execute_and_serialize(
-            ctx, tags.serialize_tag)
+            ctx, lambda tag: _serialize(ctx, tag))
 
     def post(self, ctx):
         auth.verify_privilege(ctx.user, 'tags:create')
@@ -41,13 +45,13 @@ class TagListApi(BaseApi):
         snapshots.save_entity_creation(tag, ctx.user)
         ctx.session.commit()
         tags.export_to_json()
-        return tags.serialize_tag(tag)
+        return _serialize(ctx, tag)
 
 class TagDetailApi(BaseApi):
     def get(self, ctx, tag_name):
         auth.verify_privilege(ctx.user, 'tags:view')
         tag = tags.get_tag_by_name(tag_name)
-        return tags.serialize_tag(tag)
+        return _serialize(ctx, tag)
 
     def put(self, ctx, tag_name):
         tag = tags.get_tag_by_name(tag_name)
@@ -73,7 +77,7 @@ class TagDetailApi(BaseApi):
         snapshots.save_entity_modification(tag, ctx.user)
         ctx.session.commit()
         tags.export_to_json()
-        return tags.serialize_tag(tag)
+        return _serialize(ctx, tag)
 
     def delete(self, ctx, tag_name):
         tag = tags.get_tag_by_name(tag_name)
@@ -101,7 +105,7 @@ class TagMergeApi(BaseApi):
         tags.merge_tags(source_tag, target_tag)
         ctx.session.commit()
         tags.export_to_json()
-        return tags.serialize_tag(target_tag)
+        return _serialize(ctx, target_tag)
 
 class TagSiblingsApi(BaseApi):
     def get(self, ctx, tag_name):
@@ -111,7 +115,7 @@ class TagSiblingsApi(BaseApi):
         serialized_siblings = []
         for sibling, occurrences in result:
             serialized_siblings.append({
-                'tag': tags.serialize_tag(sibling),
+                'tag': _serialize(ctx, sibling),
                 'occurrences': occurrences
             })
         return {'results': serialized_siblings}
diff --git a/server/szurubooru/api/tag_category_api.py b/server/szurubooru/api/tag_category_api.py
index ffae5e0c..04b4fa18 100644
--- a/server/szurubooru/api/tag_category_api.py
+++ b/server/szurubooru/api/tag_category_api.py
@@ -1,14 +1,16 @@
 from szurubooru.api.base_api import BaseApi
-from szurubooru.func import auth, tags, tag_categories, snapshots
+from szurubooru.func import auth, tags, tag_categories, util, snapshots
+
+def _serialize(ctx, category):
+    return tag_categories.serialize_category(
+        category, options=util.get_serialization_options(ctx))
 
 class TagCategoryListApi(BaseApi):
     def get(self, ctx):
         auth.verify_privilege(ctx.user, 'tag_categories:list')
         categories = tag_categories.get_all_categories()
         return {
-            'results': [
-                tag_categories.serialize_category(category) \
-                    for category in categories],
+            'results': [_serialize(ctx, category) for category in categories],
         }
 
     def post(self, ctx):
@@ -21,13 +23,13 @@ class TagCategoryListApi(BaseApi):
         snapshots.save_entity_creation(category, ctx.user)
         ctx.session.commit()
         tags.export_to_json()
-        return tag_categories.serialize_category(category)
+        return _serialize(ctx, category)
 
 class TagCategoryDetailApi(BaseApi):
     def get(self, ctx, category_name):
         auth.verify_privilege(ctx.user, 'tag_categories:view')
         category = tag_categories.get_category_by_name(category_name)
-        return tag_categories.serialize_category(category)
+        return _serialize(ctx, category)
 
     def put(self, ctx, category_name):
         category = tag_categories.get_category_by_name(category_name)
@@ -43,7 +45,7 @@ class TagCategoryDetailApi(BaseApi):
         snapshots.save_entity_modification(category, ctx.user)
         ctx.session.commit()
         tags.export_to_json()
-        return tag_categories.serialize_category(category)
+        return _serialize(ctx, category)
 
     def delete(self, ctx, category_name):
         category = tag_categories.get_category_by_name(category_name)
@@ -69,4 +71,4 @@ class DefaultTagCategoryApi(BaseApi):
         snapshots.save_entity_modification(category, ctx.user)
         ctx.session.commit()
         tags.export_to_json()
-        return tag_categories.serialize_category(category)
+        return _serialize(ctx, category)
diff --git a/server/szurubooru/api/user_api.py b/server/szurubooru/api/user_api.py
index 29371ce6..b7d5bd00 100644
--- a/server/szurubooru/api/user_api.py
+++ b/server/szurubooru/api/user_api.py
@@ -1,6 +1,13 @@
 from szurubooru import search
 from szurubooru.api.base_api import BaseApi
-from szurubooru.func import auth, users
+from szurubooru.func import auth, users, util
+
+def _serialize(ctx, user, **kwargs):
+    return users.serialize_user(
+        user,
+        ctx.user,
+        options=util.get_serialization_options(ctx),
+        **kwargs)
 
 class UserListApi(BaseApi):
     def __init__(self):
@@ -10,7 +17,7 @@ class UserListApi(BaseApi):
     def get(self, ctx):
         auth.verify_privilege(ctx.user, 'users:list')
         return self._search_executor.execute_and_serialize(
-            ctx, lambda user: users.serialize_user(user, ctx.user))
+            ctx, lambda user: _serialize(ctx, user))
 
     def post(self, ctx):
         auth.verify_privilege(ctx.user, 'users:create')
@@ -28,13 +35,13 @@ class UserListApi(BaseApi):
                 ctx.get_file('avatar'))
         ctx.session.add(user)
         ctx.session.commit()
-        return users.serialize_user(user, ctx.user, force_show_email=True)
+        return _serialize(ctx, user, force_show_email=True)
 
 class UserDetailApi(BaseApi):
     def get(self, ctx, user_name):
         auth.verify_privilege(ctx.user, 'users:view')
         user = users.get_user_by_name(user_name)
-        return users.serialize_user(user, ctx.user)
+        return _serialize(ctx, user)
 
     def put(self, ctx, user_name):
         user = users.get_user_by_name(user_name)
@@ -60,7 +67,7 @@ class UserDetailApi(BaseApi):
                 ctx.get_param_as_string('avatarStyle'),
                 ctx.get_file('avatar'))
         ctx.session.commit()
-        return users.serialize_user(user, ctx.user)
+        return _serialize(ctx, user)
 
     def delete(self, ctx, user_name):
         user = users.get_user_by_name(user_name)
diff --git a/server/szurubooru/func/comments.py b/server/szurubooru/func/comments.py
index 8ea06e3d..f6e18e97 100644
--- a/server/szurubooru/func/comments.py
+++ b/server/szurubooru/func/comments.py
@@ -5,7 +5,7 @@ from szurubooru.func import users, scores, util
 class CommentNotFoundError(errors.NotFoundError): pass
 class EmptyCommentTextError(errors.ValidationError): pass
 
-def serialize_comment(comment, authenticated_user):
+def serialize_comment(comment, authenticated_user, options=None):
     return util.serialize_entity(
         comment,
         {
@@ -16,7 +16,8 @@ def serialize_comment(comment, authenticated_user):
             'creationTime': lambda: comment.creation_time,
             'lastEditTime': lambda: comment.last_edit_time,
             'ownScore': lambda: scores.get_score(comment, authenticated_user),
-        })
+        },
+        options)
 
 def try_get_comment_by_id(comment_id):
     return db.session \
diff --git a/server/szurubooru/func/posts.py b/server/szurubooru/func/posts.py
index 08859b86..99ff36d2 100644
--- a/server/szurubooru/func/posts.py
+++ b/server/szurubooru/func/posts.py
@@ -61,7 +61,7 @@ def serialize_note(note):
         'text': note.text,
     }
 
-def serialize_post(post, authenticated_user):
+def serialize_post(post, authenticated_user, options=None):
     return util.serialize_entity(
         post,
         {
@@ -98,7 +98,8 @@ def serialize_post(post, authenticated_user):
                 comments.serialize_comment(comment, authenticated_user) \
                     for comment in post.comments],
             'snapshots': lambda: snapshots.get_serialized_history(post),
-        })
+        },
+        options)
 
 def get_post_count():
     return db.session.query(sqlalchemy.func.count(db.Post.post_id)).one()[0]
diff --git a/server/szurubooru/func/tag_categories.py b/server/szurubooru/func/tag_categories.py
index 6d3f8f79..5e91c481 100644
--- a/server/szurubooru/func/tag_categories.py
+++ b/server/szurubooru/func/tag_categories.py
@@ -14,7 +14,7 @@ def _verify_name_validity(name):
         raise InvalidTagCategoryNameError(
             'Name must satisfy regex %r.' % name_regex)
 
-def serialize_category(category):
+def serialize_category(category, options=None):
     return util.serialize_entity(
         category,
         {
@@ -23,7 +23,8 @@ def serialize_category(category):
             'usages': lambda: category.tag_count,
             'default': lambda: category.default,
             'snapshots': lambda: snapshots.get_serialized_history(category),
-        })
+        },
+        options)
 
 def create_category(name, color):
     category = db.TagCategory()
diff --git a/server/szurubooru/func/tags.py b/server/szurubooru/func/tags.py
index 9f07cddd..057fa18e 100644
--- a/server/szurubooru/func/tags.py
+++ b/server/szurubooru/func/tags.py
@@ -36,7 +36,7 @@ def _get_default_category_name():
     else:
         return DEFAULT_CATEGORY_NAME
 
-def serialize_tag(tag):
+def serialize_tag(tag, options=None):
     return util.serialize_entity(
         tag,
         {
@@ -50,7 +50,8 @@ def serialize_tag(tag):
             'implications': lambda: [
                 relation.names[0].name for relation in tag.implications],
             'snapshots': lambda: snapshots.get_serialized_history(tag),
-        })
+        },
+        options)
 
 def export_to_json():
     output = {
diff --git a/server/szurubooru/func/users.py b/server/szurubooru/func/users.py
index 128e6264..d2f46c52 100644
--- a/server/szurubooru/func/users.py
+++ b/server/szurubooru/func/users.py
@@ -28,7 +28,7 @@ def _get_email(user, authenticated_user, force_show_email):
         return False
     return user.email
 
-def serialize_user(user, authenticated_user, force_show_email=False):
+def serialize_user(user, authenticated_user, options=None, force_show_email=False):
     return util.serialize_entity(
         user,
         {
@@ -39,7 +39,8 @@ def serialize_user(user, authenticated_user, force_show_email=False):
             'avatarStyle': lambda: user.avatar_style,
             'avatarUrl': lambda: _get_avatar_url(user),
             'email': lambda: _get_email(user, authenticated_user, force_show_email),
-        })
+        },
+        options)
 
 def get_user_count():
     return db.session.query(db.User).count()
diff --git a/server/szurubooru/func/util.py b/server/szurubooru/func/util.py
index 3a4208a8..908c760f 100644
--- a/server/szurubooru/func/util.py
+++ b/server/szurubooru/func/util.py
@@ -6,12 +6,21 @@ import tempfile
 from contextlib import contextmanager
 from szurubooru.errors import ValidationError
 
-def serialize_entity(entity, field_factories):
+def get_serialization_options(ctx):
+    return ctx.get_param_as_list('_fields', required=False, default=None)
+
+def serialize_entity(entity, field_factories, options):
     if not entity:
         return None
+    if not options:
+        options = field_factories.keys()
     ret = {}
-    for key, factory in field_factories.items():
-        ret[key] = factory()
+    for key in options:
+        try:
+            factory = field_factories[key]
+            ret[key] = factory()
+        except KeyError:
+            pass
     return ret
 
 @contextmanager
diff --git a/server/szurubooru/tests/api/test_post_creating.py b/server/szurubooru/tests/api/test_post_creating.py
index adb0b208..a15efbc6 100644
--- a/server/szurubooru/tests/api/test_post_creating.py
+++ b/server/szurubooru/tests/api/test_post_creating.py
@@ -54,7 +54,7 @@ def test_creating_minimal_posts(
         posts.update_post_notes.assert_called_once_with(post, [])
         posts.update_post_flags.assert_called_once_with(post, [])
         posts.update_post_thumbnail.assert_called_once_with(post, 'post-thumbnail')
-        posts.serialize_post.assert_called_once_with(post, auth_user)
+        posts.serialize_post.assert_called_once_with(post, auth_user, options=None)
         tags.export_to_json.assert_called_once_with()
         snapshots.save_entity_creation.assert_called_once_with(post, auth_user)
 
@@ -100,7 +100,7 @@ def test_creating_full_posts(context_factory, post_factory, user_factory):
         posts.update_post_relations.assert_called_once_with(post, [1, 2])
         posts.update_post_notes.assert_called_once_with(post, ['note1', 'note2'])
         posts.update_post_flags.assert_called_once_with(post, ['flag1', 'flag2'])
-        posts.serialize_post.assert_called_once_with(post, auth_user)
+        posts.serialize_post.assert_called_once_with(post, auth_user, options=None)
         tags.export_to_json.assert_called_once_with()
         snapshots.save_entity_creation.assert_called_once_with(post, auth_user)
 
diff --git a/server/szurubooru/tests/api/test_post_updating.py b/server/szurubooru/tests/api/test_post_updating.py
index fc14c275..f2852652 100644
--- a/server/szurubooru/tests/api/test_post_updating.py
+++ b/server/szurubooru/tests/api/test_post_updating.py
@@ -67,7 +67,7 @@ def test_post_updating(
         posts.update_post_relations.assert_called_once_with(post, [1, 2])
         posts.update_post_notes.assert_called_once_with(post, ['note1', 'note2'])
         posts.update_post_flags.assert_called_once_with(post, ['flag1', 'flag2'])
-        posts.serialize_post.assert_called_once_with(post, auth_user)
+        posts.serialize_post.assert_called_once_with(post, auth_user, options=None)
         tags.export_to_json.assert_called_once_with()
         snapshots.save_entity_modification.assert_called_once_with(post, auth_user)
         assert post.last_edit_time == datetime.datetime(1997, 1, 1)