diff --git a/README.rst b/README.rst
index 88b9c619..57d6b23b 100644
--- a/README.rst
+++ b/README.rst
@@ -5,10 +5,18 @@ audbackend
 |tests| |coverage| |docs| |python-versions| |license|
 
 Manage file storage on different backends.
-At the moment we support:
 
-* Artifactory_ with ``audbackend.Artifactory``
-* local file system with ``audbackend.FileSystem``
+At the moment we support
+the following backends:
+
+* Artifactory_ with ``audbackend.backend.Artifactory``
+* local file system with ``audbackend.backend.FileSystem``
+
+And the following interfaces
+to access files on a backend:
+
+* unversioned with ``audbackend.interface.Unversioned``
+* versioned with  ``audbackend.interface.Versioned``
 
 Have a look at the installation_ instructions.
 
diff --git a/audbackend/__init__.py b/audbackend/__init__.py
index da645b15..5b2d7266 100644
--- a/audbackend/__init__.py
+++ b/audbackend/__init__.py
@@ -1,17 +1,18 @@
+from audbackend import backend
 from audbackend import interface
 from audbackend.core.api import access
 from audbackend.core.api import available
 from audbackend.core.api import create
 from audbackend.core.api import delete
 from audbackend.core.api import register
-from audbackend.core.backend import Backend
+from audbackend.core.backend.base import Base as Backend  # legacy
+from audbackend.core.backend.filesystem import FileSystem  # legacy
 from audbackend.core.errors import BackendError
-from audbackend.core.filesystem import FileSystem
 from audbackend.core.repository import Repository
 
-# Import optional backends
+# Import optional backends (legacy)
 try:
-    from audbackend.core.artifactory import Artifactory
+    from audbackend.core.backend.artifactory import Artifactory
 except ImportError:  # pragma: no cover
     pass
 
diff --git a/audbackend/backend/__init__.py b/audbackend/backend/__init__.py
new file mode 100644
index 00000000..06be3a6a
--- /dev/null
+++ b/audbackend/backend/__init__.py
@@ -0,0 +1,8 @@
+from audbackend.core.backend.base import Base
+from audbackend.core.backend.filesystem import FileSystem
+
+# Import optional backends
+try:
+    from audbackend.core.backend.artifactory import Artifactory
+except ImportError:  # pragma: no cover
+    pass
diff --git a/audbackend/core/api.py b/audbackend/core/api.py
index 75c708e1..490c7e77 100644
--- a/audbackend/core/api.py
+++ b/audbackend/core/api.py
@@ -1,8 +1,8 @@
 import typing
 
 from audbackend.core import utils
-from audbackend.core.backend import Backend
-from audbackend.core.filesystem import FileSystem
+from audbackend.core.backend.base import Base
+from audbackend.core.backend.filesystem import FileSystem
 from audbackend.core.interface.base import Base as Interface
 from audbackend.core.interface.versioned import Versioned
 
@@ -18,7 +18,7 @@ def _backend(
         name: str,
         host: str,
         repository: str,
-) -> Backend:
+) -> Base:
     r"""Get backend instance."""
     if name not in backend_registry:
         raise ValueError(
@@ -89,7 +89,7 @@ def access(
 
     Examples:
         >>> access('file-system', 'host', 'repo')
-        audbackend.core.interface.versioned.Versioned('audbackend.core.filesystem.FileSystem', 'host', 'repo')
+        audbackend.core.interface.versioned.Versioned('audbackend.core.backend.filesystem.FileSystem', 'host', 'repo')
 
     """  # noqa: E501
     backend = _backend(name, host, repository)
@@ -98,7 +98,7 @@ def access(
     return interface(backend, **interface_kwargs)
 
 
-def available() -> typing.Dict[str, typing.List[Backend]]:
+def available() -> typing.Dict[str, typing.List[Base]]:
     r"""List available backend instances.
 
     Returns a dictionary with
@@ -114,7 +114,7 @@ def available() -> typing.Dict[str, typing.List[Backend]]:
         >>> list(available())
         ['artifactory', 'file-system']
         >>> available()['file-system'][0]
-        ('audbackend.core.filesystem.FileSystem', 'host', 'repo')
+        ('audbackend.core.backend.filesystem.FileSystem', 'host', 'repo')
 
     """  # noqa: E501
     result = {}
@@ -174,7 +174,7 @@ def create(
 
     Examples:
         >>> create('file-system', 'host', 'repository')
-        audbackend.core.interface.versioned.Versioned('audbackend.core.filesystem.FileSystem', 'host', 'repository')
+        audbackend.core.interface.versioned.Versioned('audbackend.core.backend.filesystem.FileSystem', 'host', 'repository')
 
     """  # noqa: E501
     backend = _backend(name, host, repository)
@@ -222,7 +222,7 @@ def delete(
 
 def register(
         name: str,
-        cls: typing.Type[Backend],
+        cls: typing.Type[Base],
 ):
     r"""Register backend class.
 
@@ -245,7 +245,7 @@ def register(
 
 # Register optional backends
 try:
-    from audbackend.core.artifactory import Artifactory
+    from audbackend.core.backend.artifactory import Artifactory
     register('artifactory', Artifactory)
 except ImportError:  # pragma: no cover
     pass
diff --git a/audbackend/core/backend/__init__.py b/audbackend/core/backend/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/audbackend/core/artifactory.py b/audbackend/core/backend/artifactory.py
similarity index 99%
rename from audbackend/core/artifactory.py
rename to audbackend/core/backend/artifactory.py
index a9f9163d..910d39d4 100644
--- a/audbackend/core/artifactory.py
+++ b/audbackend/core/backend/artifactory.py
@@ -7,7 +7,7 @@
 import audeer
 
 from audbackend.core import utils
-from audbackend.core.backend import Backend
+from audbackend.core.backend.base import Base
 
 
 def _artifactory_path(
@@ -110,7 +110,7 @@ def _download(
                         pbar.update(n_data)
 
 
-class Artifactory(Backend):
+class Artifactory(Base):
     r"""Backend for Artifactory.
 
     Looks for the two environment variables
diff --git a/audbackend/core/backend.py b/audbackend/core/backend/base.py
similarity index 99%
rename from audbackend/core/backend.py
rename to audbackend/core/backend/base.py
index 0d5684ba..85f15aec 100644
--- a/audbackend/core/backend.py
+++ b/audbackend/core/backend/base.py
@@ -9,7 +9,7 @@
 from audbackend.core.errors import BackendError
 
 
-class Backend:
+class Base:
     r"""Backend base class.
 
     Derive from this class to implement a new backend.
diff --git a/audbackend/core/filesystem.py b/audbackend/core/backend/filesystem.py
similarity index 98%
rename from audbackend/core/filesystem.py
rename to audbackend/core/backend/filesystem.py
index 7f5f3ba2..5741af02 100644
--- a/audbackend/core/filesystem.py
+++ b/audbackend/core/backend/filesystem.py
@@ -6,10 +6,10 @@
 import audeer
 
 from audbackend.core import utils
-from audbackend.core.backend import Backend
+from audbackend.core.backend.base import Base
 
 
-class FileSystem(Backend):
+class FileSystem(Base):
     r"""Backend for file system.
 
     Args:
diff --git a/audbackend/core/conftest.py b/audbackend/core/conftest.py
index 6992159d..959914a1 100644
--- a/audbackend/core/conftest.py
+++ b/audbackend/core/conftest.py
@@ -9,10 +9,10 @@
 import audbackend
 
 
-class DoctestFileSystem(audbackend.FileSystem):
+class DoctestFileSystem(audbackend.backend.FileSystem):
 
     def __repr__(self) -> str:
-        name = 'audbackend.core.filesystem.FileSystem'
+        name = 'audbackend.core.backend.filesystem.FileSystem'
         return str((name, self.host, self.repository))
 
     def _date(
@@ -45,7 +45,7 @@ def prepare_docstring_tests(doctest_namespace):
 
         # backend
 
-        backend = audbackend.Backend('host', 'repo')
+        backend = audbackend.backend.Base('host', 'repo')
         doctest_namespace['backend'] = backend
 
         interface = audbackend.interface.Base(backend)
@@ -84,6 +84,6 @@ def prepare_docstring_tests(doctest_namespace):
 
         audbackend.delete('file-system', 'host', 'repo')
         audbackend.delete('file-system', 'host', 'repo-unversioned')
-        audbackend.register('file-system', audbackend.FileSystem)
+        audbackend.register('file-system', audbackend.backend.FileSystem)
 
         os.chdir(current_dir)
diff --git a/audbackend/core/interface/__init__.py b/audbackend/core/interface/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/audbackend/core/interface/base.py b/audbackend/core/interface/base.py
index 657cf90f..1e3315c6 100644
--- a/audbackend/core/interface/base.py
+++ b/audbackend/core/interface/base.py
@@ -1,6 +1,6 @@
 import typing
 
-from audbackend.core.backend import Backend
+from audbackend.core.backend.base import Base as Backend
 
 
 class Base:
@@ -38,7 +38,7 @@ def backend(self) -> Backend:
 
         Examples:
             >>> interface.backend
-            ('audbackend.core.backend.Backend', 'host', 'repo')
+            ('audbackend.core.backend.base.Base', 'host', 'repo')
 
         """
         return self._backend
diff --git a/audbackend/core/interface/versioned.py b/audbackend/core/interface/versioned.py
index c10b5747..907400f5 100644
--- a/audbackend/core/interface/versioned.py
+++ b/audbackend/core/interface/versioned.py
@@ -5,7 +5,6 @@
 import audeer
 
 from audbackend.core import utils
-from audbackend.core.backend import Backend
 from audbackend.core.errors import BackendError
 from audbackend.core.interface.base import Base
 
@@ -20,7 +19,7 @@ class Versioned(Base):
 
     def __init__(
             self,
-            backend: Backend,
+            backend: Base,
     ):
         super().__init__(backend)
 
diff --git a/docs/api-src/audbackend.backend.rst b/docs/api-src/audbackend.backend.rst
new file mode 100644
index 00000000..8ddd01b0
--- /dev/null
+++ b/docs/api-src/audbackend.backend.rst
@@ -0,0 +1,24 @@
+audbackend.backend
+==================
+
+.. automodule:: audbackend.backend
+
+Currently the following
+backends are supported:
+
+.. autosummary::
+    :toctree:
+    :nosignatures:
+
+    Artifactory
+    FileSystem
+
+Users can implement their own
+backend by deriving from
+:class:`audbackend.backend.Base`.
+
+.. autosummary::
+    :toctree:
+    :nosignatures:
+
+    Base
diff --git a/docs/api-src/audbackend.interface.rst b/docs/api-src/audbackend.interface.rst
index b59e74ed..5df85253 100644
--- a/docs/api-src/audbackend.interface.rst
+++ b/docs/api-src/audbackend.interface.rst
@@ -4,10 +4,7 @@ audbackend.interface
 .. automodule:: audbackend.interface
 
 To access the files on a backend users
-can choose between two interfaces
-:class:`audbackend.interface.Unversioned`
-or
-:class:`audbackend.interface.Versioned`:
+can use the following interfaces:
 
 .. autosummary::
     :toctree:
diff --git a/docs/api-src/audbackend.rst b/docs/api-src/audbackend.rst
index cc942d50..f9705094 100644
--- a/docs/api-src/audbackend.rst
+++ b/docs/api-src/audbackend.rst
@@ -3,32 +3,26 @@ audbackend
 
 .. automodule:: audbackend
 
-A backend is a generic interface
+:mod:`audbackend`
+provides an abstract layer
 for storing and accessing files
 on a host.
 
-Currently the following backends
-are shipped with :mod:`audbackend`:
+This involves two components:
 
-.. autosummary::
-    :toctree:
-    :nosignatures:
-
-    Artifactory
-    FileSystem
-
-Users can implement their own
-backend by deriving from
-:class:`audbackend.Backend`.
-
-.. autosummary::
-    :toctree:
-    :nosignatures:
+1. A *backend* that
+   implements file operations
+   on a specific storing device
+   (:mod:`audbackend.backend`).
 
-    Backend
+2. An *interface* that
+   passes user requests
+   to a backend
+   (:mod:`audbackend.interface`).
 
-In addition to the backends
-the following classes and functions are available.
+Additionally,
+the following classes
+and functions are available.
 
 .. autosummary::
     :toctree:
diff --git a/docs/index.rst b/docs/index.rst
index 9070cdaf..b520c79a 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -16,6 +16,7 @@
     :hidden:
 
     api/audbackend
+    api/audbackend.backend
     api/audbackend.interface
     genindex
 
diff --git a/docs/install.rst b/docs/install.rst
index 32562d46..d0911b32 100644
--- a/docs/install.rst
+++ b/docs/install.rst
@@ -11,7 +11,8 @@ To install :mod:`audbackend` run:
     $ pip install audbackend
 
 By default,
-only the :class:`audbackend.FileSystem` backend will be installed.
+only the :class:`audbackend.backend.FileSystem`
+backend will be installed.
 To install all backends run:
 
 .. code-block:: bash
@@ -19,7 +20,7 @@ To install all backends run:
     $ pip install audbackend[all]
 
 or select single backends,
-e.g. :class:`audbackend.Artifactory`
+e.g. :class:`audbackend.backend.Artifactory`
 
 .. code-block:: bash
 
diff --git a/docs/usage.rst b/docs/usage.rst
index 8f85dda5..3a5addee 100644
--- a/docs/usage.rst
+++ b/docs/usage.rst
@@ -42,17 +42,10 @@ a SQLite_ database.
 File-system example
 -------------------
 
-The heart of
-:mod:`audbackend`
-is the class
-:class:`audbackend.Backend`,
-which provides an abstract
-interface to communicate
-with a storage system.
 The class
-:class:`audbackend.FileSystem`
+:class:`audbackend.backend.FileSystem`
 implements
-:class:`audbackend.Backend`
+:class:`audbackend.backend.Base`
 for a standard file system.
 
 
@@ -67,7 +60,7 @@ if we do it again).
 
     import audbackend
 
-    audbackend.register('file-system', audbackend.FileSystem)
+    audbackend.register('file-system', audbackend.backend.FileSystem)
 
 
 To make sure we can keep track
@@ -199,8 +192,8 @@ on the backend.
 
 When we get an archive from the backend
 we can automatically extract it,
-by using :meth:`audbackend.FileSystem.get_archive`
-instead of :meth:`audbackend.FileSystem.get_file`.
+by using :meth:`audbackend.backend.FileSystem.get_archive`
+instead of :meth:`audbackend.backend.FileSystem.get_file`.
 
 .. jupyter-execute::
 
@@ -349,7 +342,7 @@ helper class.
         and write changes back to the backend.
 
         """
-        def __init__(self, backend: audbackend.Backend):
+        def __init__(self, backend: audbackend.backend.Base):
             self.backend = backend
 
         def __enter__(self) -> shelve.Shelf:
@@ -420,7 +413,7 @@ a SQLite_ database.
 A new backend
 should be implemented as a class
 deriving from
-:class:`audbackend.Backend`.
+:class:`audbackend.backend.Base`.
 As can be seen in the file
 :file:`audbackend/core/backend.py`,
 we need to implement the following private methods:
@@ -451,7 +444,7 @@ in the constructor:
     import audbackend
     import os
 
-    class SQLite(audbackend.Backend):
+    class SQLite(audbackend.backend.Base):
 
         def __init__(
                 self,
diff --git a/tests/conftest.py b/tests/conftest.py
index 69c9d398..87861d9d 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -10,7 +10,7 @@
 import audbackend
 
 
-# list of backends that will be tested by default
+# list of backends to test
 pytest.BACKENDS = [
     'artifactory',
     'file-system',
@@ -19,12 +19,13 @@
     pytest.BACKENDS.append('single-folder')
 
 
+# list of interfaces to test
 pytest.UNVERSIONED = [
     (backend, audbackend.interface.Unversioned)
     for backend in pytest.BACKENDS
 ]
 pytest.VERSIONED = [
-    ('file-system', audbackend.interface.Versioned)
+    ('file-system', audbackend.interface.Versioned),
 ]
 
 # UID for test session
@@ -53,7 +54,7 @@ def owner(request):
     r"""Return expected owner value."""
     name = request.param
     if name == 'artifactory':
-        owner = audbackend.core.artifactory._authentication(
+        owner = audbackend.core.backend.artifactory._authentication(
             'audeering.jfrog.io/artifactory'
         )[0]
     else:
diff --git a/tests/singlefolder.py b/tests/singlefolder.py
index a85ae0d2..c9354458 100644
--- a/tests/singlefolder.py
+++ b/tests/singlefolder.py
@@ -10,7 +10,7 @@
 import audbackend
 
 
-class SingleFolder(audbackend.Backend):
+class SingleFolder(audbackend.backend.Base):
     r"""Backend implemented in a single folder.
 
     Files put on the backend
diff --git a/tests/test_api.py b/tests/test_api.py
index 986d3edd..38da83f2 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -12,13 +12,13 @@
             'file-system',
             'file-system',
             f'unittest-{audeer.uid()[:8]}',
-            audbackend.FileSystem,
+            audbackend.backend.FileSystem,
         ),
         (
             'artifactory',
             'artifactory',
             f'unittest-{audeer.uid()[:8]}',
-            audbackend.Artifactory,
+            audbackend.backend.Artifactory,
         ),
         pytest.param(  # backend does not exist
             'bad-backend',
diff --git a/tests/test_backend_artifactory.py b/tests/test_backend_artifactory.py
index 863adb7e..5497b66b 100644
--- a/tests/test_backend_artifactory.py
+++ b/tests/test_backend_artifactory.py
@@ -41,14 +41,14 @@ def test_authentication(tmpdir, hosts, hide_credentials):
 
     # config file does not exist
 
-    backend = audbackend.Artifactory(host, 'repository')
+    backend = audbackend.backend.Artifactory(host, 'repository')
     assert backend._username == 'anonymous'
     assert backend._api_key == ''
 
     # config file is empty
 
     audeer.touch(config_path)
-    backend = audbackend.Artifactory(host, 'repository')
+    backend = audbackend.backend.Artifactory(host, 'repository')
     assert backend._username == 'anonymous'
     assert backend._api_key == ''
 
@@ -57,7 +57,7 @@ def test_authentication(tmpdir, hosts, hide_credentials):
     with open(config_path, 'w') as fp:
         fp.write(f'[{host}]\n')
 
-    backend = audbackend.Artifactory(host, 'repository')
+    backend = audbackend.backend.Artifactory(host, 'repository')
     assert backend._username == 'anonymous'
     assert backend._api_key == ''
 
@@ -71,7 +71,7 @@ def test_authentication(tmpdir, hosts, hide_credentials):
         fp.write(f'password = {api_key}\n')
 
     with pytest.raises(dohq_artifactory.exception.ArtifactoryException):
-        audbackend.Artifactory(host, 'repository')
+        audbackend.backend.Artifactory(host, 'repository')
 
 
 @pytest.mark.parametrize(
diff --git a/tests/test_backend_base.py b/tests/test_backend_base.py
index 1157ffbe..f8ee6422 100644
--- a/tests/test_backend_base.py
+++ b/tests/test_backend_base.py
@@ -40,7 +40,7 @@
 @pytest.mark.parametrize(
     'backend',
     [
-        audbackend.Backend('host', 'repository'),
+        audbackend.backend.Base('host', 'repository'),
     ]
 )
 def test_join(paths, expected, backend):
@@ -76,7 +76,7 @@ def test_join(paths, expected, backend):
 @pytest.mark.parametrize(
     'backend',
     [
-        audbackend.Backend('host', 'repository'),
+        audbackend.backend.Base('host', 'repository'),
     ]
 )
 def test_split(path, expected, backend):
diff --git a/tests/test_backend_filesystem.py b/tests/test_backend_filesystem.py
index d0097b79..17b7cd9a 100644
--- a/tests/test_backend_filesystem.py
+++ b/tests/test_backend_filesystem.py
@@ -7,7 +7,7 @@
 import audbackend
 
 
-class BadFileSystem(audbackend.FileSystem):
+class BadFileSystem(audbackend.backend.FileSystem):
     r"""Imitates a corrupted file system."""
     def _get_file(
             self,
@@ -24,7 +24,7 @@ def _get_file(
 def bad_file_system():
     audbackend.register('file-system', BadFileSystem)
     yield
-    audbackend.register('file-system', audbackend.FileSystem)
+    audbackend.register('file-system', audbackend.backend.FileSystem)
 
 
 @pytest.mark.parametrize(
diff --git a/tests/test_backend_filesystem_only.py b/tests/test_backend_filesystem_only.py
index 12617250..23db6719 100644
--- a/tests/test_backend_filesystem_only.py
+++ b/tests/test_backend_filesystem_only.py
@@ -5,4 +5,4 @@
 
 # Check optional backends are not available
 with pytest.raises(AttributeError):
-    audbackend.Artifactory('https://host.com', 'repo')
+    audbackend.backend.Artifactory('https://host.com', 'repo')
diff --git a/tests/test_legacy_import.py b/tests/test_legacy_import.py
new file mode 100644
index 00000000..c3a09453
--- /dev/null
+++ b/tests/test_legacy_import.py
@@ -0,0 +1,8 @@
+import audbackend
+
+
+def test_legacy_import(hosts):
+
+    audbackend.Backend('host', 'repo')
+    audbackend.Artifactory(hosts['artifactory'], 'repo')
+    audbackend.FileSystem(hosts['file-system'], 'repo')