diff --git a/.git-blame-ignore-revs b/.git-blame-ignore-revs
new file mode 100644
index 0000000000..858d673868
--- /dev/null
+++ b/.git-blame-ignore-revs
@@ -0,0 +1 @@
+# Initial pre-commit reformat
diff --git a/.gitconfig b/.gitconfig
new file mode 100644
index 0000000000..0559a09e0c
--- /dev/null
+++ b/.gitconfig
@@ -0,0 +1,2 @@
+[blame]
+    ignoreRevsFile = .git-blame-ignore-revs
diff --git a/.github/workflows/python-linux.yml b/.github/workflows/python-linux.yml
index b57ecf0463..81bc8d7bff 100644
--- a/.github/workflows/python-linux.yml
+++ b/.github/workflows/python-linux.yml
@@ -5,6 +5,30 @@ on:
   pull_request:
     branches: '*'
 jobs:
+  # Run "pre-commit run --all-files"
+  pre-commit:
+    runs-on: ubuntu-20.04
+    timeout-minutes: 2
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+        with:
+          python-version: 3.8
+
+      # ref: https://github.com/pre-commit/action
+      - uses: pre-commit/action@v2.0.0
+      - name: Help message if pre-commit fail
+        if: ${{ failure() }}
+        run: |
+          echo "You can install pre-commit hooks to automatically run formatting"
+          echo "on each commit with:"
+          echo "    pre-commit install"
+          echo "or you can run by hand on staged files with"
+          echo "    pre-commit run"
+          echo "or after-the-fact on already committed files with"
+          echo "    pre-commit run --all-files"
+
   build:
     runs-on: ${{ matrix.os }}-latest
     strategy:
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000000..32bd0e3f42
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,34 @@
+repos:
+  - repo: https://github.com/asottile/reorder_python_imports
+    rev: v1.9.0
+    hooks:
+      - id: reorder-python-imports
+  - repo: https://github.com/psf/black
+    rev: 20.8b1
+    hooks:
+      - id: black
+        args: ["--line-length", "100"]
+  - repo: https://github.com/pre-commit/mirrors-prettier
+    rev: v2.2.1
+    hooks:
+      - id: prettier
+  - repo: https://gitlab.com/pycqa/flake8
+    rev: "3.8.4"
+    hooks:
+      - id: flake8
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v3.4.0
+    hooks:
+      - id: end-of-file-fixer
+      - id: check-case-conflict
+      - id: check-executables-have-shebangs
+      - id: requirements-txt-fixer
+  - repo: https://github.com/pre-commit/mirrors-eslint
+    rev: v7.32.0
+    hooks:
+      - id: eslint
+  - repo: https://github.com/pre-commit/mirrors-pylint
+    rev: v3.0.0a3
+    hooks:
+      - id: pylint
+        args: [--disable=all, --enable=unused-import]
diff --git a/.prettierignore b/.prettierignore
new file mode 100644
index 0000000000..b0e34edeb4
--- /dev/null
+++ b/.prettierignore
@@ -0,0 +1 @@
+**/templates/*.html
diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index c58a0d446d..b25be508d9 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -37,6 +37,33 @@ from any directory in your system with::
 
     jupyter server
 
+
+Code Styling
+-----------------------------
+`jupyter_server` has adopted automatic code formatting so you shouldn't
+need to worry too much about your code style.
+As long as your code is valid,
+the pre-commit hook should take care of how it should look.
+To install `pre-commit`, run the following::
+
+    pip install pre-commit
+    pre-commit install
+
+
+You can invoke the pre-commit hook by hand at any time with::
+
+    pre-commit run
+
+which should run any autoformatting on your code
+and tell you about any errors it couldn't fix automatically.
+You may also install [black integration](https://github.com/psf/black#editor-integration)
+into your text editor to format code automatically.
+
+If you have already committed files before setting up the pre-commit
+hook with ``pre-commit install``, you can fix everything up using
+``pre-commit run --all-files``. You need to make the fixing commit
+yourself after that.
+
 Troubleshooting the Installation
 --------------------------------
 
diff --git a/docs/source/conf.py b/docs/source/conf.py
index 79f9df3ed6..b9be17d3eb 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -16,7 +16,6 @@
 import sys
 import os
 import os.path as osp
-import shlex
 import shutil
 
 HERE = osp.abspath(osp.dirname(__file__))
@@ -378,7 +377,7 @@
 spelling_word_list_filename='spelling_wordlist.txt'
 
 # import before any doc is built, so _ is guaranteed to be injected
-import jupyter_server.transutils
+import jupyter_server.transutils  # pylint: disable=unused-import
 
 
 def setup(app):
diff --git a/examples/simple/setup.py b/examples/simple/setup.py
old mode 100755
new mode 100644
diff --git a/examples/simple/simple_ext1/application.py b/examples/simple/simple_ext1/application.py
index 4ddf889096..3cf9211ad7 100644
--- a/examples/simple/simple_ext1/application.py
+++ b/examples/simple/simple_ext1/application.py
@@ -1,4 +1,4 @@
-import os, jinja2
+import os
 from traitlets import Unicode
 from jupyter_server.extension.application import ExtensionApp, ExtensionAppJinjaMixin
 from .handlers import (DefaultHandler, RedirectHandler,
diff --git a/examples/simple/simple_ext1/handlers.py b/examples/simple/simple_ext1/handlers.py
index 77b2903b64..c3765edeca 100644
--- a/examples/simple/simple_ext1/handlers.py
+++ b/examples/simple/simple_ext1/handlers.py
@@ -7,7 +7,7 @@ def get(self):
         # The name of the extension to which this handler is linked.
         self.log.info("Extension Name in {} Default Handler: {}".format(self.name, self.name))
         # A method for getting the url to static files (prefixed with /static/<name>).
-        self.log.info("Static URL for / in simple_ext1 Default Handler:".format(self.static_url(path='/')))
+        self.log.info("Static URL for / in simple_ext1 Default Handler: {}".format(self.static_url(path='/')))
         self.write('<h1>Hello Simple 1 - I am the default...</h1>')
         self.write('Config in {} Default Handler: {}'.format(self.name, self.config))
 
diff --git a/examples/simple/simple_ext2/application.py b/examples/simple/simple_ext2/application.py
index be59ce9bfa..d485265691 100644
--- a/examples/simple/simple_ext2/application.py
+++ b/examples/simple/simple_ext2/application.py
@@ -1,4 +1,4 @@
-import os, jinja2
+import os
 from traitlets import Unicode
 from jupyter_server.extension.application import ExtensionApp, ExtensionAppJinjaMixin
 from .handlers import ParameterHandler, TemplateHandler, IndexHandler, ErrorHandler
diff --git a/jupyter_server/_sysinfo.py b/jupyter_server/_sysinfo.py
index ae0999fe9e..6e57102567 100644
--- a/jupyter_server/_sysinfo.py
+++ b/jupyter_server/_sysinfo.py
@@ -8,11 +8,10 @@
 
 import os
 import platform
-import pprint
 import sys
 import subprocess
 
-from ipython_genutils import py3compat, encoding
+from ipython_genutils import encoding
 
 import jupyter_server
 
diff --git a/jupyter_server/base/handlers.py b/jupyter_server/base/handlers.py
old mode 100755
new mode 100644
index 3d1a336301..6877ea7284
--- a/jupyter_server/base/handlers.py
+++ b/jupyter_server/base/handlers.py
@@ -10,7 +10,6 @@
 import mimetypes
 import os
 import re
-import sys
 import traceback
 import types
 import warnings
@@ -18,7 +17,7 @@
 from http.cookies import Morsel
 from urllib.parse import urlparse
 from jinja2 import TemplateNotFound
-from tornado import web, gen, escape, httputil
+from tornado import web, escape, httputil
 from tornado.log import app_log
 import prometheus_client
 
diff --git a/jupyter_server/extension/manager.py b/jupyter_server/extension/manager.py
index 83f1af7943..f9dcc2e8b6 100644
--- a/jupyter_server/extension/manager.py
+++ b/jupyter_server/extension/manager.py
@@ -15,7 +15,7 @@
     Instance,
     default,
     observe,
-    validate,
+    validate as validate_trait,
 )
 
 from .config import ExtensionConfigManager
@@ -36,7 +36,7 @@ class ExtensionPoint(HasTraits):
 
     metadata = Dict()
 
-    @validate('metadata')
+    @validate_trait('metadata')
     def _valid_metadata(self, proposed):
         metadata = proposed['value']
         # Verify that the metadata has a "name" key.
@@ -180,7 +180,7 @@ def __init__(self, *args, **kwargs):
 
     _linked_points = {}
 
-    @validate("name")
+    @validate_trait("name")
     def _validate_name(self, proposed):
         name = proposed['value']
         self._extension_points = {}
diff --git a/jupyter_server/nbconvert/handlers.py b/jupyter_server/nbconvert/handlers.py
index b9cb711a68..85a48f9af6 100644
--- a/jupyter_server/nbconvert/handlers.py
+++ b/jupyter_server/nbconvert/handlers.py
@@ -7,7 +7,7 @@
 import os
 import zipfile
 
-from tornado import web, escape
+from tornado import web
 from tornado.log import app_log
 
 from ..base.handlers import (
diff --git a/jupyter_server/prometheus/metrics.py b/jupyter_server/prometheus/metrics.py
index 71192b4eaf..3ebe4d074d 100644
--- a/jupyter_server/prometheus/metrics.py
+++ b/jupyter_server/prometheus/metrics.py
@@ -9,7 +9,8 @@
     # Jupyter Notebook also defines these metrics.  Re-defining them results in a ValueError.
     # Try to de-duplicate by using the ones in Notebook if available.
     # See https://github.com/jupyter/jupyter_server/issues/209
-    from notebook.prometheus.metrics import HTTP_REQUEST_DURATION_SECONDS, TERMINAL_CURRENTLY_RUNNING_TOTAL, KERNEL_CURRENTLY_RUNNING_TOTAL
+    # pylint: disable=unused-import
+    from notebook.prometheus.metrics import HTTP_REQUEST_DURATION_SECONDS,TERMINAL_CURRENTLY_RUNNING_TOTAL, KERNEL_CURRENTLY_RUNNING_TOTAL
 
 except ImportError:
 
diff --git a/jupyter_server/serverapp.py b/jupyter_server/serverapp.py
old mode 100755
new mode 100644
index 129e83baed..33fc4256ed
--- a/jupyter_server/serverapp.py
+++ b/jupyter_server/serverapp.py
@@ -23,10 +23,8 @@
 import socket
 import stat
 import sys
-import tempfile
 import threading
 import time
-import warnings
 import webbrowser
 import urllib
 import inspect
@@ -43,7 +41,7 @@
 
 from jupyter_core.paths import secure_write
 from jupyter_server.transutils import trans, _i18n
-from jupyter_server.utils import run_sync_in_loop
+from jupyter_server.utils import run_sync_in_loop, urljoin, pathname2url
 
 # the minimum viable tornado version: needs to be kept in sync with setup.py
 MIN_TORNADO = (6, 1, 0)
@@ -93,22 +91,21 @@
 )
 from jupyter_core.paths import jupyter_config_path
 from jupyter_client import KernelManager
-from jupyter_client.kernelspec import KernelSpecManager, NoSuchKernel, NATIVE_KERNEL_NAME
+from jupyter_client.kernelspec import KernelSpecManager
 from jupyter_client.session import Session
 from nbformat.sign import NotebookNotary
 from traitlets import (
     Any, Dict, Unicode, Integer, List, Bool, Bytes, Instance,
     TraitError, Type, Float, observe, default, validate
 )
-from jupyter_core.paths import jupyter_runtime_dir, jupyter_path
+from jupyter_core.paths import jupyter_runtime_dir
 from jupyter_server._sysinfo import get_sys_info
 
-from jupyter_server._tz import utcnow, utcfromtimestamp
+from jupyter_server._tz import utcnow
 from jupyter_server.utils import (
     url_path_join,
     check_pid,
     url_escape,
-    urljoin,
     pathname2url,
     unix_socket_in_use,
     urlencode_unix_socket_path,
diff --git a/jupyter_server/services/config/handlers.py b/jupyter_server/services/config/handlers.py
index aae6480757..245b344bf3 100644
--- a/jupyter_server/services/config/handlers.py
+++ b/jupyter_server/services/config/handlers.py
@@ -3,9 +3,6 @@
 # Copyright (c) Jupyter Development Team.
 # Distributed under the terms of the Modified BSD License.
 import json
-import os
-import io
-import errno
 from tornado import web
 
 from ...base.handlers import APIHandler
diff --git a/jupyter_server/services/contents/filemanager.py b/jupyter_server/services/contents/filemanager.py
index 1ceaaefb62..ee92155931 100644
--- a/jupyter_server/services/contents/filemanager.py
+++ b/jupyter_server/services/contents/filemanager.py
@@ -21,7 +21,7 @@
 from .manager import AsyncContentsManager, ContentsManager
 
 from ipython_genutils.importstring import import_item
-from traitlets import Any, Unicode, Bool, TraitError, observe, default, validate
+from traitlets import Any, Unicode, Bool, TraitError, default, validate
 
 from jupyter_core.paths import exists, is_hidden, is_file_hidden
 from jupyter_server import _tz as tz
diff --git a/jupyter_server/services/contents/manager.py b/jupyter_server/services/contents/manager.py
index 029966fe4b..87a13330e3 100644
--- a/jupyter_server/services/contents/manager.py
+++ b/jupyter_server/services/contents/manager.py
@@ -6,7 +6,6 @@
 from fnmatch import fnmatch
 import itertools
 import json
-import os
 import re
 
 from tornado.web import HTTPError, RequestHandler
diff --git a/jupyter_server/tests/auth/test_security.py b/jupyter_server/tests/auth/test_security.py
index ff4ea669ec..ef7943401e 100644
--- a/jupyter_server/tests/auth/test_security.py
+++ b/jupyter_server/tests/auth/test_security.py
@@ -1,4 +1,3 @@
-import pytest
 
 from jupyter_server.auth.security import passwd, passwd_check
 
diff --git a/jupyter_server/tests/extension/test_entrypoint.py b/jupyter_server/tests/extension/test_entrypoint.py
index 9a36e5117e..97af9ad17b 100644
--- a/jupyter_server/tests/extension/test_entrypoint.py
+++ b/jupyter_server/tests/extension/test_entrypoint.py
@@ -1,4 +1,3 @@
-import os
 import pytest
 
 
@@ -13,4 +12,4 @@ def test_server_extension_list(jp_environ, script_runner):
         'extension',
         'list',
     )
-    assert ret.success
\ No newline at end of file
+    assert ret.success
diff --git a/jupyter_server/tests/services/contents/test_api.py b/jupyter_server/tests/services/contents/test_api.py
index ee428c0fb9..4d91c74422 100644
--- a/jupyter_server/tests/services/contents/test_api.py
+++ b/jupyter_server/tests/services/contents/test_api.py
@@ -2,7 +2,6 @@
 import json
 import pathlib
 import pytest
-from urllib.parse import ParseResult, urlunparse
 
 import tornado
 
diff --git a/jupyter_server/tests/services/kernels/test_api.py b/jupyter_server/tests/services/kernels/test_api.py
index ddd91c8513..bfad2cef65 100644
--- a/jupyter_server/tests/services/kernels/test_api.py
+++ b/jupyter_server/tests/services/kernels/test_api.py
@@ -1,16 +1,10 @@
-import sys
 import time
 import json
 import pytest
 
-
-
 import tornado
-import urllib.parse
-from tornado.escape import url_escape
 
 from jupyter_client.kernelspec import NATIVE_KERNEL_NAME
-from jupyter_client.multikernelmanager import AsyncMultiKernelManager
 
 from jupyter_server.utils import url_path_join
 from ...utils import expected_http_error
diff --git a/jupyter_server/tests/services/kernels/test_config.py b/jupyter_server/tests/services/kernels/test_config.py
index befdd1cb19..f2761fb68c 100644
--- a/jupyter_server/tests/services/kernels/test_config.py
+++ b/jupyter_server/tests/services/kernels/test_config.py
@@ -1,4 +1,3 @@
-import sys
 import pytest
 from traitlets.config import Config
 from jupyter_server.services.kernels.kernelmanager import AsyncMappingKernelManager
diff --git a/jupyter_server/tests/services/kernels/test_cull.py b/jupyter_server/tests/services/kernels/test_cull.py
index cc58818b3b..158745cf83 100644
--- a/jupyter_server/tests/services/kernels/test_cull.py
+++ b/jupyter_server/tests/services/kernels/test_cull.py
@@ -1,8 +1,6 @@
 import asyncio
 import json
 import platform
-import sys
-import time
 import pytest
 from traitlets.config import Config
 from tornado.httpclient import HTTPClientError
diff --git a/jupyter_server/tests/test_gateway.py b/jupyter_server/tests/test_gateway.py
index 6c18bba28f..86ab2908db 100644
--- a/jupyter_server/tests/test_gateway.py
+++ b/jupyter_server/tests/test_gateway.py
@@ -7,7 +7,6 @@
 from datetime import datetime
 from tornado.web import HTTPError
 from tornado.httpclient import HTTPRequest, HTTPResponse
-from jupyter_server.serverapp import ServerApp
 from jupyter_server.gateway.managers import GatewayClient
 from jupyter_server.utils import ensure_async
 
diff --git a/jupyter_server/tests/test_serverapp.py b/jupyter_server/tests/test_serverapp.py
index a850abd067..9d4001ca4a 100644
--- a/jupyter_server/tests/test_serverapp.py
+++ b/jupyter_server/tests/test_serverapp.py
@@ -12,8 +12,7 @@
 from jupyter_server.serverapp import (
     ServerApp,
     list_running_servers,
-    JupyterPasswordApp,
-    JupyterServerStopApp
+    JupyterPasswordApp
 )
 from jupyter_server.auth.security import passwd_check
 
diff --git a/jupyter_server/tests/test_terminal.py b/jupyter_server/tests/test_terminal.py
index 7ad638d582..f11185510a 100644
--- a/jupyter_server/tests/test_terminal.py
+++ b/jupyter_server/tests/test_terminal.py
@@ -3,7 +3,6 @@
 import pytest
 import json
 import asyncio
-import sys
 
 from tornado.httpclient import HTTPClientError
 from traitlets.config import Config
diff --git a/jupyter_server/tests/unix_sockets/test_api.py b/jupyter_server/tests/unix_sockets/test_api.py
index aaa0d219e7..3d5a69ccb2 100644
--- a/jupyter_server/tests/unix_sockets/test_api.py
+++ b/jupyter_server/tests/unix_sockets/test_api.py
@@ -7,17 +7,12 @@
     reason="Unix sockets are not available on Windows."
 )
 
-import os
 import urllib
-import pathlib
 
 if not sys.platform.startswith('win'):
     from tornado.netutil import bind_unix_socket
 
-from tornado.escape import url_escape
-
 import jupyter_server.serverapp
-from jupyter_server import DEFAULT_JUPYTER_SERVER_PORT
 from jupyter_server.utils import (
     url_path_join,
     urlencode_unix_socket,
diff --git a/jupyter_server/tests/unix_sockets/test_serverapp_integration.py b/jupyter_server/tests/unix_sockets/test_serverapp_integration.py
index 6d13524a14..263de59754 100644
--- a/jupyter_server/tests/unix_sockets/test_serverapp_integration.py
+++ b/jupyter_server/tests/unix_sockets/test_serverapp_integration.py
@@ -10,7 +10,6 @@
 
 import os
 import subprocess
-import pathlib
 import time
 
 from jupyter_server.utils import urlencode_unix_socket, urlencode_unix_socket_path
@@ -164,7 +163,7 @@ def test_launch_socket_collision(jp_unix_socket_file):
     except Exception as ex:
         raise AssertionError(f"expected 'already in use' error, got '{ex}'!")
     else:
-        raise AssertionError(f"expected 'already in use' error, got success instead!")
+        raise AssertionError("expected 'already in use' error, got success instead!")
 
     # Stop the background server, ensure it's stopped and wait on the process to exit.
     subprocess.check_call(['jupyter-server', 'stop', sock])
diff --git a/jupyter_server/traittypes.py b/jupyter_server/traittypes.py
index 9f31232197..40c67be2e1 100644
--- a/jupyter_server/traittypes.py
+++ b/jupyter_server/traittypes.py
@@ -1,5 +1,6 @@
+from ast import literal_eval
 import inspect
-from traitlets import ClassBasedTraitType, Undefined, warn
+from traitlets import ClassBasedTraitType, Undefined, TraitError
 
 # Traitlet's 5.x includes a set of utilities for building
 # description strings for objects. Traitlets 5.x does not
@@ -10,7 +11,6 @@
 try:
     from traitlets.utils.descriptions import describe
 except ImportError:
-    import inspect
     import re
     import types
 
@@ -139,6 +139,17 @@ def add_article(name, definite=False, capital=False):
         else:
             return result
 
+    def _prefix(value):
+        if isinstance(value, types.MethodType):
+            name = describe(None, value.__self__, verbose=True) + '.'
+        else:
+            module = inspect.getmodule(value)
+            if module is not None and module.__name__ != "builtins":
+                name = module.__name__ + '.'
+            else:
+                name = ""
+        return name
+
 
 class TypeFromClasses(ClassBasedTraitType):
     """A trait whose value must be a subclass of a class in a specified list of classes."""
@@ -287,7 +298,7 @@ class or its subclasses.  Our implementation is quite different
             self.klasses = klasses
         else:
             raise TraitError('The klasses attribute must be a list of class names or classes'
-                                ' not: %r' % klass)
+                                ' not: %r' % klasses)
 
         if (kw is not None) and not isinstance(kw, dict):
             raise TraitError("The 'kw' argument must be a dict or None.")
@@ -350,4 +361,4 @@ def default_value_repr(self):
         return repr(self.make_dynamic_default())
 
     def from_string(self, s):
-        return _safe_literal_eval(s)
+        return literal_eval(s)
diff --git a/jupyter_server/utils.py b/jupyter_server/utils.py
index 7af3c3a524..9a062dfc03 100644
--- a/jupyter_server/utils.py
+++ b/jupyter_server/utils.py
@@ -14,13 +14,12 @@
 from distutils.version import LooseVersion
 from contextlib import contextmanager
 
-from urllib.parse import (quote, unquote, urlparse, urljoin,
+from urllib.parse import (quote, unquote, urlparse,
     urlsplit, urlunsplit, SplitResult)
-from urllib.request import pathname2url
-
+from urllib.parse import urljoin  # pylint: disable=unused-import
+from urllib.request import pathname2url  # pylint: disable=unused-import
 from tornado.httpclient import AsyncHTTPClient, HTTPClient, HTTPRequest
 from tornado.netutil import Resolver
-from tornado.ioloop import IOLoop
 
 
 def url_path_join(*pieces):
diff --git a/setup.cfg b/setup.cfg
index 07572b147a..1b27f53ff6 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -63,3 +63,12 @@ console_scripts =
 
 [options.packages.find]
 exclude = ['docs*', 'examples*']
+
+[flake8]
+ignore = E, C, W, F401, F403, F811, F841, E402, I100, I101, D400
+builtins = c, get_config
+exclude =
+    .cache,
+    .github,
+    docs,
+    setup.py