diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 3a850f71..bf7a5c81 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -19,10 +19,10 @@ jobs:
         id: tag
         run: echo ::set-output name=tag::${GITHUB_REF#refs/tags/}
 
-      - name: Set up Python 3.9
+      - name: Set up Python 3.11
         uses: actions/setup-python@v4
         with:
-          python-version: "3.9"
+          python-version: "3.11"
 
       - name: Install and set up Poetry
         run: |
@@ -44,8 +44,9 @@ jobs:
         uses: ncipollo/release-action@v1
         with:
           artifacts: "dist/*"
-          token: ${{ secrets.GITHUB_TOKEN }}
           draft: false
+          allowUpdates: true
+          generateReleaseNotes: true
           prerelease: steps.check-version.outputs.prerelease == 'true'
 
       - name: Publish to PyPI
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 781e0ff6..d7a65549 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,18 @@
 # Change Log
 
+## [0.12.0] - 2023-07-27
+
+### Added
+
+- Allow users to specify encoders for custom types. ([#296](https://github.com/sdispater/tomlkit/issues/296))
+
+### Fixed
+
+- Fix the incorrect sort when building a table with dotted keys.
+- Complete the methods required for integer and float items. ([#307](https://github.com/sdispater/tomlkit/issues/307))
+- Replace the deprecated usage of `datetime.utcnow()`. ([#308](https://github.com/sdispater/tomlkit/issues/308))
+- Minor performance improvements when iterating over the escape sequences. ([#304](https://github.com/sdispater/tomlkit/issues/304))
+
 ## [0.11.8] - 2023-04-27
 
 ### Fixed
@@ -346,7 +359,8 @@
 - Fixed handling of super tables with different sections.
 - Fixed raw strings escaping.
 
-[unreleased]: https://github.com/sdispater/tomlkit/compare/0.11.8...master
+[unreleased]: https://github.com/sdispater/tomlkit/compare/0.12.0...master
+[0.12.0]: https://github.com/sdispater/tomlkit/releases/tag/0.12.0
 [0.11.8]: https://github.com/sdispater/tomlkit/releases/tag/0.11.8
 [0.11.7]: https://github.com/sdispater/tomlkit/releases/tag/0.11.7
 [0.11.6]: https://github.com/sdispater/tomlkit/releases/tag/0.11.6
diff --git a/README.md b/README.md
index 641e7cbc..0d4701d6 100644
--- a/README.md
+++ b/README.md
@@ -24,7 +24,7 @@ Part of the implementation has been adapted, improved and fixed from [Molten](ht
 
 ## Usage
 
-See the [documentation](https://github.com/sdispater/tomlkit/blob/master/docs/quickstart.rst) for more information.
+See the [documentation](https://tomlkit.readthedocs.io/) for more information.
 
 ## Installation
 
diff --git a/poetry.lock b/poetry.lock
index ef441b90..21711ca4 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1,10 +1,9 @@
-# This file is automatically @generated by Poetry and should not be changed by hand.
+# This file is automatically @generated by Poetry 1.5.1 and should not be changed by hand.
 
 [[package]]
 name = "alabaster"
 version = "0.7.13"
 description = "A configurable sidebar-enabled Sphinx theme"
-category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -16,7 +15,6 @@ files = [
 name = "attrs"
 version = "22.2.0"
 description = "Classes Without Boilerplate"
-category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -35,7 +33,6 @@ tests-no-zope = ["cloudpickle", "cloudpickle", "hypothesis", "hypothesis", "mypy
 name = "babel"
 version = "2.11.0"
 description = "Internationalization utilities"
-category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -50,7 +47,6 @@ pytz = ">=2015.7"
 name = "beautifulsoup4"
 version = "4.11.1"
 description = "Screen-scraping library"
-category = "dev"
 optional = false
 python-versions = ">=3.6.0"
 files = [
@@ -67,21 +63,19 @@ lxml = ["lxml"]
 
 [[package]]
 name = "certifi"
-version = "2022.12.7"
+version = "2023.7.22"
 description = "Python package for providing Mozilla's CA Bundle."
-category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
-    {file = "certifi-2022.12.7-py3-none-any.whl", hash = "sha256:4ad3232f5e926d6718ec31cfc1fcadfde020920e278684144551c91769c7bc18"},
-    {file = "certifi-2022.12.7.tar.gz", hash = "sha256:35824b4c3a97115964b408844d64aa14db1cc518f6562e8d7261699d1350a9e3"},
+    {file = "certifi-2023.7.22-py3-none-any.whl", hash = "sha256:92d6037539857d8206b8f6ae472e8b77db8058fec5937a1ef3f54304089edbb9"},
+    {file = "certifi-2023.7.22.tar.gz", hash = "sha256:539cc1d13202e33ca466e88b2807e29f4c13049d6d87031a3c110744495cb082"},
 ]
 
 [[package]]
 name = "cfgv"
 version = "3.3.1"
 description = "Validate configuration and produce human readable error messages."
-category = "dev"
 optional = false
 python-versions = ">=3.6.1"
 files = [
@@ -93,7 +87,6 @@ files = [
 name = "charset-normalizer"
 version = "2.0.12"
 description = "The Real First Universal Charset Detector. Open, modern and actively maintained alternative to Chardet."
-category = "dev"
 optional = false
 python-versions = ">=3.5.0"
 files = [
@@ -108,7 +101,6 @@ unicode-backport = ["unicodedata2"]
 name = "colorama"
 version = "0.4.6"
 description = "Cross-platform colored terminal text."
-category = "dev"
 optional = false
 python-versions = "!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*,!=3.5.*,!=3.6.*,>=2.7"
 files = [
@@ -120,7 +112,6 @@ files = [
 name = "coverage"
 version = "7.1.0"
 description = "Code coverage measurement for Python"
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -187,7 +178,6 @@ toml = ["tomli"]
 name = "distlib"
 version = "0.3.6"
 description = "Distribution utilities"
-category = "dev"
 optional = false
 python-versions = "*"
 files = [
@@ -199,7 +189,6 @@ files = [
 name = "docutils"
 version = "0.17.1"
 description = "Docutils -- Python Documentation Utilities"
-category = "dev"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
 files = [
@@ -211,7 +200,6 @@ files = [
 name = "exceptiongroup"
 version = "1.1.0"
 description = "Backport of PEP 654 (exception groups)"
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -226,7 +214,6 @@ test = ["pytest (>=6)"]
 name = "filelock"
 version = "3.9.0"
 description = "A platform independent file lock."
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -242,7 +229,6 @@ testing = ["covdefaults (>=2.2.2)", "coverage (>=7.0.1)", "pytest (>=7.2)", "pyt
 name = "furo"
 version = "2022.9.29"
 description = "A clean customisable Sphinx documentation theme."
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -260,7 +246,6 @@ sphinx-basic-ng = "*"
 name = "identify"
 version = "2.5.16"
 description = "File identification library for Python"
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -275,7 +260,6 @@ license = ["ukkonen"]
 name = "idna"
 version = "3.4"
 description = "Internationalized Domain Names in Applications (IDNA)"
-category = "dev"
 optional = false
 python-versions = ">=3.5"
 files = [
@@ -287,7 +271,6 @@ files = [
 name = "imagesize"
 version = "1.4.1"
 description = "Getting image size from png/jpeg/jpeg2000/gif file"
-category = "dev"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
 files = [
@@ -299,7 +282,6 @@ files = [
 name = "importlib-metadata"
 version = "6.0.0"
 description = "Read metadata from Python packages"
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -320,7 +302,6 @@ testing = ["flake8 (<5)", "flufl.flake8", "importlib-resources (>=1.3)", "packag
 name = "iniconfig"
 version = "2.0.0"
 description = "brain-dead simple config-ini parsing"
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -332,7 +313,6 @@ files = [
 name = "jinja2"
 version = "3.1.2"
 description = "A very fast and expressive template engine."
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -350,7 +330,6 @@ i18n = ["Babel (>=2.7)"]
 name = "markupsafe"
 version = "2.1.2"
 description = "Safely add untrusted strings to HTML/XML markup."
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -410,7 +389,6 @@ files = [
 name = "mypy"
 version = "0.990"
 description = "Optional static typing for Python"
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -462,7 +440,6 @@ reports = ["lxml"]
 name = "mypy-extensions"
 version = "0.4.3"
 description = "Experimental type system extensions for programs checked with the mypy typechecker."
-category = "dev"
 optional = false
 python-versions = "*"
 files = [
@@ -474,7 +451,6 @@ files = [
 name = "nodeenv"
 version = "1.7.0"
 description = "Node.js virtual environment builder"
-category = "dev"
 optional = false
 python-versions = ">=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*,!=3.5.*,!=3.6.*"
 files = [
@@ -489,7 +465,6 @@ setuptools = "*"
 name = "packaging"
 version = "23.0"
 description = "Core utilities for Python packages"
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -501,7 +476,6 @@ files = [
 name = "platformdirs"
 version = "2.6.2"
 description = "A small Python package for determining appropriate platform-specific dirs, e.g. a \"user data dir\"."
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -520,7 +494,6 @@ test = ["appdirs (==1.4.4)", "covdefaults (>=2.2.2)", "pytest (>=7.2)", "pytest-
 name = "pluggy"
 version = "1.0.0"
 description = "plugin and hook calling mechanisms for python"
-category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -539,7 +512,6 @@ testing = ["pytest", "pytest-benchmark"]
 name = "pre-commit"
 version = "2.21.0"
 description = "A framework for managing and maintaining multi-language pre-commit hooks."
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -557,14 +529,13 @@ virtualenv = ">=20.10.0"
 
 [[package]]
 name = "pygments"
-version = "2.14.0"
+version = "2.15.0"
 description = "Pygments is a syntax highlighting package written in Python."
-category = "dev"
 optional = false
-python-versions = ">=3.6"
+python-versions = ">=3.7"
 files = [
-    {file = "Pygments-2.14.0-py3-none-any.whl", hash = "sha256:fa7bd7bd2771287c0de303af8bfdfc731f51bd2c6a47ab69d117138893b82717"},
-    {file = "Pygments-2.14.0.tar.gz", hash = "sha256:b3ed06a9e8ac9a9aae5a6f5dbe78a8a58655d17b43b93c078f094ddc476ae297"},
+    {file = "Pygments-2.15.0-py3-none-any.whl", hash = "sha256:77a3299119af881904cd5ecd1ac6a66214b6e9bed1f2db16993b54adede64094"},
+    {file = "Pygments-2.15.0.tar.gz", hash = "sha256:f7e36cffc4c517fbc252861b9a6e4644ca0e5abadf9a113c72d1358ad09b9500"},
 ]
 
 [package.extras]
@@ -574,7 +545,6 @@ plugins = ["importlib-metadata"]
 name = "pytest"
 version = "7.2.1"
 description = "pytest: simple powerful testing with Python"
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -599,7 +569,6 @@ testing = ["argcomplete", "hypothesis (>=3.56)", "mock", "nose", "pygments (>=2.
 name = "pytest-cov"
 version = "4.0.0"
 description = "Pytest plugin for measuring coverage."
-category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -618,7 +587,6 @@ testing = ["fields", "hunter", "process-tests", "pytest-xdist", "six", "virtuale
 name = "pytz"
 version = "2022.7.1"
 description = "World timezone definitions, modern and historical"
-category = "dev"
 optional = false
 python-versions = "*"
 files = [
@@ -630,7 +598,6 @@ files = [
 name = "pyyaml"
 version = "6.0"
 description = "YAML parser and emitter for Python"
-category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -678,31 +645,29 @@ files = [
 
 [[package]]
 name = "requests"
-version = "2.27.1"
+version = "2.31.0"
 description = "Python HTTP for Humans."
-category = "dev"
 optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*, !=3.5.*"
+python-versions = ">=3.7"
 files = [
-    {file = "requests-2.27.1-py2.py3-none-any.whl", hash = "sha256:f22fa1e554c9ddfd16e6e41ac79759e17be9e492b3587efa038054674760e72d"},
-    {file = "requests-2.27.1.tar.gz", hash = "sha256:68d7c56fd5a8999887728ef304a6d12edc7be74f1cfa47714fc8b414525c9a61"},
+    {file = "requests-2.31.0-py3-none-any.whl", hash = "sha256:58cd2187c01e70e6e26505bca751777aa9f2ee0b7f4300988b709f44e013003f"},
+    {file = "requests-2.31.0.tar.gz", hash = "sha256:942c5a758f98d790eaed1a29cb6eefc7ffb0d1cf7af05c3d2791656dbd6ad1e1"},
 ]
 
 [package.dependencies]
 certifi = ">=2017.4.17"
-charset-normalizer = {version = ">=2.0.0,<2.1.0", markers = "python_version >= \"3\""}
-idna = {version = ">=2.5,<4", markers = "python_version >= \"3\""}
-urllib3 = ">=1.21.1,<1.27"
+charset-normalizer = ">=2,<4"
+idna = ">=2.5,<4"
+urllib3 = ">=1.21.1,<3"
 
 [package.extras]
-socks = ["PySocks (>=1.5.6,!=1.5.7)", "win-inet-pton"]
-use-chardet-on-py3 = ["chardet (>=3.0.2,<5)"]
+socks = ["PySocks (>=1.5.6,!=1.5.7)"]
+use-chardet-on-py3 = ["chardet (>=3.0.2,<6)"]
 
 [[package]]
 name = "setuptools"
 version = "67.0.0"
 description = "Easily download, build, install, upgrade, and uninstall Python packages"
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -719,7 +684,6 @@ testing-integration = ["build[virtualenv]", "filelock (>=3.4.0)", "jaraco.envs (
 name = "snowballstemmer"
 version = "2.2.0"
 description = "This package provides 29 stemmers for 28 languages generated from Snowball algorithms."
-category = "dev"
 optional = false
 python-versions = "*"
 files = [
@@ -731,7 +695,6 @@ files = [
 name = "soupsieve"
 version = "2.3.2.post1"
 description = "A modern CSS selector implementation for Beautiful Soup."
-category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -743,7 +706,6 @@ files = [
 name = "sphinx"
 version = "4.5.0"
 description = "Python documentation generator"
-category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -779,7 +741,6 @@ test = ["cython", "html5lib", "pytest", "pytest-cov", "typed-ast"]
 name = "sphinx-basic-ng"
 version = "1.0.0b1"
 description = "A modern skeleton for Sphinx themes."
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -797,7 +758,6 @@ docs = ["furo", "ipython", "myst-parser", "sphinx-copybutton", "sphinx-inline-ta
 name = "sphinxcontrib-applehelp"
 version = "1.0.2"
 description = "sphinxcontrib-applehelp is a sphinx extension which outputs Apple help books"
-category = "dev"
 optional = false
 python-versions = ">=3.5"
 files = [
@@ -813,7 +773,6 @@ test = ["pytest"]
 name = "sphinxcontrib-devhelp"
 version = "1.0.2"
 description = "sphinxcontrib-devhelp is a sphinx extension which outputs Devhelp document."
-category = "dev"
 optional = false
 python-versions = ">=3.5"
 files = [
@@ -829,7 +788,6 @@ test = ["pytest"]
 name = "sphinxcontrib-htmlhelp"
 version = "2.0.0"
 description = "sphinxcontrib-htmlhelp is a sphinx extension which renders HTML help files"
-category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -845,7 +803,6 @@ test = ["html5lib", "pytest"]
 name = "sphinxcontrib-jsmath"
 version = "1.0.1"
 description = "A sphinx extension which renders display math in HTML via JavaScript"
-category = "dev"
 optional = false
 python-versions = ">=3.5"
 files = [
@@ -860,7 +817,6 @@ test = ["flake8", "mypy", "pytest"]
 name = "sphinxcontrib-qthelp"
 version = "1.0.3"
 description = "sphinxcontrib-qthelp is a sphinx extension which outputs QtHelp document."
-category = "dev"
 optional = false
 python-versions = ">=3.5"
 files = [
@@ -876,7 +832,6 @@ test = ["pytest"]
 name = "sphinxcontrib-serializinghtml"
 version = "1.1.5"
 description = "sphinxcontrib-serializinghtml is a sphinx extension which outputs \"serialized\" HTML files (json and pickle)."
-category = "dev"
 optional = false
 python-versions = ">=3.5"
 files = [
@@ -892,7 +847,6 @@ test = ["pytest"]
 name = "tomli"
 version = "2.0.1"
 description = "A lil' TOML parser"
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -904,7 +858,6 @@ files = [
 name = "typed-ast"
 version = "1.5.4"
 description = "a fork of Python 2 and 3 ast modules with type comment support"
-category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -938,7 +891,6 @@ files = [
 name = "typing-extensions"
 version = "4.4.0"
 description = "Backported and Experimental Type Hints for Python 3.7+"
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
@@ -950,7 +902,6 @@ files = [
 name = "urllib3"
 version = "1.26.14"
 description = "HTTP library with thread-safe connection pooling, file post, and more."
-category = "dev"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*, !=3.5.*"
 files = [
@@ -967,7 +918,6 @@ socks = ["PySocks (>=1.5.6,!=1.5.7,<2.0)"]
 name = "virtualenv"
 version = "20.17.1"
 description = "Virtual Python Environment builder"
-category = "dev"
 optional = false
 python-versions = ">=3.6"
 files = [
@@ -989,7 +939,6 @@ testing = ["coverage (>=6.2)", "coverage-enable-subprocess (>=1)", "flaky (>=3.7
 name = "zipp"
 version = "3.12.0"
 description = "Backport of pathlib-compatible object wrapper for zip files"
-category = "dev"
 optional = false
 python-versions = ">=3.7"
 files = [
diff --git a/pyproject.toml b/pyproject.toml
index 2ce869b4..ac0807a8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "tomlkit"
-version = "0.11.8"
+version = "0.12.0"
 description = "Style preserving TOML library"
 authors = [
     "Sébastien Eustace <sebastien@eustace.io>",
diff --git a/tests/test_items.py b/tests/test_items.py
index 45aea258..783cab37 100644
--- a/tests/test_items.py
+++ b/tests/test_items.py
@@ -6,6 +6,7 @@
 from datetime import datetime
 from datetime import time
 from datetime import timedelta
+from datetime import timezone
 
 import pytest
 
@@ -103,7 +104,7 @@ def test_true_unwrap():
 
 
 def test_datetime_unwrap():
-    dt = datetime.utcnow()
+    dt = datetime.now(tz=timezone.utc)
     elementary_test(item(dt), datetime)
 
 
@@ -946,3 +947,21 @@ def test_copy_copy():
 )
 def test_escape_key(key_str, escaped):
     assert api.key(key_str).as_string() == escaped
+
+
+def test_custom_encoders():
+    import decimal
+
+    @api.register_encoder
+    def encode_decimal(obj):
+        if isinstance(obj, decimal.Decimal):
+            return api.float_(str(obj))
+        raise TypeError
+
+    assert api.item(decimal.Decimal("1.23")).as_string() == "1.23"
+
+    with pytest.raises(TypeError):
+        api.item(object())
+
+    assert api.dumps({"foo": decimal.Decimal("1.23")}) == "foo = 1.23\n"
+    api.unregister_encoder(encode_decimal)
diff --git a/tests/test_toml_document.py b/tests/test_toml_document.py
index faadae41..eb4b3743 100644
--- a/tests/test_toml_document.py
+++ b/tests/test_toml_document.py
@@ -1072,3 +1072,15 @@ def test_parse_subtables_no_extra_indent():
 """
     doc = parse(expected)
     assert doc.as_string() == expected
+
+
+def test_item_preserves_the_order():
+    t = tomlkit.inline_table()
+    t.update({"a": 1, "b": 2})
+    doc = {"name": "foo", "table": t, "age": 42}
+    expected = """\
+name = "foo"
+table = {a = 1, b = 2}
+age = 42
+"""
+    assert tomlkit.dumps(doc) == expected
diff --git a/tomlkit/__init__.py b/tomlkit/__init__.py
index acc7046c..1236d017 100644
--- a/tomlkit/__init__.py
+++ b/tomlkit/__init__.py
@@ -18,14 +18,16 @@
 from tomlkit.api import loads
 from tomlkit.api import nl
 from tomlkit.api import parse
+from tomlkit.api import register_encoder
 from tomlkit.api import string
 from tomlkit.api import table
 from tomlkit.api import time
+from tomlkit.api import unregister_encoder
 from tomlkit.api import value
 from tomlkit.api import ws
 
 
-__version__ = "0.11.8"
+__version__ = "0.12.0"
 __all__ = [
     "aot",
     "array",
@@ -52,4 +54,6 @@
     "TOMLDocument",
     "value",
     "ws",
+    "register_encoder",
+    "unregister_encoder",
 ]
diff --git a/tomlkit/_types.py b/tomlkit/_types.py
new file mode 100644
index 00000000..cc1847b5
--- /dev/null
+++ b/tomlkit/_types.py
@@ -0,0 +1,65 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+from typing import Any
+from typing import TypeVar
+
+
+WT = TypeVar("WT", bound="WrapperType")
+
+if TYPE_CHECKING:  # pragma: no cover
+    # Define _CustomList and _CustomDict as a workaround for:
+    # https://github.com/python/mypy/issues/11427
+    #
+    # According to this issue, the typeshed contains a "lie"
+    # (it adds MutableSequence to the ancestry of list and MutableMapping to
+    # the ancestry of dict) which completely messes with the type inference for
+    # Table, InlineTable, Array and Container.
+    #
+    # Importing from builtins is preferred over simple assignment, see issues:
+    # https://github.com/python/mypy/issues/8715
+    # https://github.com/python/mypy/issues/10068
+    from builtins import dict as _CustomDict  # noqa: N812
+    from builtins import float as _CustomFloat  # noqa: N812
+    from builtins import int as _CustomInt  # noqa: N812
+    from builtins import list as _CustomList  # noqa: N812
+    from typing import Callable
+    from typing import Concatenate
+    from typing import ParamSpec
+    from typing import Protocol
+
+    P = ParamSpec("P")
+
+    class WrapperType(Protocol):
+        def _new(self: WT, value: Any) -> WT:
+            ...
+
+else:
+    from collections.abc import MutableMapping
+    from collections.abc import MutableSequence
+    from numbers import Integral
+    from numbers import Real
+
+    class _CustomList(MutableSequence, list):
+        """Adds MutableSequence mixin while pretending to be a builtin list"""
+
+    class _CustomDict(MutableMapping, dict):
+        """Adds MutableMapping mixin while pretending to be a builtin dict"""
+
+    class _CustomInt(Integral, int):
+        """Adds Integral mixin while pretending to be a builtin int"""
+
+    class _CustomFloat(Real, float):
+        """Adds Real mixin while pretending to be a builtin float"""
+
+
+def wrap_method(
+    original_method: Callable[Concatenate[WT, P], Any]
+) -> Callable[Concatenate[WT, P], Any]:
+    def wrapper(self: WT, *args: P.args, **kwargs: P.kwargs) -> Any:
+        result = original_method(self, *args, **kwargs)
+        if result is NotImplemented:
+            return result
+        return self._new(result)
+
+    return wrapper
diff --git a/tomlkit/_utils.py b/tomlkit/_utils.py
index a6ed9c64..f87fd7b5 100644
--- a/tomlkit/_utils.py
+++ b/tomlkit/_utils.py
@@ -133,9 +133,11 @@ def flush(inc=1):
 
         return i + inc
 
+    found_sequences = {seq for seq in escape_sequences if seq in s}
+
     i = 0
     while i < len(s):
-        for seq in escape_sequences:
+        for seq in found_sequences:
             seq_len = len(seq)
             if s[i:].startswith(seq):
                 start = flush(seq_len)
diff --git a/tomlkit/api.py b/tomlkit/api.py
index 8ec5653c..686fd1c0 100644
--- a/tomlkit/api.py
+++ b/tomlkit/api.py
@@ -1,14 +1,17 @@
 from __future__ import annotations
 
+import contextlib
 import datetime as _datetime
 
 from collections.abc import Mapping
 from typing import IO
 from typing import Iterable
+from typing import TypeVar
 
 from tomlkit._utils import parse_rfc3339
 from tomlkit.container import Container
 from tomlkit.exceptions import UnexpectedCharError
+from tomlkit.items import CUSTOM_ENCODERS
 from tomlkit.items import AoT
 from tomlkit.items import Array
 from tomlkit.items import Bool
@@ -16,6 +19,7 @@
 from tomlkit.items import Date
 from tomlkit.items import DateTime
 from tomlkit.items import DottedKey
+from tomlkit.items import Encoder
 from tomlkit.items import Float
 from tomlkit.items import InlineTable
 from tomlkit.items import Integer
@@ -284,3 +288,21 @@ def nl() -> Whitespace:
 def comment(string: str) -> Comment:
     """Create a comment item."""
     return Comment(Trivia(comment_ws="  ", comment="# " + string))
+
+
+E = TypeVar("E", bound=Encoder)
+
+
+def register_encoder(encoder: E) -> E:
+    """Add a custom encoder, which should be a function that will be called
+    if the value can't otherwise be converted. It should takes a single value
+    and return a TOMLKit item or raise a ``TypeError``.
+    """
+    CUSTOM_ENCODERS.append(encoder)
+    return encoder
+
+
+def unregister_encoder(encoder: Encoder) -> None:
+    """Unregister a custom encoder."""
+    with contextlib.suppress(ValueError):
+        CUSTOM_ENCODERS.remove(encoder)
diff --git a/tomlkit/container.py b/tomlkit/container.py
index 66448754..27d69170 100644
--- a/tomlkit/container.py
+++ b/tomlkit/container.py
@@ -6,6 +6,7 @@
 from typing import Iterator
 
 from tomlkit._compat import decode
+from tomlkit._types import _CustomDict
 from tomlkit._utils import merge_dicts
 from tomlkit.exceptions import KeyAlreadyPresent
 from tomlkit.exceptions import NonExistentKey
@@ -19,7 +20,6 @@
 from tomlkit.items import Table
 from tomlkit.items import Trivia
 from tomlkit.items import Whitespace
-from tomlkit.items import _CustomDict
 from tomlkit.items import item as _item
 
 
diff --git a/tomlkit/items.py b/tomlkit/items.py
index 74c3e785..853754a7 100644
--- a/tomlkit/items.py
+++ b/tomlkit/items.py
@@ -3,8 +3,10 @@
 import abc
 import copy
 import dataclasses
+import math
 import re
 import string
+import sys
 
 from datetime import date
 from datetime import datetime
@@ -13,6 +15,7 @@
 from enum import Enum
 from typing import TYPE_CHECKING
 from typing import Any
+from typing import Callable
 from typing import Collection
 from typing import Iterable
 from typing import Iterator
@@ -23,40 +26,31 @@
 
 from tomlkit._compat import PY38
 from tomlkit._compat import decode
+from tomlkit._types import _CustomDict
+from tomlkit._types import _CustomFloat
+from tomlkit._types import _CustomInt
+from tomlkit._types import _CustomList
+from tomlkit._types import wrap_method
 from tomlkit._utils import CONTROL_CHARS
 from tomlkit._utils import escape_string
 from tomlkit.exceptions import InvalidStringError
 
 
-if TYPE_CHECKING:  # pragma: no cover
-    # Define _CustomList and _CustomDict as a workaround for:
-    # https://github.com/python/mypy/issues/11427
-    #
-    # According to this issue, the typeshed contains a "lie"
-    # (it adds MutableSequence to the ancestry of list and MutableMapping to
-    # the ancestry of dict) which completely messes with the type inference for
-    # Table, InlineTable, Array and Container.
-    #
-    # Importing from builtins is preferred over simple assignment, see issues:
-    # https://github.com/python/mypy/issues/8715
-    # https://github.com/python/mypy/issues/10068
-    from builtins import dict as _CustomDict  # noqa: N812, TC004
-    from builtins import list as _CustomList  # noqa: N812, TC004
-
-    # Allow type annotations but break circular imports
+if TYPE_CHECKING:
     from tomlkit import container
-else:
-    from collections.abc import MutableMapping
-    from collections.abc import MutableSequence
 
-    class _CustomList(MutableSequence, list):
-        """Adds MutableSequence mixin while pretending to be a builtin list"""
 
-    class _CustomDict(MutableMapping, dict):
-        """Adds MutableMapping mixin while pretending to be a builtin dict"""
+ItemT = TypeVar("ItemT", bound="Item")
+Encoder = Callable[[Any], "Item"]
+CUSTOM_ENCODERS: list[Encoder] = []
+AT = TypeVar("AT", bound="AbstractTable")
 
 
-ItemT = TypeVar("ItemT", bound="Item")
+class _ConvertError(TypeError, ValueError):
+    """An internal error raised when item() fails to convert a value.
+    It should be a TypeError, but due to historical reasons
+    it needs to subclass ValueError as well.
+    """
 
 
 @overload
@@ -155,7 +149,7 @@ def item(value: Any, _parent: Item | None = None, _sort_keys: bool = False) -> I
         val = table_constructor(Container(), Trivia(), False)
         for k, v in sorted(
             value.items(),
-            key=lambda i: (isinstance(i[1], dict), i[0] if _sort_keys else 1),
+            key=lambda i: (isinstance(i[1], dict), i[0]) if _sort_keys else 1,
         ):
             val[k] = item(v, _parent=val, _sort_keys=_sort_keys)
 
@@ -218,8 +212,20 @@ def item(value: Any, _parent: Item | None = None, _sort_keys: bool = False) -> I
             Trivia(),
             value.isoformat(),
         )
+    else:
+        for encoder in CUSTOM_ENCODERS:
+            try:
+                rv = encoder(value)
+            except TypeError:
+                pass
+            else:
+                if not isinstance(rv, Item):
+                    raise _ConvertError(
+                        f"Custom encoder returned {type(rv)}, not a subclass of Item"
+                    )
+                return rv
 
-    raise ValueError(f"Invalid type {type(value)}")
+    raise _ConvertError(f"Invalid type {type(value)}")
 
 
 class StringType(Enum):
@@ -434,7 +440,7 @@ def __eq__(self, other: Any) -> bool:
 class DottedKey(Key):
     def __init__(
         self,
-        keys: Iterable[Key],
+        keys: Iterable[SingleKey],
         sep: str | None = None,
         original: str | None = None,
     ) -> None:
@@ -584,17 +590,17 @@ def __str__(self) -> str:
         return f"{self._trivia.indent}{decode(self._trivia.comment)}"
 
 
-class Integer(int, Item):
+class Integer(Item, _CustomInt):
     """
     An integer literal.
     """
 
     def __new__(cls, value: int, trivia: Trivia, raw: str) -> Integer:
-        return super().__new__(cls, value)
+        return int.__new__(cls, value)
 
-    def __init__(self, _: int, trivia: Trivia, raw: str) -> None:
+    def __init__(self, value: int, trivia: Trivia, raw: str) -> None:
         super().__init__(trivia)
-
+        self._original = value
         self._raw = raw
         self._sign = False
 
@@ -602,7 +608,9 @@ def __init__(self, _: int, trivia: Trivia, raw: str) -> None:
             self._sign = True
 
     def unwrap(self) -> int:
-        return int(self)
+        return self._original
+
+    __int__ = unwrap
 
     @property
     def discriminant(self) -> int:
@@ -616,30 +624,6 @@ def value(self) -> int:
     def as_string(self) -> str:
         return self._raw
 
-    def __add__(self, other):
-        result = super().__add__(other)
-        if result is NotImplemented:
-            return result
-        return self._new(result)
-
-    def __radd__(self, other):
-        result = super().__radd__(other)
-        if result is NotImplemented:
-            return result
-        return self._new(result)
-
-    def __sub__(self, other):
-        result = super().__sub__(other)
-        if result is NotImplemented:
-            return result
-        return self._new(result)
-
-    def __rsub__(self, other):
-        result = super().__rsub__(other)
-        if result is NotImplemented:
-            return result
-        return self._new(result)
-
     def _new(self, result):
         raw = str(result)
         if self._sign:
@@ -651,18 +635,53 @@ def _new(self, result):
     def _getstate(self, protocol=3):
         return int(self), self._trivia, self._raw
 
-
-class Float(float, Item):
+    # int methods
+    __abs__ = wrap_method(int.__abs__)
+    __add__ = wrap_method(int.__add__)
+    __and__ = wrap_method(int.__and__)
+    __ceil__ = wrap_method(int.__ceil__)
+    __eq__ = int.__eq__
+    __floor__ = wrap_method(int.__floor__)
+    __floordiv__ = wrap_method(int.__floordiv__)
+    __invert__ = wrap_method(int.__invert__)
+    __le__ = int.__le__
+    __lshift__ = wrap_method(int.__lshift__)
+    __lt__ = int.__lt__
+    __mod__ = wrap_method(int.__mod__)
+    __mul__ = wrap_method(int.__mul__)
+    __neg__ = wrap_method(int.__neg__)
+    __or__ = wrap_method(int.__or__)
+    __pos__ = wrap_method(int.__pos__)
+    __pow__ = wrap_method(int.__pow__)
+    __radd__ = wrap_method(int.__radd__)
+    __rand__ = wrap_method(int.__rand__)
+    __rfloordiv__ = wrap_method(int.__rfloordiv__)
+    __rlshift__ = wrap_method(int.__rlshift__)
+    __rmod__ = wrap_method(int.__rmod__)
+    __rmul__ = wrap_method(int.__rmul__)
+    __ror__ = wrap_method(int.__ror__)
+    __round__ = wrap_method(int.__round__)
+    __rpow__ = wrap_method(int.__rpow__)
+    __rrshift__ = wrap_method(int.__rrshift__)
+    __rshift__ = wrap_method(int.__rshift__)
+    __rtruediv__ = wrap_method(int.__rtruediv__)
+    __rxor__ = wrap_method(int.__rxor__)
+    __truediv__ = wrap_method(int.__truediv__)
+    __trunc__ = wrap_method(int.__trunc__)
+    __xor__ = wrap_method(int.__xor__)
+
+
+class Float(Item, _CustomFloat):
     """
     A float literal.
     """
 
-    def __new__(cls, value: float, trivia: Trivia, raw: str) -> Integer:
-        return super().__new__(cls, value)
+    def __new__(cls, value: float, trivia: Trivia, raw: str) -> Float:
+        return float.__new__(cls, value)
 
-    def __init__(self, _: float, trivia: Trivia, raw: str) -> None:
+    def __init__(self, value: float, trivia: Trivia, raw: str) -> None:
         super().__init__(trivia)
-
+        self._original = value
         self._raw = raw
         self._sign = False
 
@@ -670,7 +689,9 @@ def __init__(self, _: float, trivia: Trivia, raw: str) -> None:
             self._sign = True
 
     def unwrap(self) -> float:
-        return float(self)
+        return self._original
+
+    __float__ = unwrap
 
     @property
     def discriminant(self) -> int:
@@ -684,32 +705,6 @@ def value(self) -> float:
     def as_string(self) -> str:
         return self._raw
 
-    def __add__(self, other):
-        result = super().__add__(other)
-
-        return self._new(result)
-
-    def __radd__(self, other):
-        result = super().__radd__(other)
-
-        if isinstance(other, Float):
-            return self._new(result)
-
-        return result
-
-    def __sub__(self, other):
-        result = super().__sub__(other)
-
-        return self._new(result)
-
-    def __rsub__(self, other):
-        result = super().__rsub__(other)
-
-        if isinstance(other, Float):
-            return self._new(result)
-
-        return result
-
     def _new(self, result):
         raw = str(result)
 
@@ -722,6 +717,35 @@ def _new(self, result):
     def _getstate(self, protocol=3):
         return float(self), self._trivia, self._raw
 
+    # float methods
+    __abs__ = wrap_method(float.__abs__)
+    __add__ = wrap_method(float.__add__)
+    __eq__ = float.__eq__
+    __floordiv__ = wrap_method(float.__floordiv__)
+    __le__ = float.__le__
+    __lt__ = float.__lt__
+    __mod__ = wrap_method(float.__mod__)
+    __mul__ = wrap_method(float.__mul__)
+    __neg__ = wrap_method(float.__neg__)
+    __pos__ = wrap_method(float.__pos__)
+    __pow__ = wrap_method(float.__pow__)
+    __radd__ = wrap_method(float.__radd__)
+    __rfloordiv__ = wrap_method(float.__rfloordiv__)
+    __rmod__ = wrap_method(float.__rmod__)
+    __rmul__ = wrap_method(float.__rmul__)
+    __round__ = wrap_method(float.__round__)
+    __rpow__ = wrap_method(float.__rpow__)
+    __rtruediv__ = wrap_method(float.__rtruediv__)
+    __truediv__ = wrap_method(float.__truediv__)
+    __trunc__ = float.__trunc__
+
+    if sys.version_info >= (3, 9):
+        __ceil__ = float.__ceil__
+        __floor__ = float.__floor__
+    else:
+        __ceil__ = math.ceil
+        __floor__ = math.floor
+
 
 class Bool(Item):
     """
@@ -1388,9 +1412,6 @@ def _getstate(self, protocol=3):
         return list(self._iter_items()), self._trivia, self._multiline
 
 
-AT = TypeVar("AT", bound="AbstractTable")
-
-
 class AbstractTable(Item, _CustomDict):
     """Common behaviour of both :class:`Table` and :class:`InlineTable`"""
 
@@ -1430,11 +1451,11 @@ def append(self, key, value):
         raise NotImplementedError
 
     @overload
-    def add(self: AT, value: Comment | Whitespace) -> AT:
+    def add(self: AT, key: Comment | Whitespace) -> AT:
         ...
 
     @overload
-    def add(self: AT, key: Key | str, value: Any) -> AT:
+    def add(self: AT, key: Key | str, value: Any = ...) -> AT:
         ...
 
     def add(self, key, value=None):
diff --git a/tomlkit/parser.py b/tomlkit/parser.py
index 17e957bf..bdf0c4a2 100644
--- a/tomlkit/parser.py
+++ b/tomlkit/parser.py
@@ -60,7 +60,7 @@ class Parser:
     Parser for TOML documents.
     """
 
-    def __init__(self, string: str) -> None:
+    def __init__(self, string: str | bytes) -> None:
         # Input to parse
         self._src = Source(decode(string))
 
diff --git a/tomlkit/source.py b/tomlkit/source.py
index ab29854a..0e4db243 100644
--- a/tomlkit/source.py
+++ b/tomlkit/source.py
@@ -50,7 +50,7 @@ def __init__(self, source: Source) -> None:
     def __call__(self, *args, **kwargs):
         return _State(self._source, *args, **kwargs)
 
-    def __enter__(self) -> None:
+    def __enter__(self) -> _State:
         state = self()
         self._states.append(state)
         return state.__enter__()