diff --git a/.github/actions/setup-uv/action.yml b/.github/actions/setup-uv/action.yml
index a4f3f6d..5b2734e 100644
--- a/.github/actions/setup-uv/action.yml
+++ b/.github/actions/setup-uv/action.yml
@@ -3,8 +3,9 @@ runs:
   using: 'composite'
   steps:
     - name: Install uv
-      uses: astral-sh/setup-uv@v3
+      uses: astral-sh/setup-uv@v4
       with:
-        version: "0.5.1"
+        version: "0.5.10"
         enable-cache: true
         cache-dependency-glob: "**/pyproject.toml"
+        python-version: ${{ matrix.python-version }}
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 31b799e..43433d0 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -12,14 +12,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: [3.9, "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
 
     steps:
       - uses: actions/checkout@v4
       - name: Setup uv
+        # Installs Python based on ${{ matrix.python-version }}
         uses: ./.github/actions/setup-uv
-      - name: Set up Python ${{ matrix.python-version }}
-        run: uv python install ${{ matrix.python-version }}
       - name: Lint check
         run: make lint
       - name: Unit tests
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 5d5f10e..bb82585 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -1,6 +1,6 @@
 repos:
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.6.9
+    rev: v0.8.3
     hooks:
       - id: ruff
         args: [--fix, --exit-non-zero-on-fix]
@@ -13,7 +13,7 @@ repos:
       - id: end-of-file-fixer
       - id: trailing-whitespace
   - repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v1.12.0
+    rev: v1.13.0
     hooks:
       - id: mypy
         args: [--strict]
diff --git a/coqpit/coqpit.py b/coqpit/coqpit.py
index 60bd5b0..9d8866c 100644
--- a/coqpit/coqpit.py
+++ b/coqpit/coqpit.py
@@ -6,23 +6,16 @@
 import contextlib
 import json
 import operator
-import sys
 import typing
-from collections.abc import ItemsView, Iterable, Iterator, MutableMapping
+from collections.abc import Callable, ItemsView, Iterable, Iterator, MutableMapping
 from dataclasses import MISSING as _MISSING
 from dataclasses import Field, asdict, dataclass, fields, is_dataclass, replace
 from pathlib import Path
 from pprint import pprint
-from types import GenericAlias
-from typing import TYPE_CHECKING, Any, Callable, Generic, Literal, TypeVar, Union, overload
+from types import GenericAlias, UnionType
+from typing import TYPE_CHECKING, Any, Generic, Literal, TypeAlias, TypeGuard, TypeVar, Union, overload
 
-from typing_extensions import Self, TypeAlias, TypeGuard, TypeIs
-
-# TODO: Available from Python 3.10
-if sys.version_info >= (3, 10):
-    from types import UnionType
-else:
-    UnionType: TypeAlias = Union
+from typing_extensions import Self, TypeIs
 
 if TYPE_CHECKING:  # pragma: no cover
     import os
@@ -38,7 +31,7 @@ class _NoDefault(Generic[_T]):
     pass
 
 
-NoDefaultVar: TypeAlias = Union[_NoDefault[_T], _T]
+NoDefaultVar: TypeAlias = _NoDefault[_T] | _T
 no_default: NoDefaultVar[Any] = _NoDefault()
 
 FieldType: TypeAlias = Union[str, type, "UnionType"]
@@ -90,10 +83,7 @@ def _is_union(field_type: FieldType) -> TypeIs[UnionType]:
         bool: True if input type is `Union`
     """
     origin = typing.get_origin(field_type)
-    is_union = origin is Union
-    if sys.version_info >= (3, 10):
-        is_union = is_union or origin is UnionType
-    return is_union
+    return origin is Union or origin is UnionType
 
 
 def _is_union_and_not_simple_optional(field_type: FieldType) -> TypeGuard[UnionType]:
@@ -262,13 +252,13 @@ def _deserialize_primitive_types(
     Returns:
         Union[int, float, str, bool]: deserialized value.
     """
-    if isinstance(x, (str, bool)):
+    if isinstance(x, str | bool):
         return x
-    if isinstance(x, (int, float)):
+    if isinstance(x, int | float):
         base_type = _drop_none_type(field_type)
         if base_type is not float and base_type is not int and base_type is not str and base_type is not bool:
             raise TypeError
-        base_type = typing.cast(type[Union[int, float, str, bool]], base_type)
+        base_type = typing.cast(type[int | float | str | bool], base_type)
         if x == float("inf") or x == float("-inf"):
             # if value type is inf return regardless.
             return x
@@ -315,7 +305,7 @@ def _deserialize(x: Any, field_type: FieldType) -> Any:
 
 CoqpitType: TypeAlias = MutableMapping[str, "CoqpitNestedValue"]
 CoqpitNestedValue: TypeAlias = Union["CoqpitValue", CoqpitType]
-CoqpitValue: TypeAlias = Union[str, int, float, bool, None]
+CoqpitValue: TypeAlias = str | int | float | bool | None
 
 
 # TODO: It should be possible to get rid of the next 3 `type: ignore`. At
diff --git a/pyproject.toml b/pyproject.toml
index 479f7eb..b457ea5 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,10 +4,10 @@ build-backend = "hatchling.build"
 
 [project]
 name = "coqpit-config"
-version = "0.1.1"
+version = "0.1.2"
 description = "Simple (maybe too simple), light-weight config management through python data-classes."
 readme = "README.md"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 license = {text = "MIT"}
 authors = [
     {name = "Eren Gölge", email = "egolge@coqui.ai"}
@@ -18,7 +18,6 @@ maintainers = [
 classifiers = [
     "Programming Language :: Python",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
@@ -36,10 +35,10 @@ dependencies = [
 [dependency-groups]
 dev = [
     "coverage>=7",
-    "mypy>=1.12.0",
-    "pre-commit>=3",
+    "mypy>=1.13.0",
+    "pre-commit>=4",
     "pytest>=8",
-    "ruff==0.6.9",
+    "ruff==0.8.3",
 ]
 
 [project.urls]
@@ -59,7 +58,6 @@ exclude = [
 packages = ["coqpit"]
 
 [tool.ruff]
-target-version = "py39"
 line-length = 120
 lint.select = ["ALL"]
 lint.ignore = [
diff --git a/tests/test_init_from_dict.py b/tests/test_init_from_dict.py
index 1e0a735..67ebf90 100644
--- a/tests/test_init_from_dict.py
+++ b/tests/test_init_from_dict.py
@@ -1,5 +1,4 @@
 from dataclasses import dataclass, field
-from typing import Optional
 
 import pytest
 
@@ -8,8 +7,8 @@
 
 @dataclass
 class Person(Coqpit):
-    name: Optional[str] = None
-    age: Optional[int] = None
+    name: str | None = None
+    age: int | None = None
 
 
 @dataclass
diff --git a/tests/test_merge_configs.py b/tests/test_merge_configs.py
index f5e1ae4..b5c7673 100644
--- a/tests/test_merge_configs.py
+++ b/tests/test_merge_configs.py
@@ -1,5 +1,4 @@
 from dataclasses import dataclass
-from typing import Optional
 
 from coqpit.coqpit import Coqpit
 
@@ -7,7 +6,7 @@
 @dataclass
 class CoqpitA(Coqpit):
     val_a: int = 10
-    val_b: Optional[int] = None
+    val_b: int | None = None
     val_c: str = "Coqpit is great!"
     val_same: float = 10.21
 
@@ -23,7 +22,7 @@ class CoqpitB(Coqpit):
 @dataclass
 class Reference(Coqpit):
     val_a: int = 10
-    val_b: Optional[int] = None
+    val_b: int | None = None
     val_c: str = "Coqpit is great!"
     val_e: int = 257
     val_f: float = -10.21
diff --git a/tests/test_nested_configs.py b/tests/test_nested_configs.py
index 4117fe6..5707462 100644
--- a/tests/test_nested_configs.py
+++ b/tests/test_nested_configs.py
@@ -1,6 +1,5 @@
 from dataclasses import asdict, dataclass, field
 from pathlib import Path
-from typing import Optional, Union
 
 from coqpit import Coqpit, check_argument
 
@@ -8,7 +7,7 @@
 @dataclass
 class SimpleConfig(Coqpit):
     val_a: int = 10
-    val_b: Optional[int] = None
+    val_b: int | None = None
     val_c: str = "Coqpit is great!"
 
     def check_values(self) -> None:
@@ -22,11 +21,11 @@ def check_values(self) -> None:
 @dataclass
 class NestedConfig(Coqpit):
     val_d: int = 10
-    val_e: Optional[int] = None
+    val_e: int | None = None
     val_f: str = "Coqpit is great!"
-    sc_list: Optional[list[SimpleConfig]] = None
+    sc_list: list[SimpleConfig] | None = None
     sc: SimpleConfig = field(default_factory=lambda: SimpleConfig())
-    union_var: Union[list[SimpleConfig], SimpleConfig] = field(default_factory=lambda: [SimpleConfig(), SimpleConfig()])
+    union_var: list[SimpleConfig] | SimpleConfig = field(default_factory=lambda: [SimpleConfig(), SimpleConfig()])
 
     def check_values(self) -> None:
         """Check config fields"""
diff --git a/tests/test_parse_argparse.py b/tests/test_parse_argparse.py
index ec7d137..c0f843b 100644
--- a/tests/test_parse_argparse.py
+++ b/tests/test_parse_argparse.py
@@ -1,18 +1,17 @@
 from dataclasses import asdict, dataclass, field
-from typing import Optional
 
 from coqpit.coqpit import Coqpit, check_argument
 
 
 @dataclass
 class SimplerConfig(Coqpit):
-    val_a: Optional[int] = field(default=None, metadata={"help": "this is val_a"})
+    val_a: int | None = field(default=None, metadata={"help": "this is val_a"})
 
 
 @dataclass
 class SimpleConfig(Coqpit):
     val_a: int = field(default=10, metadata={"help": "this is val_a of SimpleConfig"})
-    val_b: Optional[int] = field(default=None, metadata={"help": "this is val_b"})
+    val_b: int | None = field(default=None, metadata={"help": "this is val_b"})
     val_c: str = "Coqpit is great!"
     val_dict: dict[str, int] = field(default_factory=lambda: {"val_a": 100, "val_b": 200, "val_c": 300})
     mylist_with_default: list[SimplerConfig] = field(
@@ -21,8 +20,8 @@ class SimpleConfig(Coqpit):
     )
     int_list: list[int] = field(default_factory=lambda: [1, 2, 3], metadata={"help": "int"})
     str_list: list[str] = field(default_factory=lambda: ["veni", "vidi", "vici"], metadata={"help": "str"})
-    empty_int_list: Optional[list[int]] = field(default=None, metadata={"help": "int list without default value"})
-    empty_str_list: Optional[list[str]] = field(default=None, metadata={"help": "str list without default value"})
+    empty_int_list: list[int] | None = field(default=None, metadata={"help": "int list without default value"})
+    empty_str_list: list[str] | None = field(default=None, metadata={"help": "str list without default value"})
     list_with_default_factory: list[str] = field(
         default_factory=list,
         metadata={"help": "str list with default factory"},
@@ -140,13 +139,13 @@ def test_argparse_with_required_field() -> None:
 def test_init_argparse_list_and_nested() -> None:
     @dataclass
     class SimplerConfig2(Coqpit):
-        val_a: Optional[int] = field(default=None, metadata={"help": "this is val_a"})
+        val_a: int | None = field(default=None, metadata={"help": "this is val_a"})
 
     @dataclass
     class SimpleConfig2(Coqpit):
         val_req: str  # required field
         val_a: int = field(default=10, metadata={"help": "this is val_a of SimpleConfig2"})
-        val_b: Optional[int] = field(default=None, metadata={"help": "this is val_b"})
+        val_b: int | None = field(default=None, metadata={"help": "this is val_b"})
         nested_config: SimplerConfig2 = field(default_factory=lambda: SimplerConfig2())
         mylist_with_default: list[SimplerConfig2] = field(
             default_factory=lambda: [SimplerConfig2(val_a=100), SimplerConfig2(val_a=999)],
diff --git a/tests/test_parse_known_argparse.py b/tests/test_parse_known_argparse.py
index a1b3218..5ca5142 100644
--- a/tests/test_parse_known_argparse.py
+++ b/tests/test_parse_known_argparse.py
@@ -1,18 +1,17 @@
 from dataclasses import asdict, dataclass, field
-from typing import Optional
 
 from coqpit.coqpit import Coqpit, check_argument
 
 
 @dataclass
 class SimplerConfig(Coqpit):
-    val_a: Optional[int] = field(default=None, metadata={"help": "this is val_a"})
+    val_a: int | None = field(default=None, metadata={"help": "this is val_a"})
 
 
 @dataclass
 class SimpleConfig(Coqpit):
     val_a: int = field(default=10, metadata={"help": "this is val_a of SimpleConfig"})
-    val_b: Optional[int] = field(default=None, metadata={"help": "this is val_b"})
+    val_b: int | None = field(default=None, metadata={"help": "this is val_b"})
     val_c: str = "Coqpit is great!"
     mylist_with_default: list[SimplerConfig] = field(
         default_factory=lambda: [SimplerConfig(val_a=100), SimplerConfig(val_a=999)],
diff --git a/tests/test_relaxed_parse_known_argparse.py b/tests/test_relaxed_parse_known_argparse.py
index 9d096b2..0365fa7 100644
--- a/tests/test_relaxed_parse_known_argparse.py
+++ b/tests/test_relaxed_parse_known_argparse.py
@@ -1,5 +1,5 @@
 from dataclasses import asdict, dataclass, field
-from typing import Any, Optional, Union
+from typing import Any
 
 from coqpit.coqpit import Coqpit, check_argument
 
@@ -7,9 +7,9 @@
 @dataclass
 class SimpleConfig(Coqpit):
     val_a: int = field(default=10, metadata={"help": "this is val_a of SimpleConfig"})
-    val_b: Optional[int] = field(default=None, metadata={"help": "this is val_b"})
-    val_c: Optional[Union[int, str]] = None
-    val_d: Optional[list[list[Any]]] = None
+    val_b: int | None = field(default=None, metadata={"help": "this is val_b"})
+    val_c: int | str | None = None
+    val_d: list[list[Any]] | None = None
 
     def check_values(self) -> None:
         """Check config fields"""
diff --git a/tests/test_serialization.py b/tests/test_serialization.py
index 9cd7d2b..4470c60 100644
--- a/tests/test_serialization.py
+++ b/tests/test_serialization.py
@@ -1,6 +1,5 @@
 from dataclasses import dataclass, field
 from pathlib import Path
-from typing import Optional, Union
 
 import pytest
 
@@ -9,23 +8,23 @@
 
 @dataclass
 class Person(Coqpit):
-    name: Optional[str] = None
-    age: Optional[int] = None
+    name: str | None = None
+    age: int | None = None
 
 
 @dataclass
 class Group(Coqpit):
-    name: Optional[str] = None
-    size: Optional[int] = None
-    path: Optional[Path] = None
+    name: str | None = None
+    size: int | None = None
+    path: Path | None = None
     people: list[Person] = field(default_factory=list)
-    some_dict: dict[str, Optional[int]] = field(default_factory=dict)
+    some_dict: dict[str, int | None] = field(default_factory=dict)
 
 
 @dataclass
 class Reference(Coqpit):
-    name: Optional[str] = "Coqpit"
-    size: Optional[int] = 3
+    name: str | None = "Coqpit"
+    size: int | None = 3
     path: Path = Path("a/b")
     people: list[Person] = field(
         default_factory=lambda: [
@@ -34,7 +33,7 @@ class Reference(Coqpit):
             Person(name="Ceren", age=15),
         ],
     )
-    some_dict: dict[str, Optional[int]] = field(default_factory=lambda: {"a": 1, "b": 2, "c": None})
+    some_dict: dict[str, int | None] = field(default_factory=lambda: {"a": 1, "b": 2, "c": None})
 
 
 def test_serialization() -> None:
@@ -70,8 +69,6 @@ def test_deserialize_list() -> None:
     assert _deserialize_list([1, 2, 3], list[str]) == ["1", "2", "3"]
 
 
-# TODO: `type: ignore` can probably be removed when switching to Python 3.10
-#       Union syntax (e.g. str | int)
 def test_deserialize_primitive_type() -> None:
     cases = (
         (True, bool, True),
@@ -83,21 +80,21 @@ def test_deserialize_primitive_type() -> None:
         (3, str, "3"),
         (3.0, str, "3.0"),
         (3, bool, True),
-        ("a", Union[str, None], "a"),
-        ("3", Union[str, None], "3"),
-        (3, Union[int, None], 3),
-        (3, Union[float, None], 3.0),
-        (None, Union[str, None], None),
-        (None, Union[int, None], None),
-        (None, Union[float, None], None),
-        (None, Union[str, None], None),
+        ("a", str | None, "a"),
+        ("3", str | None, "3"),
+        (3, int | None, 3),
+        (3, float | None, 3.0),
+        (None, str | None, None),
+        (None, int | None, None),
+        (None, float | None, None),
+        (None, str | None, None),
         (float("inf"), float, float("inf")),
         (float("inf"), int, float("inf")),
         (float("-inf"), float, float("-inf")),
         (float("-inf"), int, float("-inf")),
     )
     for value, field_type, expected in cases:
-        assert _deserialize_primitive_types(value, field_type) == expected  # type: ignore[arg-type]
+        assert _deserialize_primitive_types(value, field_type) == expected
 
     with pytest.raises(TypeError):
         _deserialize_primitive_types(3, Coqpit)
diff --git a/tests/test_simple_config.py b/tests/test_simple_config.py
index cc2d17a..f74e7ec 100644
--- a/tests/test_simple_config.py
+++ b/tests/test_simple_config.py
@@ -1,6 +1,6 @@
 from dataclasses import asdict, dataclass, field
 from pathlib import Path
-from typing import Any, Optional, Union
+from typing import Any
 
 from coqpit.coqpit import MISSING, Coqpit, check_argument
 
@@ -8,7 +8,7 @@
 @dataclass
 class SimpleConfig(Coqpit):
     val_a: int = 10
-    val_b: Optional[int] = None
+    val_b: int | None = None
     val_d: float = 10.21
     val_c: str = "Coqpit is great!"
     vol_e: bool = True
@@ -19,7 +19,7 @@ class SimpleConfig(Coqpit):
     val_dict: dict[str, Any] = field(default_factory=lambda: {"val_aa": 10, "val_ss": "This is in a dict."})
     # list of list
     val_listoflist: list[list[int]] = field(default_factory=lambda: [[1, 2], [3, 4]])
-    val_listofunion: list[list[Union[str, int, bool]]] = field(
+    val_listofunion: list[list[str | int | bool]] = field(
         default_factory=lambda: [[1, 3], [1, "Hi!"], [True, False]],
     )
 
diff --git a/tests/test_utils.py b/tests/test_utils.py
index 7d7de34..6e44a11 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -1,44 +1,39 @@
-from typing import Union
-
 from coqpit.coqpit import _is_optional_field, _is_union, _is_union_and_not_simple_optional
 
-# TODO: `type: ignore` can probably be removed when switching to Python 3.10
-#       Union syntax (e.g. str | int)
-
 
 def test_is_union() -> None:
     cases = (
-        (Union[str, int], True),
-        (Union[str, None], True),
+        (str | int, True),
+        (str | None, True),
         (int, False),
         (list[int], False),
-        (list[Union[str, int]], False),
+        (list[str | int], False),
     )
     for item, expected in cases:
-        assert _is_union(item) == expected  # type: ignore[arg-type]
+        assert _is_union(item) == expected
 
 
 def test_is_union_and_not_simple_optional() -> None:
     cases = (
-        (Union[str, int], True),
-        (Union[str, None], False),
-        (Union[list[int], None], False),
+        (str | int, True),
+        (str | None, False),
+        (list[int] | None, False),
         (int, False),
         (list[int], False),
-        (list[Union[str, int]], False),
+        (list[str | int], False),
     )
     for item, expected in cases:
-        assert _is_union_and_not_simple_optional(item) == expected  # type: ignore[arg-type]
+        assert _is_union_and_not_simple_optional(item) == expected
 
 
 def test_is_optional_field() -> None:
     cases = (
-        (Union[str, int], False),
-        (Union[str, None], True),
-        (Union[list[int], None], True),
+        (str | int, False),
+        (str | None, True),
+        (list[int] | None, True),
         (int, False),
         (list[int], False),
-        (list[Union[str, int]], False),
+        (list[str | int], False),
     )
     for item, expected in cases:
-        assert _is_optional_field(item) == expected  # type: ignore[arg-type]
+        assert _is_optional_field(item) == expected