diff --git a/webdriver/tests/bidi/emulation/set_locale_override/conftest.py b/webdriver/tests/bidi/emulation/set_locale_override/conftest.py
index e687010128a470..99560e70ac53a2 100644
--- a/webdriver/tests/bidi/emulation/set_locale_override/conftest.py
+++ b/webdriver/tests/bidi/emulation/set_locale_override/conftest.py
@@ -55,3 +55,102 @@ def another_locale(default_locale, some_locale):
     raise Exception(
         f"Unexpectedly could not find locale different from the default {default_locale} and {some_locale}"
     )
+
+
+@pytest_asyncio.fixture
+async def get_current_navigator_language(bidi_session):
+    async def get_current_navigator_language(context, sandbox=None):
+        result = await bidi_session.script.evaluate(
+            expression="navigator.language",
+            target=ContextTarget(context["context"], sandbox=sandbox),
+            await_promise=False,
+        )
+
+        return result["value"]
+
+    return get_current_navigator_language
+
+
+@pytest_asyncio.fixture
+async def default_navigator_language(get_current_navigator_language, top_context):
+    """Returns default navigator.language value."""
+    return await get_current_navigator_language(top_context)
+
+
+@pytest_asyncio.fixture
+async def get_current_navigator_languages(bidi_session):
+    async def get_current_navigator_languages(context, sandbox=None):
+        result = await bidi_session.script.evaluate(
+            expression="navigator.languages",
+            target=ContextTarget(context["context"], sandbox=sandbox),
+            await_promise=False,
+        )
+
+        return [item["value"] for item in result["value"]]
+
+    return get_current_navigator_languages
+
+
+@pytest_asyncio.fixture
+async def default_navigator_languages(get_current_navigator_languages, top_context):
+    """Returns default navigator.languages value."""
+    return await get_current_navigator_languages(top_context)
+
+
+@pytest_asyncio.fixture
+async def assert_locale_against_default(
+    top_context,
+    get_current_locale,
+    get_current_navigator_language,
+    get_current_navigator_languages,
+    default_locale,
+    default_navigator_language,
+    default_navigator_languages,
+):
+    """
+    Assert JS locale and navigator.language/s against default values.
+
+    Note: it's possible to have slightly different values between JS locale and
+    navigator.language/s, that's why we have to retrieve the default values
+    for each API.
+    """
+
+    async def assert_locale_against_default(context, sandbox_name=None):
+        assert (
+            context != top_context
+        ), "Provided context should be different from top_context"
+
+        assert await get_current_locale(context, sandbox_name) == default_locale
+        assert (
+            await get_current_navigator_language(context, sandbox_name)
+            == default_navigator_language
+        )
+        assert (
+            await get_current_navigator_languages(context, sandbox_name)
+            == default_navigator_languages
+        )
+
+    return assert_locale_against_default
+
+
+@pytest_asyncio.fixture
+async def assert_locale_against_value(
+    top_context,
+    get_current_locale,
+    get_current_navigator_language,
+    get_current_navigator_languages,
+):
+    """
+    Assert JS locale and navigator.language/s against provided value
+    """
+
+    async def assert_locale_against_value(value, context, sandbox_name=None):
+        assert (
+            context != top_context
+        ), "Provided context should be different from top_context"
+
+        assert await get_current_locale(context, sandbox_name) == value
+        assert await get_current_navigator_language(context, sandbox_name) == value
+        assert await get_current_navigator_languages(context, sandbox_name) == [value]
+
+    return assert_locale_against_value
diff --git a/webdriver/tests/bidi/emulation/set_locale_override/contexts.py b/webdriver/tests/bidi/emulation/set_locale_override/contexts.py
index b2a2ceaecae316..3e60adb4cd75d3 100644
--- a/webdriver/tests/bidi/emulation/set_locale_override/contexts.py
+++ b/webdriver/tests/bidi/emulation/set_locale_override/contexts.py
@@ -1,64 +1,73 @@
 import pytest
-from webdriver.bidi.modules.script import ContextTarget
 
 pytestmark = pytest.mark.asyncio
 
 
-async def test_contexts(bidi_session, new_tab, top_context, get_current_locale,
-        default_locale, some_locale):
+async def test_contexts(
+    bidi_session,
+    new_tab,
+    some_locale,
+    assert_locale_against_default,
+    assert_locale_against_value,
+):
+    new_context = await bidi_session.browsing_context.create(type_hint="tab")
+
     # Set locale override.
     await bidi_session.emulation.set_locale_override(
-        contexts=[new_tab["context"]],
-        locale=some_locale
+        contexts=[new_tab["context"]], locale=some_locale
     )
 
     # Assert locale emulated only in the required context.
-    assert await get_current_locale(new_tab) == some_locale
-    assert await get_current_locale(top_context) == default_locale
+    await assert_locale_against_value(some_locale, new_tab)
+    await assert_locale_against_default(new_context)
 
     # Reset locale override.
     await bidi_session.emulation.set_locale_override(
-        contexts=[new_tab["context"]],
-        locale=None)
+        contexts=[new_tab["context"]], locale=None
+    )
 
     # Assert the locale is restored to the initial one.
-    assert await get_current_locale(new_tab) == default_locale
-    assert await get_current_locale(top_context) == default_locale
+    await assert_locale_against_default(new_tab)
+    await assert_locale_against_default(new_context)
 
 
-async def test_multiple_contexts(bidi_session, new_tab, get_current_locale,
-        default_locale, some_locale):
+async def test_multiple_contexts(
+    bidi_session,
+    new_tab,
+    assert_locale_against_value,
+    assert_locale_against_default,
+    some_locale,
+):
     new_context = await bidi_session.browsing_context.create(type_hint="tab")
 
     # Set locale override.
     await bidi_session.emulation.set_locale_override(
-        contexts=[new_tab["context"], new_context["context"]],
-        locale=some_locale
+        contexts=[new_tab["context"], new_context["context"]], locale=some_locale
     )
 
     # Assert locale emulated in all the required contexts.
-    assert await get_current_locale(new_tab) == some_locale
-    assert await get_current_locale(new_context) == some_locale
+    await assert_locale_against_value(some_locale, new_tab)
+    await assert_locale_against_value(some_locale, new_context)
 
     # Reset locale override.
     await bidi_session.emulation.set_locale_override(
-        contexts=[new_tab["context"], new_context["context"]],
-        locale=None)
+        contexts=[new_tab["context"], new_context["context"]], locale=None
+    )
 
     # Assert the locale is restored to the initial one.
-    assert await get_current_locale(new_tab) == default_locale
-    assert await get_current_locale(new_context) == default_locale
+    await assert_locale_against_default(new_tab)
+    await assert_locale_against_default(new_context)
 
 
 @pytest.mark.parametrize("domain", ["", "alt"], ids=["same_origin", "cross_origin"])
 async def test_iframe(
     bidi_session,
     new_tab,
-    get_current_locale,
     some_locale,
     domain,
     inline,
     another_locale,
+    assert_locale_against_value,
 ):
     # Set locale override.
     await bidi_session.emulation.set_locale_override(
@@ -66,7 +75,7 @@ async def test_iframe(
     )
 
     # Assert locale emulated in the required context.
-    assert await get_current_locale(new_tab) == some_locale
+    await assert_locale_against_value(some_locale, new_tab)
 
     iframe_url = inline("<div id='in-iframe'>foo</div>", domain=domain)
     page_url = inline(f"<iframe src='{iframe_url}'></iframe>")
@@ -82,11 +91,11 @@ async def test_iframe(
     iframe = contexts[0]["children"][0]
 
     # Assert locale is emulated in the iframe context.
-    assert await get_current_locale(iframe) == some_locale
+    await assert_locale_against_value(some_locale, iframe)
 
     sandbox_name = "test"
     # Assert locale is emulated in the newly created sandbox in the iframe context.
-    assert await get_current_locale(iframe, sandbox_name) == some_locale
+    await assert_locale_against_value(some_locale, iframe, sandbox_name)
 
     # Set another locale override.
     await bidi_session.emulation.set_locale_override(
@@ -94,33 +103,37 @@ async def test_iframe(
     )
 
     # Assert locale is emulated in the iframe context.
-    assert await get_current_locale(iframe) == another_locale
+    await assert_locale_against_value(another_locale, iframe)
     # Assert locale is emulated in the existing sandbox in the iframe context.
-    assert await get_current_locale(iframe, sandbox_name) == another_locale
+    await assert_locale_against_value(another_locale, iframe, sandbox_name)
 
 
 async def test_locale_override_applies_to_new_sandbox(
-    bidi_session, new_tab, some_locale, get_current_locale
+    bidi_session, new_tab, some_locale, assert_locale_against_value
 ):
     await bidi_session.emulation.set_locale_override(
         contexts=[new_tab["context"]], locale=some_locale
     )
 
     # Make sure the override got applied to the newly created sandbox.
-    assert await get_current_locale(new_tab, "test") == some_locale
+    await assert_locale_against_value(some_locale, new_tab, "test")
 
 
 async def test_locale_override_applies_to_existing_sandbox(
-    bidi_session, new_tab, default_locale, another_locale, get_current_locale
+    bidi_session,
+    new_tab,
+    another_locale,
+    assert_locale_against_value,
+    assert_locale_against_default,
 ):
     sandbox_name = "test"
 
     # Create a sandbox.
-    assert await get_current_locale(new_tab, sandbox_name) == default_locale
+    await assert_locale_against_default(new_tab, sandbox_name)
 
     await bidi_session.emulation.set_locale_override(
         contexts=[new_tab["context"]], locale=another_locale
     )
 
     # Make sure the override got applied to the existing sandbox.
-    assert await get_current_locale(new_tab, sandbox_name) == another_locale
+    await assert_locale_against_value(another_locale, new_tab, sandbox_name)
diff --git a/webdriver/tests/bidi/emulation/set_locale_override/locale.py b/webdriver/tests/bidi/emulation/set_locale_override/locale.py
index 3da7f62f520082..c7ea1473b9ca49 100644
--- a/webdriver/tests/bidi/emulation/set_locale_override/locale.py
+++ b/webdriver/tests/bidi/emulation/set_locale_override/locale.py
@@ -3,79 +3,96 @@
 pytestmark = pytest.mark.asyncio
 
 
-async def test_locale_set_override_and_reset(bidi_session, top_context,
-        get_current_locale, default_locale, some_locale, another_locale):
-    assert await get_current_locale(top_context) == default_locale
+async def test_locale_set_override_and_reset(
+    bidi_session,
+    new_tab,
+    some_locale,
+    another_locale,
+    assert_locale_against_default,
+    assert_locale_against_value,
+):
+    await assert_locale_against_default(new_tab)
 
     # Set locale override.
     await bidi_session.emulation.set_locale_override(
-        contexts=[top_context["context"]],
-        locale=some_locale
+        contexts=[new_tab["context"]], locale=some_locale
     )
 
-    assert await get_current_locale(top_context) == some_locale
+    await assert_locale_against_value(some_locale, new_tab)
 
-    # Set locale override.
+    # Set another locale override.
     await bidi_session.emulation.set_locale_override(
-        contexts=[top_context["context"]],
-        locale=another_locale
+        contexts=[new_tab["context"]], locale=another_locale
     )
 
-    assert await get_current_locale(top_context) == another_locale
+    await assert_locale_against_value(another_locale, new_tab)
 
-    # Set locale override.
+    # Reset locale override.
     await bidi_session.emulation.set_locale_override(
-        contexts=[top_context["context"]],
-        locale=None
+        contexts=[new_tab["context"]], locale=None
     )
 
-    assert await get_current_locale(top_context) == default_locale
-
-
-@pytest.mark.parametrize("value", [
-    # Simple language code (2-letter).
-    "en",
-    # Language and region (both 2-letter).
-    "en-US",
-    # Language and script (4-letter).
-    "sr-Latn",
-    # Language, script, and region.
-    "zh-Hans-CN",
-])
-async def test_locale_values(bidi_session, top_context, get_current_locale,
-        default_locale, value):
-    assert await get_current_locale(top_context) == default_locale
+    await assert_locale_against_default(new_tab)
+
+
+@pytest.mark.parametrize(
+    "value",
+    [
+        # Simple language code (2-letter).
+        "en",
+        # Language and region (both 2-letter).
+        "en-US",
+        # Language and script (4-letter).
+        "sr-Latn",
+        # Language, script, and region.
+        "zh-Hans-CN",
+    ],
+)
+async def test_locale_values(
+    bidi_session,
+    new_tab,
+    assert_locale_against_default,
+    assert_locale_against_value,
+    value,
+):
+    await assert_locale_against_default(new_tab)
 
     # Set locale override.
     await bidi_session.emulation.set_locale_override(
-        contexts=[top_context["context"]],
-        locale=value
+        contexts=[new_tab["context"]], locale=value
     )
 
-    assert await get_current_locale(top_context) == value
-
-
-@pytest.mark.parametrize("locale,expected_locale", [
-    # Locale with Unicode extension keyword for collation.
-    ("de-DE-u-co-phonebk", "de-DE"),
-    # Lowercase language and region.
-    ("fr-ca", "fr-CA"),
-    # Uppercase language and region (should be normalized by Intl.Locale).
-    ("FR-CA", "fr-CA"),
-    # Mixed case language and region (should be normalized by Intl.Locale).
-    ("fR-cA", "fr-CA"),
-    # Locale with transform extension (simple case).
-    ("en-t-zh", "en"),
-])
-async def test_locale_values_normalized_by_intl(bidi_session, top_context,
-        get_current_locale,
-        default_locale, locale, expected_locale):
+    await assert_locale_against_value(value, new_tab)
+
+
+@pytest.mark.parametrize(
+    "locale,expected_locale",
+    [
+        # Locale with Unicode extension keyword for collation.
+        ("de-DE-u-co-phonebk", "de-DE"),
+        # Lowercase language and region.
+        ("fr-ca", "fr-CA"),
+        # Uppercase language and region (should be normalized by Intl.Locale).
+        ("FR-CA", "fr-CA"),
+        # Mixed case language and region (should be normalized by Intl.Locale).
+        ("fR-cA", "fr-CA"),
+        # Locale with transform extension (simple case).
+        ("en-t-zh", "en"),
+    ],
+)
+async def test_locale_values_normalized_by_intl(
+    bidi_session,
+    top_context,
+    get_current_locale,
+    default_locale,
+    locale,
+    expected_locale,
+):
     assert await get_current_locale(top_context) == default_locale
 
     # Set locale override.
     await bidi_session.emulation.set_locale_override(
-        contexts=[top_context["context"]],
-        locale=locale
+        contexts=[top_context["context"]], locale=locale
     )
 
     assert await get_current_locale(top_context) == expected_locale
diff --git a/webdriver/tests/bidi/emulation/set_locale_override/user_contexts.py b/webdriver/tests/bidi/emulation/set_locale_override/user_contexts.py
index 525dec61093ca7..fec2fc745f41cc 100644
--- a/webdriver/tests/bidi/emulation/set_locale_override/user_contexts.py
+++ b/webdriver/tests/bidi/emulation/set_locale_override/user_contexts.py
@@ -4,45 +4,46 @@
 
 
 async def test_user_contexts(
-        bidi_session,
-        create_user_context,
-        new_tab,
-        get_current_locale,
-        default_locale,
-        some_locale
+    bidi_session,
+    create_user_context,
+    new_tab,
+    some_locale,
+    assert_locale_against_default,
+    assert_locale_against_value,
 ):
     user_context = await create_user_context()
     context_in_user_context = await bidi_session.browsing_context.create(
-        user_context=user_context, type_hint="tab")
+        user_context=user_context, type_hint="tab"
+    )
 
-    assert await get_current_locale(new_tab) == default_locale
+    await assert_locale_against_default(new_tab)
 
     # Set locale override.
     await bidi_session.emulation.set_locale_override(
-        user_contexts=[user_context],
-        locale=some_locale)
+        user_contexts=[user_context], locale=some_locale
+    )
 
     # Assert the locale is emulated in user context.
-    assert await get_current_locale(context_in_user_context) == some_locale
+    await assert_locale_against_value(some_locale, context_in_user_context)
 
     # Assert the default user context is not affected.
-    assert await get_current_locale(new_tab) == default_locale
+    await assert_locale_against_default(new_tab)
 
     # Create a new context in the user context.
     another_context_in_user_context = await bidi_session.browsing_context.create(
-        user_context=user_context, type_hint="tab")
+        user_context=user_context, type_hint="tab"
+    )
     # Assert the locale is emulated in a new browsing context of the user context.
-    assert await get_current_locale(
-        another_context_in_user_context) == some_locale
+    await assert_locale_against_value(some_locale, another_context_in_user_context)
 
 
 async def test_set_to_default_user_context(
-        bidi_session,
-        new_tab,
-        create_user_context,
-        get_current_locale,
-        default_locale,
-        some_locale
+    bidi_session,
+    new_tab,
+    create_user_context,
+    some_locale,
+    assert_locale_against_default,
+    assert_locale_against_value,
 ):
     user_context = await create_user_context()
     context_in_user_context = await bidi_session.browsing_context.create(
@@ -56,29 +57,27 @@ async def test_set_to_default_user_context(
 
     # Make sure that the locale changes are only applied to the context
     # associated with default user context.
-    assert await get_current_locale(context_in_user_context) == default_locale
-    assert await get_current_locale(new_tab) == some_locale
+    await assert_locale_against_default(context_in_user_context)
+    await assert_locale_against_value(some_locale, new_tab)
 
     # Create a new context in the default context.
     context_in_default_context = await bidi_session.browsing_context.create(
         type_hint="tab"
     )
 
-    assert await get_current_locale(context_in_default_context) == some_locale
-    assert await get_current_locale(context_in_default_context) == some_locale
+    await assert_locale_against_value(some_locale, context_in_default_context)
 
     # Reset locale override.
     await bidi_session.emulation.set_locale_override(
-        user_contexts=["default"],
-        locale=None
+        user_contexts=["default"], locale=None
     )
 
 
 async def test_set_to_multiple_user_contexts(
-        bidi_session,
-        create_user_context,
-        get_current_locale,
-        some_locale,
+    bidi_session,
+    create_user_context,
+    some_locale,
+    assert_locale_against_value,
 ):
     user_context_1 = await create_user_context()
     context_in_user_context_1 = await bidi_session.browsing_context.create(
@@ -89,21 +88,20 @@ async def test_set_to_multiple_user_contexts(
         user_context=user_context_2, type_hint="tab"
     )
     await bidi_session.emulation.set_locale_override(
-        user_contexts=[user_context_1, user_context_2],
-        locale=some_locale
+        user_contexts=[user_context_1, user_context_2], locale=some_locale
     )
 
-    assert await get_current_locale(context_in_user_context_1) == some_locale
-    assert await get_current_locale(context_in_user_context_2) == some_locale
+    await assert_locale_against_value(some_locale, context_in_user_context_1)
+    await assert_locale_against_value(some_locale, context_in_user_context_2)
 
 
 async def test_set_to_user_context_and_then_to_context(
-        bidi_session,
-        create_user_context,
-        get_current_locale,
-        default_locale,
-        some_locale,
-        another_locale
+    bidi_session,
+    create_user_context,
+    some_locale,
+    another_locale,
+    assert_locale_against_default,
+    assert_locale_against_value,
 ):
     user_context = await create_user_context()
     context_in_user_context_1 = await bidi_session.browsing_context.create(
@@ -112,30 +110,28 @@ async def test_set_to_user_context_and_then_to_context(
 
     # Apply locale override to the user context.
     await bidi_session.emulation.set_locale_override(
-        user_contexts=[user_context],
-        locale=some_locale
+        user_contexts=[user_context], locale=some_locale
     )
 
     # Apply locale override now only to the context.
     await bidi_session.emulation.set_locale_override(
-        contexts=[context_in_user_context_1["context"]],
-        locale=another_locale
+        contexts=[context_in_user_context_1["context"]], locale=another_locale
     )
-    assert await get_current_locale(context_in_user_context_1) == another_locale
+    await assert_locale_against_value(another_locale, context_in_user_context_1)
 
     await bidi_session.browsing_context.reload(
         context=context_in_user_context_1["context"], wait="complete"
     )
 
     # Make sure that after reload the locale is still updated.
-    assert await get_current_locale(context_in_user_context_1) == another_locale
+    await assert_locale_against_value(another_locale, context_in_user_context_1)
 
     # Create a new context in the user context.
     context_in_user_context_2 = await bidi_session.browsing_context.create(
         user_context=user_context, type_hint="tab"
     )
     # Make sure that the locale override for the user context is applied.
-    assert await get_current_locale(context_in_user_context_2) == some_locale
+    await assert_locale_against_value(some_locale, context_in_user_context_2)
 
     # Reset the override for context.
     await bidi_session.emulation.set_locale_override(
@@ -144,7 +140,7 @@ async def test_set_to_user_context_and_then_to_context(
     )
 
     # Make sure that the locale override is set to user context value.
-    assert await get_current_locale(context_in_user_context_1) == some_locale
+    await assert_locale_against_value(some_locale, context_in_user_context_1)
 
     # Reset the override for user context.
     await bidi_session.emulation.set_locale_override(
@@ -153,16 +149,16 @@ async def test_set_to_user_context_and_then_to_context(
     )
 
     # Make sure that the locale override is reset.
-    assert await get_current_locale(context_in_user_context_1) == default_locale
+    await assert_locale_against_default(context_in_user_context_1)
 
 
 async def test_set_to_context_and_then_to_user_context(
     bidi_session,
     create_user_context,
-    get_current_locale,
-    default_locale,
     some_locale,
-    another_locale
+    another_locale,
+    assert_locale_against_default,
+    assert_locale_against_value,
 ):
     user_context = await create_user_context()
     context_in_user_context_1 = await bidi_session.browsing_context.create(
@@ -174,7 +170,7 @@ async def test_set_to_context_and_then_to_user_context(
         contexts=[context_in_user_context_1["context"]], locale=some_locale
     )
 
-    assert await get_current_locale(context_in_user_context_1) == some_locale
+    await assert_locale_against_value(some_locale, context_in_user_context_1)
 
     # Apply locale override to the user context.
     await bidi_session.emulation.set_locale_override(
@@ -182,21 +178,21 @@ async def test_set_to_context_and_then_to_user_context(
     )
 
     # Make sure that context has still the context locale override.
-    assert await get_current_locale(context_in_user_context_1) == some_locale
+    await assert_locale_against_value(some_locale, context_in_user_context_1)
 
     await bidi_session.browsing_context.reload(
         context=context_in_user_context_1["context"], wait="complete"
     )
 
     # Make sure that after reload the locale still has the context locale override.
-    assert await get_current_locale(context_in_user_context_1) == some_locale
+    await assert_locale_against_value(some_locale, context_in_user_context_1)
 
     # Create a new context in the user context.
     context_in_user_context_2 = await bidi_session.browsing_context.create(
         user_context=user_context, type_hint="tab"
     )
     # Make sure that the locale override for the user context is applied.
-    assert await get_current_locale(context_in_user_context_2) == another_locale
+    await assert_locale_against_value(another_locale, context_in_user_context_2)
 
     # Reset override for user context.
     await bidi_session.emulation.set_locale_override(
@@ -205,6 +201,6 @@ async def test_set_to_context_and_then_to_user_context(
     )
 
     # Make sure that the locale override for the first context is still set.
-    assert await get_current_locale(context_in_user_context_1) == some_locale
+    await assert_locale_against_value(some_locale, context_in_user_context_1)
     # Make sure that the locale override for the second context is reset.
-    assert await get_current_locale(context_in_user_context_2) == default_locale
+    await assert_locale_against_default(context_in_user_context_2)