diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index b23fc68345..051f01dfe2 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -99,7 +99,7 @@ Changelog
  * Fix: Make sure the focus outline of checkboxes is fully around the outer border (Steven Steinwand)
  * Fix: Consistently set `aria-haspopup="menu"` for all sidebar menu items that have sub-menus (LB (Ben Johnston))
  * Fix: Make sure `aria-expanded` is always explicitly set as a string in sidebar (LB (Ben Johnston))
- * Fix: Use a button element instead of a link for page explorer menu item, for the correct semantics and behavior (LB (Ben Johnston))
+ * Fix: Use a button element instead of a link for page explorer menu item, for the correct semantics and behaviour (LB (Ben Johnston))
  * Fix: Make sure the “Title” column label can be translated in the page chooser and page move UI (Stephanie Cheng Smith)
  * Fix: Remove redundant `role="main"` attributes on `<main>` elements causing HTML validation issues (Luis Espinoza)
  * Fix: Allow bulk publishing of pages without revisions (Andy Chosak)
@@ -844,7 +844,7 @@ Changelog
  * Removed support for Django 2.0
  * Removed leftover Python 2.x compatibility code (Sergey Fedoseev)
  * Combine flake8 configurations (Sergey Fedoseev)
- * Improve diffing behavior for text fields (Aliosha Padovani)
+ * Improve diffing behaviour for text fields (Aliosha Padovani)
  * Improve contrast of disabled inputs (Nick Smith)
  * Added `get_document_model_string` function (Andrey Smirnov)
  * Added support for Cloudflare API tokens for frontend cache invalidation (Tom Usher)
@@ -994,7 +994,7 @@ Changelog
  * Updated group edit view to expose the Permission object for each checkbox (George Hickman)
  * Improve performance of Pages for Moderation panel (Fidel Ramos)
  * Add more contextual information for screen readers in the explorer menu’s links (Helen Chapman)
- * Added `process_child_object` and `exclude_fields` arguments to ``Page.copy()`` to make it easier for third-party apps to customise copy behavior (Karl Hobley)
+ * Added `process_child_object` and `exclude_fields` arguments to ``Page.copy()`` to make it easier for third-party apps to customise copy behaviour (Karl Hobley)
  * Added `Page.with_content_json()`, allowing revision content loading behaviour to be customised on a per-model basis (Karl Hobley)
  * Improved screen-reader labels for action links in page listing (Helen Chapman, Katie Locke)
  * Added screen-reader labels for table headings in page listing (Helen Chapman, Katie Locke)
diff --git a/CODE_OF_CONDUCT.md b/CODE_OF_CONDUCT.md
index 9280552f6c..8bf933a45d 100644
--- a/CODE_OF_CONDUCT.md
+++ b/CODE_OF_CONDUCT.md
@@ -11,7 +11,7 @@ orientation.
 
 ## Our Standards
 
-Examples of behavior that contributes to creating a positive environment
+Examples of behaviour that contributes to creating a positive environment
 include:
 
 -   Using welcoming and inclusive language
@@ -20,7 +20,7 @@ include:
 -   Focusing on what is best for the community
 -   Showing empathy towards other community members
 
-Examples of unacceptable behavior by participants include:
+Examples of unacceptable behaviour by participants include:
 
 -   The use of sexualized language or imagery and unwelcome sexual attention or advances
 -   Trolling, insulting/derogatory comments, and personal or political attacks
@@ -31,13 +31,13 @@ Examples of unacceptable behavior by participants include:
 ## Our Responsibilities
 
 Project maintainers are responsible for clarifying the standards of acceptable
-behavior and are expected to take appropriate and fair corrective action in
-response to any instances of unacceptable behavior.
+behaviour and are expected to take appropriate and fair corrective action in
+response to any instances of unacceptable behaviour.
 
 Project maintainers have the right and responsibility to remove, edit, or
 reject comments, commits, code, wiki edits, issues, and other contributions
 that are not aligned to this Code of Conduct, or to ban temporarily or
-permanently any contributor for other behaviors that they deem inappropriate,
+permanently any contributor for other behaviours that they deem inappropriate,
 threatening, offensive, or harmful.
 
 ## Scope
@@ -51,7 +51,7 @@ further defined and clarified by project maintainers.
 
 ## Enforcement
 
-Instances of abusive, harassing, or otherwise unacceptable behavior may be
+Instances of abusive, harassing, or otherwise unacceptable behaviour may be
 reported by contacting the project team at <hello@wagtail.org>. All
 complaints will be reviewed and investigated and will result in a response that
 is deemed necessary and appropriate to the circumstances. The project team is
diff --git a/client/src/api/client.js b/client/src/api/client.js
index e6e34886c2..51f4647bc9 100644
--- a/client/src/api/client.js
+++ b/client/src/api/client.js
@@ -38,7 +38,7 @@ const timeout = (ms, promise) => {
 };
 
 /**
- * Wrapper around fetch with sane defaults for behavior in the face of
+ * Wrapper around fetch with sane defaults for behaviour in the face of
  * errors.
  */
 const request = (method, url) => {
diff --git a/docs/advanced_topics/accessibility_considerations.rst b/docs/advanced_topics/accessibility_considerations.rst
index 1b4b2b4d79..e1a14af8cf 100644
--- a/docs/advanced_topics/accessibility_considerations.rst
+++ b/docs/advanced_topics/accessibility_considerations.rst
@@ -24,7 +24,7 @@ As part of defining your site’s models, here are areas to pay special attentio
 Alt text for images
 -------------------
 
-The default behavior for Wagtail images is to use the ``title`` field as the alt text (`#4945 <https://github.com/wagtail/wagtail/issues/4945>`_).
+The default behaviour for Wagtail images is to use the ``title`` field as the alt text (`#4945 <https://github.com/wagtail/wagtail/issues/4945>`_).
 This is inappropriate, as it’s not communicated in the CMS interface, and the image upload form uses the image’s filename as the title by default.
 
 Ideally, always add an optional “alt text” field wherever an image is used, alongside the image field:
diff --git a/docs/contributing/ui_guidelines.md b/docs/contributing/ui_guidelines.md
index 941657e07f..08c081ec3b 100644
--- a/docs/contributing/ui_guidelines.md
+++ b/docs/contributing/ui_guidelines.md
@@ -22,7 +22,7 @@ We use [djhtml](https://github.com/rtts/djhtml) for formatting and [Curlylint](h
 
 - Write [valid](https://validator.w3.org/nu/), [semantic](https://html5doctor.com/element-index/) HTML.
 - Follow [ARIA authoring practices](https://w3c.github.io/aria-practices/), in particular [No ARIA is better than Bad ARIA](https://w3c.github.io/aria-practices/#no_aria_better_bad_aria).
-- Use classes for styling, `data-` attributes for JavaScript behavior, IDs for semantics only.
+- Use classes for styling, `data-` attributes for JavaScript behaviour, IDs for semantics only.
 - For comments, use [Django template syntax](https://docs.djangoproject.com/en/stable/ref/templates/language/#comments) instead of HTML.
 
 ## CSS guidelines
diff --git a/docs/releases/2.5.rst b/docs/releases/2.5.rst
index 306857f764..a32a0e0ca3 100644
--- a/docs/releases/2.5.rst
+++ b/docs/releases/2.5.rst
@@ -143,7 +143,7 @@ Wagtail now has built-in support for new rich text formats, disabled by default:
 * ``strikethrough``, using the ``STRIKETHROUGH`` Draft.js inline style, saved as a ``<s>`` tag.
 * ``code``, using the ``CODE`` Draft.js inline style, saved as a ``<code>`` tag.
 
-Projects already using those exact Draft.js type and HTML tag combinations can safely replace their feature definitions with the new built-ins. Projects that use the same feature identifier can keep their existing feature definitions as overrides. Finally, if the Draft.js types / HTML tags are used but with a different combination, do not enable the new feature definitions to avoid conflicts in storage or editor behavior.
+Projects already using those exact Draft.js type and HTML tag combinations can safely replace their feature definitions with the new built-ins. Projects that use the same feature identifier can keep their existing feature definitions as overrides. Finally, if the Draft.js types / HTML tags are used but with a different combination, do not enable the new feature definitions to avoid conflicts in storage or editor behaviour.
 
 
 ``register_link_type`` and ``register_embed_type`` methods for rich text tag rewriting have changed
diff --git a/docs/releases/2.6.rst b/docs/releases/2.6.rst
index f372edc8ce..fffe3f0092 100644
--- a/docs/releases/2.6.rst
+++ b/docs/releases/2.6.rst
@@ -71,7 +71,7 @@ Other features
 * Added support for custom search handler classes to modeladmin's IndexView, and added a class that uses the default Wagtail search backend for searching (Seb Brown, Andy Babic)
 * Update group edit view to expose the ``Permission`` object for each checkbox (George Hickman)
 * Improve performance of Pages for Moderation panel (Fidel Ramos)
-* Added ``process_child_object`` and ``exclude_fields`` arguments to ``Page.copy()`` to make it easier for third-party apps to customise copy behavior (Karl Hobley)
+* Added ``process_child_object`` and ``exclude_fields`` arguments to ``Page.copy()`` to make it easier for third-party apps to customise copy behaviour (Karl Hobley)
 * Added ``Page.with_content_json()``, allowing revision content loading behaviour to be customised on a per-model basis (Karl Hobley)
 * Added ``construct_settings_menu`` hook (Jordan Bauer, Quadric)
 * Fixed compatibility of date / time choosers with wagtail-react-streamfield (Mike Hearn)
diff --git a/docs/releases/2.8.rst b/docs/releases/2.8.rst
index 7eab431a22..d99c1cdd75 100644
--- a/docs/releases/2.8.rst
+++ b/docs/releases/2.8.rst
@@ -29,7 +29,7 @@ Other features
 
 * Removed leftover Python 2.x compatibility code (Sergey Fedoseev)
 * Combine flake8 configurations (Sergey Fedoseev)
-* Improve diffing behavior for text fields (Aliosha Padovani)
+* Improve diffing behaviour for text fields (Aliosha Padovani)
 * Improve contrast of disabled inputs (Nick Smith)
 * Added ``get_document_model_string`` function (Andrey Smirnov)
 * Added support for Cloudflare API tokens for frontend cache invalidation (Tom Usher)
diff --git a/docs/releases/3.0.md b/docs/releases/3.0.md
index 96af6fdf07..4cd31a0195 100644
--- a/docs/releases/3.0.md
+++ b/docs/releases/3.0.md
@@ -113,7 +113,7 @@ When using a queryset to render a list of items with images, you can now make us
  * Make sure the focus outline of checkboxes is fully around the outer border (Steven Steinwand)
  * Consistently set `aria-haspopup="menu"` for all sidebar menu items that have sub-menus (LB (Ben Johnston))
  * Make sure `aria-expanded` is always explicitly set as a string in sidebar (LB (Ben Johnston))
- * Use a button element instead of a link for page explorer menu item, for the correct semantics and behavior (LB (Ben Johnston))
+ * Use a button element instead of a link for page explorer menu item, for the correct semantics and behaviour (LB (Ben Johnston))
  * Make sure the “Title” column label can be translated in the page chooser and page move UI (Stephanie Cheng Smith)
  * Remove redundant `role="main"` attributes on `<main>` elements causing HTML validation issues (Luis Espinoza)
  * Allow bulk publishing of pages without revisions (Andy Chosak)
diff --git a/wagtail/contrib/routable_page/tests.py b/wagtail/contrib/routable_page/tests.py
index 3298daffe6..aa182616b8 100644
--- a/wagtail/contrib/routable_page/tests.py
+++ b/wagtail/contrib/routable_page/tests.py
@@ -170,7 +170,7 @@ class TestRoutablePage(TestCase):
     def test_routable_page_can_have_instance_bound_descriptors(self):
         # This descriptor pretends that it does not exist in the class, hence
         # it raises an AttributeError when class bound. This is, for instance,
-        # the behavior of django's FileFields.
+        # the behaviour of django's FileFields.
         class InstanceDescriptor:
             def __get__(self, instance, cls=None):
                 if instance is None:
diff --git a/wagtail/documents/migrations/0011_add_choose_permissions.py b/wagtail/documents/migrations/0011_add_choose_permissions.py
index 6c3b717616..a96589f8b9 100644
--- a/wagtail/documents/migrations/0011_add_choose_permissions.py
+++ b/wagtail/documents/migrations/0011_add_choose_permissions.py
@@ -21,7 +21,7 @@ def add_choose_permission_to_admin_groups(apps, _schema_editor):
     )
 
     # Assign it to all groups which have "Access the Wagtail admin" permission.
-    # This emulates the previous behavior, where everyone who would access the admin
+    # This emulates the previous behaviour, where everyone who would access the admin
     # could choose any document in any Collection, because choosing wasn't permissioned.
     for group in Group.objects.filter(permissions__codename="access_admin"):
         group.permissions.add(choose_document_permission)
diff --git a/wagtail/documents/tests/test_models.py b/wagtail/documents/tests/test_models.py
index ece0dbc147..793770fa2e 100644
--- a/wagtail/documents/tests/test_models.py
+++ b/wagtail/documents/tests/test_models.py
@@ -240,7 +240,7 @@ class TestFilesDeletedForCustomModels(TestFilesDeletedForDefaultModels):
         )
 
         #: Sadly signal receivers only get connected when starting django.
-        #: We will re-attach them here to mimic the django startup behavior
+        #: We will re-attach them here to mimic the django startup behaviour
         #: and get the signals connected to our custom model..
         signal_handlers.register_signal_handlers()
 
diff --git a/wagtail/images/migrations/0023_add_choose_permissions.py b/wagtail/images/migrations/0023_add_choose_permissions.py
index 5a88da598c..5648ac6b7a 100644
--- a/wagtail/images/migrations/0023_add_choose_permissions.py
+++ b/wagtail/images/migrations/0023_add_choose_permissions.py
@@ -21,7 +21,7 @@ def add_choose_permission_to_admin_groups(apps, _schema_editor):
     )
 
     # Assign it to all groups which have "Access the Wagtail admin" permission.
-    # This emulates the previous behavior, where everyone could choose any image in any Collection
+    # This emulates the previous behaviour, where everyone could choose any image in any Collection
     # because choosing wasn't permissioned.
     for group in Group.objects.filter(permissions__codename="access_admin"):
         group.permissions.add(choose_image_permission)
diff --git a/wagtail/images/tests/test_signal_handlers.py b/wagtail/images/tests/test_signal_handlers.py
index b6ae96e9a7..e551985315 100644
--- a/wagtail/images/tests/test_signal_handlers.py
+++ b/wagtail/images/tests/test_signal_handlers.py
@@ -71,7 +71,7 @@ class TestFilesDeletedForCustomModels(TestFilesDeletedForDefaultModels):
         )
 
         #: Sadly signal receivers only get connected when starting django.
-        #: We will re-attach them here to mimic the django startup behavior
+        #: We will re-attach them here to mimic the django startup behaviour
         #: and get the signals connected to our custom model..
         signal_handlers.register_signal_handlers()
 
diff --git a/wagtail/models/sites.py b/wagtail/models/sites.py
index 7bf5c80a26..92eac13f04 100644
--- a/wagtail/models/sites.py
+++ b/wagtail/models/sites.py
@@ -160,7 +160,7 @@ class Site(models.Model):
             site = get_site_for_hostname(hostname, port)
         except Site.DoesNotExist:
             pass
-            # copy old SiteMiddleware behavior
+            # copy old SiteMiddleware behaviour
         return site
 
     @property