diff --git a/404.rst b/404.rst
index 21960757c60..0cf80c065a4 100644
--- a/404.rst
+++ b/404.rst
@@ -22,3 +22,42 @@ Page not found
         <a href="#" onclick="$('#rtd-search-form [name=\\'q\\']').focus()">Search docs</a>
         box on the left or <a href="/">go to the homepage</a>.
     </p>
+
+    <script>
+    // If we were redirected to `/en/4.x/` as a result of the RTD language selector,
+    // redirect to `/en/stable/` instead, as English does not have a `4.x` branch.
+    // (For maintenance reasons, non-English languages have a single `4.x` branch
+    // that is the counterpart of `4.3`, `4.4`, `4.5`, and so on.)
+    if (window.location.pathname.includes('/en/4.x/')) {
+      const newUrl = window.location.pathname.replace('/en/4.x/', '/en/stable/');
+      window.location.replace(newUrl);
+    }
+
+    // Check for redirects if on a currently invalid page.
+    // This is done in JavaScript, as we exceed Read the Docs' limit for the amount of redirects configurable.
+    // When testing this feature on a local web server, replace the URL below with just `/_static/redirects.csv`.
+    fetch("/en/latest/_static/redirects.csv")
+      .then(response => response.text())
+      .then(csvText => {
+        const lines = csvText.trim().split('\n');
+        for (const line of lines) {
+          if (!line.trim()) {
+            continue;
+          }
+          const [from, to] = line.split(',').map(s => s.trim());
+          if (from && to) {
+            if (window.location.pathname.endsWith(from)) {
+              if (to.startsWith('https://')) {
+                window.location.replace(to);
+              } else {
+                const newUrl = window.location.href.replace(window.location.pathname, to);
+                window.location.replace(newUrl);
+              }
+            }
+          }
+        }
+      })
+      .catch(err => {
+        console.error("Couldn't fetch redirects list:", err);
+      });
+    </script>
diff --git a/_static/js/custom.js b/_static/js/custom.js
index d028dd0f329..49cd5fc2618 100644
--- a/_static/js/custom.js
+++ b/_static/js/custom.js
@@ -1,4 +1,3 @@
-
 // Handle page scroll and adjust sidebar accordingly.
 
 // Each page has two scrolls: the main scroll, which is moving the content of the page;
diff --git a/_tools/redirects/redirects.csv b/_static/redirects.csv
similarity index 97%
rename from _tools/redirects/redirects.csv
rename to _static/redirects.csv
index 14f19a965c9..664ab8ce08b 100644
--- a/_tools/redirects/redirects.csv
+++ b/_static/redirects.csv
@@ -431,20 +431,20 @@ source,destination
 /contributing/workflow/testing_pull_requests.html,https://contributing.godotengine.org/en/latest/organization/pull_requests/testing.html
 /contributing/development/core_and_modules/2d_coordinate_systems.html,/engine_details/architecture/2d_coordinate_systems.html
 /contributing/development/core_and_modules/common_engine_methods_and_macros.html,/engine_details/architecture/common_engine_methods_and_macros.html
-/contributing/development/core_and_modules/core_types.html,//architecture/core_types.html
-/contributing/development/core_and_modules/custom_audiostreams.html,//architecture/custom_audiostreams.html
-/contributing/development/core_and_modules/custom_godot_servers.html,//architecture/custom_godot_servers.html
-/contributing/development/core_and_modules/custom_modules_in_cpp.html,//architecture/custom_modules_in_cpp.html
-/contributing/development/core_and_modules/custom_platform_ports.html,//architecture/custom_platform_ports.html
-/contributing/development/core_and_modules/custom_resource_format_loaders.html,//architecture/custom_resource_format_loaders.html
-/contributing/development/core_and_modules/godot_architecture_diagram.html,//architecture/godot_architecture_diagram.html
-/contributing/development/core_and_modules/index.html,//architecture/index.html
-/contributing/development/core_and_modules/inheritance_class_tree.html,//architecture/inheritance_class_tree.html
-/contributing/development/core_and_modules/internal_rendering_architecture.html,//architecture/internal_rendering_architecture.html
-/contributing/development/core_and_modules/object_class.html,//architecture/object_class.html
-/contributing/development/core_and_modules/scripting_development.html,//architecture/scripting_development.html
-/contributing/development/core_and_modules/unit_testing.html,//architecture/unit_testing.html
-/contributing/development/core_and_modules/variant_class.html,//architecture/variant_class.html
+/contributing/development/core_and_modules/core_types.html,/engine_details/architecture/core_types.html
+/contributing/development/core_and_modules/custom_audiostreams.html,/engine_details/architecture/custom_audiostreams.html
+/contributing/development/core_and_modules/custom_godot_servers.html,/engine_details/architecture/custom_godot_servers.html
+/contributing/development/core_and_modules/custom_modules_in_cpp.html,/engine_details/architecture/custom_modules_in_cpp.html
+/contributing/development/core_and_modules/custom_platform_ports.html,/engine_details/architecture/custom_platform_ports.html
+/contributing/development/core_and_modules/custom_resource_format_loaders.html,/engine_details/architecture/custom_resource_format_loaders.html
+/contributing/development/core_and_modules/godot_architecture_diagram.html,/engine_details/architecture/godot_architecture_diagram.html
+/contributing/development/core_and_modules/index.html,/engine_details/architecture/index.html
+/contributing/development/core_and_modules/inheritance_class_tree.html,/engine_details/architecture/inheritance_class_tree.html
+/contributing/development/core_and_modules/internal_rendering_architecture.html,/engine_details/architecture/internal_rendering_architecture.html
+/contributing/development/core_and_modules/object_class.html,/engine_details/architecture/object_class.html
+/contributing/development/core_and_modules/scripting_development.html,/engine_details/architecture/scripting_development.html
+/contributing/development/core_and_modules/unit_testing.html,/engine_details/architecture/unit_testing.html
+/contributing/development/core_and_modules/variant_class.html,/engine_details/architecture/variant_class.html
 /contributing/documentation/class_reference_primer.html,engine_details/class_reference/index.html
 /contributing/development/compiling/compiling_for_android.html,/engine_details/development/compiling/compiling_for_android.html,
 /contributing/development/compiling/compiling_for_ios.html,/engine_details/development/compiling/compiling_for_ios.html
diff --git a/_tools/redirects/README.md b/_tools/redirects/README.md
index af31b2f2a3f..c991b956426 100644
--- a/_tools/redirects/README.md
+++ b/_tools/redirects/README.md
@@ -21,19 +21,26 @@ To interact with the Read the Docs API, a valid API key must be set as
 
 ## Usage
 
-Let's say we recently renamed some files in the Git branch `3.4` (compared to the `stable` branch), and now we want to create redirects for these.
-For this, we would (after setting up the API token and requirements, see Setup above):
+Let's say we recently renamed some files in the Git branch `3.4` (compared to the `stable` branch),
+and now we want to create redirects for these. For this, we would (after setting up the API token
+and requirements, see Setup above):
 
-> python convert_git_renames_to_csv.py stable 3.4
+```
+python convert_git_renames_to_csv.py stable 3.4
+```
 
 This should output a list of the redirects to create. Let's append these to the redirects file:
 
-> python convert_git_renames_to_csv.py stable 3.4 >> redirects.csv
+```
+python convert_git_renames_to_csv.py stable 3.4 >> ../../_tools/redirects.csv
+```
 
-After this, redirects for renamed files should have been appended to `redirects.csv`. You may want to double-check that!
-Now let's submit these to ReadTheDocs and create redirects there:
+After this, redirects for renamed files should have been appended to `../../_tools/redirects.csv`.
+You may want to double-check that! Now let's submit these to ReadTheDocs and create redirects there:
 
-> python create_redirects.py
+```
+python create_redirects.py
+```
 
 And that should be it!
 
diff --git a/_tools/redirects/create_redirects.py b/_tools/redirects/create_redirects.py
index baef253c4e6..67c5fd9563b 100644
--- a/_tools/redirects/create_redirects.py
+++ b/_tools/redirects/create_redirects.py
@@ -50,7 +50,7 @@ def parse_command_line_args():
         "-f",
         "--file",
         metavar="file",
-        default="redirects.csv",
+        default="../../_static/redirects.csv",
         type=str,
         help="Path to a CSV file used to keep a list of redirects, containing two columns: source and destination.",
     )