diff --git a/maintenance/clean_locales.py b/maintenance/clean_locales.py
new file mode 100644
index 0000000..9f55241
--- /dev/null
+++ b/maintenance/clean_locales.py
@@ -0,0 +1,79 @@
+import json
+from collections import OrderedDict
+from pathlib import Path
+from typing import Any
+
+# FIXME use Path
+ROOT_FOLDER = Path(__file__).parent.parent
+LOCALES_FOLDER = ROOT_FOLDER / "locales"
+LOCALES_LIST_FILE = ROOT_FOLDER / "maintenance" / "locales.json"
+LOCALE_FILES = {path.stem: path for path in LOCALES_FOLDER.glob("*.json")}
+ALL_LOCALES = set(LOCALE_FILES.keys())
+
+
+def get_json(path: Path) -> Any:
+    return json.loads(path.read_text(), object_pairs_hook=OrderedDict)
+
+
+def save_json(path: Path, data: Any, sort: bool = False) -> None:
+    with path.open("w", encoding="utf-8") as fp:
+        json.dump(data, fp, ensure_ascii=False, sort_keys=sort, indent=4)
+        fp.write("\n")
+
+
+def get_flatten_keys(d, parent_key=""):
+    items = set()
+
+    for k, v in d.items():
+        key = f"{parent_key}.{k}" if parent_key else k
+        items.add(key)
+
+        if isinstance(v, dict):
+            items |= get_flatten_keys(v, key)
+
+    return items
+
+
+def filter_data(data, stale_keys):
+    filtered = OrderedDict()
+
+    for k, v in data.items():
+        if k not in stale_keys:
+            value = v
+
+            if isinstance(v, OrderedDict):
+                nested_stale_keys = [
+                    key.replace(f"{k}.", "")
+                    for key in stale_keys
+                    if key.startswith(f"{k}.")
+                ]
+                if nested_stale_keys:
+                    value = filter_data(v, nested_stale_keys)
+
+            filtered[k] = value
+
+    return filtered
+
+
+def remove_stale_translations(ref="en", locales=None):
+    locales = set(locales) if locales else set(ALL_LOCALES)
+    locales.discard(ref)
+
+    ref_path = LOCALE_FILES[ref]
+    ref_data = get_json(ref_path)
+    ref_keys = get_flatten_keys(ref_data)
+
+    for locale in locales:
+        path = LOCALE_FILES[locale]
+        data = get_json(path)
+        keys = get_flatten_keys(data)
+        stale_keys = sorted(keys - ref_keys)
+        filtered_data = filter_data(data, stale_keys)
+        save_json(path, filtered_data)
+
+    # Resave ref file to sort and indent
+    save_json(ref_path, ref_data, sort=True)
+
+
+if __name__ == "__main__":
+    remove_stale_translations()