DeepL offers a free API now

wagtail_localize/machine_translators/deepl.py

@@ -12,15 +12,25 @@ def language_code(code, is_target=False):
 
     return code.split("-")[0].upper()
 
+def auth_key_is_free_account(auth_key: str) -> bool:
+    # https://github.com/DeepLcom/deepl-python/blob/main/deepl/util.py
+    """Returns True if the given authentication key belongs to a DeepL API Free
+    account, otherwise False."""
+    return auth_key.endswith(":fx")
+
 
 class DeepLTranslator(BaseMachineTranslator):
     display_name = "DeepL"
-
+    _DEEPL_SERVER_URL = "https://api.deepl.com/v2/translate"
+    _DEEPL_SERVER_URL_FREE = "https://api-free.deepl.com/v2/translate"
+
     def translate(self, source_locale, target_locale, strings):
+        auth_key = self.options["AUTH_KEY"]
+        server_url = self._DEEPL_SERVER_URL_FREE if auth_key_is_free_account(auth_key) else self._DEEPL_SERVER_URL
         response = requests.post(
-            "https://api.deepl.com/v2/translate",
+            server_url,
             {
-                "auth_key": self.options["AUTH_KEY"],
+                "auth_key": auth_key,
                 "text": [string.data for string in strings],
                 "tag_handling": "xml",
                 "source_lang": language_code(source_locale.language_code),

wagtail_localize/machine_translators/tests/test_deepl_translator.py

@@ -0,0 +1,16 @@
+
+from django.test import TestCase
+
+from wagtail_localize.machine_translators.deepl import auth_key_is_free_account
+
+
+class TestDeeplTranslator(TestCase):
+    def setUp(self):
+        self.free_auth_key = "asd-23-ssd-243-adsf-dummy-auth-key:fx"
+        self.paid_auth_key = "asd-23-ssd-243-adsf-dummy-auth-key:bla"
+
+    def test_api_free(self):
+        self.assertEqual(auth_key_is_free_account(self.free_auth_key), True)
+
+    def test_api_paid(self):
+        self.assertEqual(auth_key_is_free_account(self.paid_auth_key), False)