diff --git a/shelfmark/release_sources/__init__.py b/shelfmark/release_sources/__init__.py
index 1f3a9923..0091c297 100644
--- a/shelfmark/release_sources/__init__.py
+++ b/shelfmark/release_sources/__init__.py
@@ -15,6 +15,7 @@ if TYPE_CHECKING:
     from shelfmark.core.search_plan import ReleaseSearchPlan
     from shelfmark.download.postprocess.packs import PackFile
 
+from shelfmark.core.logger import redact_secrets
 from shelfmark.metadata_providers import BookMetadata
 
 
@@ -29,7 +30,16 @@ class ReleaseProtocol(StrEnum):
 
 
 class SourceUnavailableError(Exception):
-    """Raised when a source is configured but currently unreachable."""
+    """Raised when a source is configured but currently unreachable.
+
+    The message is shown to whoever ran the search, and it is usually built from a requests
+    exception whose text carries the request URL. A source that puts its key in the query
+    string (Jackett's ``apikey=``) would hand that key to every user, so credentials are
+    masked here for every source rather than at each place that raises.
+    """
+
+    def __init__(self, message: object = "") -> None:
+        super().__init__(redact_secrets(str(message)))
 
 
 @dataclass
diff --git a/tests/core/test_source_unavailable_error.py b/tests/core/test_source_unavailable_error.py
new file mode 100644
index 00000000..074fe20c
--- /dev/null
+++ b/tests/core/test_source_unavailable_error.py
@@ -0,0 +1,22 @@
+from shelfmark.release_sources import SourceUnavailableError
+
+
+def test_a_credential_query_parameter_is_masked_in_the_message():
+    error = SourceUnavailableError(
+        "could not reach it: http://host/api?t=book&apikey=SECRETKEY123&q=x"
+    )
+
+    assert "SECRETKEY123" not in str(error)
+    assert "apikey=(removed)" in str(error)
+
+
+def test_userinfo_is_masked_in_the_message():
+    error = SourceUnavailableError("could not reach http://user:hunter2@host:9117/api")
+
+    assert "hunter2" not in str(error)
+
+
+def test_a_plain_message_is_unchanged():
+    message = "every indexer is disabled by Prowlarr after recent failures (until 12:00)"
+
+    assert str(SourceUnavailableError(message)) == message
diff --git a/tests/jackett/test_jackett.py b/tests/jackett/test_jackett.py
index 86d6ad9f..322a9278 100644
--- a/tests/jackett/test_jackett.py
+++ b/tests/jackett/test_jackett.py
@@ -212,6 +212,40 @@ class TestSource:
         ):
             JackettSource().search(_book(), _plan())
 
+    def test_an_unreachable_jackett_does_not_put_its_api_key_in_the_error(self, jackett_config):
+        # requests puts the request URL, apikey included, in a connection error's text.
+        client = JackettClient("http://jackett:9117", "SECRETKEY123")
+        error = requests.exceptions.ConnectionError(
+            "HTTPConnectionPool(host='jackett', port=9117): Max retries exceeded with url: "
+            "/api/v2.0/indexers/all/results/torznab/api?apikey=SECRETKEY123&t=book&q=dune"
+        )
+        with (
+            patch.object(JackettSource, "_get_client", return_value=client),
+            patch.object(client._session, "get", side_effect=error),
+            pytest.raises(SourceUnavailableError) as raised,
+        ):
+            JackettSource().search(_book(), _plan())
+
+        assert "SECRETKEY123" not in str(raised.value)
+        assert "Max retries exceeded" in str(raised.value)
+
+    def test_the_indexer_lookup_error_does_not_put_the_api_key_in_the_message(self, jackett_config):
+        client = JackettClient("http://jackett:9117", "SECRETKEY123")
+        error = requests.exceptions.ConnectionError(
+            "HTTPConnectionPool(host='jackett', port=9117): Max retries exceeded with url: "
+            "/api/v2.0/indexers/all/results/torznab/api?t=indexers&configured=true"
+            "&apikey=SECRETKEY123"
+        )
+        with (
+            patch.object(JackettSource, "_get_client", return_value=client),
+            patch.object(client._session, "get", side_effect=error),
+            pytest.raises(SourceUnavailableError) as raised,
+        ):
+            JackettSource().search(_book(), _plan(indexers=["Alpha"]))
+
+        assert "SECRETKEY123" not in str(raised.value)
+        assert str(raised.value).startswith("could not reach Jackett")
+
     def test_auto_expand_retries_without_categories(self, jackett_config):
         jackett_config["JACKETT_AUTO_EXPAND"] = True
         client = MagicMock()