diff --git a/socials_util/__init__.py b/socials_util/__init__.py
index 5a45d9b..d102ec4 100644
--- a/socials_util/__init__.py
+++ b/socials_util/__init__.py
@@ -316,6 +316,7 @@ WELL_KNOWN_MASTODON_INSTANCES = frozenset({
     'mastodon.uno',
     'mastodonapp.uk',
     'fosstodon.org',
+    'idlethumbs.social',
 })
 
 def determine_social_from_url_internally(url: str):