Attempting to use the Similar Images Search feature at https://e621.net/iqdb_queries will fail if you use a link.

When pasting a link in the URL field and pressing 'Search'...
The page reloads and without changing the URL presents:
"
Access Denied: Not allowed to request content from this URL
You do not have permission to visit this page.
"

Links that cause this behavior (Seemingly all, but these are ones I've tried):
https://yt3.ggpht.com/Z7QeYWQKuF7VQ2-gsdZDbx3keCP4x_dWkxmZDmhEffztV3ZoBBM2wzlGpl_9QrH-RJRErBXS-g=w2120
https://yt3.ggpht.com/a/AATXAJyuaH5EmLuTnq8PqoxIPrj5iWk1j5xRmlHs5vQb=s900-c-k-c0xffffffff-no-rj-mo
https://yt3.ggpht.com/a/AATXAJyuaH5EmLuTnq8PqoxIPrj5iWk1j5xRmlHs5vQb=s0
https://www.google.com/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png
http://static1.e621proxy.ru/data/mascot_bg/raptor1.jpg
http://static1.e621proxy.ru/data/50/ba/50bac7d7e9749656c98485eed00a6e79.jpg

I cannot find a link that results in good behavior.
The File upload half of the search works as expected.

rust_out_mail_abuse said:
Attempting to use the Similar Images Search feature at https://e621.net/iqdb_queries will fail if you use a link.

When pasting a link in the URL field and pressing 'Search'...
The page reloads and without changing the URL presents:
"
Access Denied: Not allowed to request content from this URL
You do not have permission to visit this page.
"

Links that cause this behavior (Seemingly all, but these are ones I've tried):
https://yt3.ggpht.com/Z7QeYWQKuF7VQ2-gsdZDbx3keCP4x_dWkxmZDmhEffztV3ZoBBM2wzlGpl_9QrH-RJRErBXS-g=w2120
https://yt3.ggpht.com/a/AATXAJyuaH5EmLuTnq8PqoxIPrj5iWk1j5xRmlHs5vQb=s900-c-k-c0xffffffff-no-rj-mo
https://yt3.ggpht.com/a/AATXAJyuaH5EmLuTnq8PqoxIPrj5iWk1j5xRmlHs5vQb=s0
https://www.google.com/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png
http://static1.e621proxy.ru/data/mascot_bg/raptor1.jpg
http://static1.e621proxy.ru/data/50/ba/50bac7d7e9749656c98485eed00a6e79.jpg

I cannot find a link that results in good behavior.
The File upload half of the search works as expected.

The allowed URLs follow the same rules as the direct upload url whitelisting. e621 isn't a direct upload whitelisted domain, so it fails there.

kiranoot said:
The allowed URLs follow the same rules as the direct upload url whitelisting. e621 isn't a direct upload whitelisted domain, so it fails there.

That much is good to know. I feel like it should say that then as the error. Being told that the domain of the URL isn't allowed would be sufficient information.
The error that it currently spits out just leads me to think that the tool is broken. I hope that someone will change that.