Large summary image unable to load image from IIIF image server


We have set up twitter cards on a new project and, although the cards validate and the images are publicly accessible the image will not display in the tweet or validator.

I have ensured that there is no robots.txt preventing crawling, and checked that images can be retrieved with curl -A Twitterbot

Images are within the size limits for this card type, summary_large_image.

Could this be a whitelisting issue? The images are served from a dedicated image server on a separate subdomain. I cannot find any tool to whitelist a domain separate from where the cards are hosted.

The project itself is not yet live but i have set up a sample that demonstrates the issue here



There’s no need for whitelisting for any cards other than player cards.

I think there is an issue with the SSL configuration of the image host - I see a handshake error when trying to retrieve the image.


Thank you for getting back to us. I did a check and spotted that there was a self signed certifcate within the certificate chain. We have removed this and it is no longer reporting as an error. The images are still unable to load in Twitter though. Could you let us know if you are still seeing the same issue, or a different one?


There’s still an issue:

$ echo -e "HEAD / HTTP/1.0\r\nHost:\r\n\r\n" | openssl s_client -servername -connect -state -quiet


SSL_connect:before/connect initialization
SSL_connect:SSLv2/v3 write client hello A
SSL3 alert read:warning:unrecognized name

This is an indication that the Apache config doesn’t have a matching serverName or serverAlias, usually. More in this thread.


Correcting the serverName config has fixed this. Thank you for your help.