og:image could not be downloaded because it exceeded the maximum allowed sized of 8Mb
This is a bug, and it's confirmed, after getting the warning, if you retry the debug, or click on "Scrape Again", the error message will be gone. This is an issue because if someone tries to share the post, the image will not show up since it didn't get scrapped, but subsequent shares will display the image.
You may subscribe to the Bug report or add some extra comments.
https://developers.facebook.com/bugs/1626463061012181/
And yeah, this started happening around April 17th, I hope this solves our issue.
EDIT:
Facebook Team replied with a workaround:
It seems like the issue is with the misleading error message which we will be updating. In the meantime, since the crawler has to see an image at least once before it can be rendered, it means that the first person who shares a piece of content won't see a rendered image. This seems to be the actual issue here and the workaround is available here: https://developers.facebook.com/docs/sharing/best-practices#precaching I will post here once we update the error message.
Adding the og:image:width and og:image:height Open Graph tags seems to do the trick, I can swear I tried that before and didn't do much, but this time it seems to work just fine.
This continues to be an issue in May 2017. I tried:
- adding og:image:width and og:image:height
- manually resizing the img to 1200x630 (FB's recommended minimum)
- rounding the size to the nearest hundredth (a sol'n I saw elsewhere)
- confirming that the filesize was indeed well below the 8MB (it's 322 KB)
- renamed the file to exclude non-alpha characters
- converting img to jpg.
The only "solution" in my case was to run the FB Sharing Debugger on the non-https:// version of the webpage (i.e. simply http://). Then the "og:image could not be downloaded because it exceeded the maximum allowed sized of 8Mb" error msg disappeared. FWIW, FB did show the 301 redirects from the http: to the https:.
(I would have posted this as a comment but do not have enough cred yet.)