# What is the status of the imgur images on MathOverflow?

Many posts on MO contain a link to imgur.com. Such links can be created outside the Stack Exchange network - if somebody simply creates a picture on imgur. But some of them might have been uploaded through the Stack Exchange interface. Currently such links will have the format i.stack.imgur.com rather than a link to i.imgur.com. But this was not always the case.

As far as I can tell, at some point there were two changes to the way images are uploaded in the Stack Exchange editor. Since August 2010, Stack Exchange can upload to an imgur account which is not subject to 6 months limit - making them more-or-less permanent.1 This also led to changing the format of the links from i.imgur.com to i.stack.imgur.com. Stack Exchange updated the links from the old format to the new one network-wide.2

All of this happened before MathOverflow joined the Stack Exchange network. So the update by the Stack Exchange team did not influence MathOverflow. Was such an update perhaps done by the MO mods at the time? Or was it done by SE after MO joined the network?

It seems that there are still at least some links to i.imgur.com which could be fixed by i.stack.imgur.com.

Questions.

• What are the reasons for the broken i.imgur.com links which are supposed to be in the format i.stack.imgur.com? Is it likely that there are many such links? Or are these examples only some rare exceptions?
• Is it possible to find all links of this type? (I.e., the links where simply changing the URL to i.stack.imgur.com would fix the picture.)
• Was a clean-up of imgur links done on MathOverflow at some point? (Similar as the clean-up done on other sites - which were part of the network in 2010.)
• Can such links be fixed only manually? Or is it possible to do this automatically.

I suppose that there are only a very few posts of this type. Search returns only 111 posts with such links. SEDE returns 111 posts and 114 if we search in MarkDown.)

All posts of this kind (i.e., where adding stack into the URL helps) that I was able to find are listed below. As you can see, it is a rather short list.

At the same time, it is a bit unclear how the changes back in 2010 influenced MO - which was at the time outside of the network and on the older version of the Stack Exchange software. So it seemed reasonable to ask about this - perhaps there are some people who are aware of the details.

Later I managed to find four instances on Mathematics Stack Exchange: 2508, 2525, 2549, 2569. All four were posted in August 2010 - on MO, the dates of the posts listed below vary much more than that.

Examples