If you’ve ever clicked on a screenshot in the WordPress plugin directory and received a download prompt, you’re not the only one. In fact, it’s a widespread issue that affects a number of plugins. Screenshots are important as they help with troubleshooting, previewing features, and give users a sense of what to expect when it’s activated. But if you can’t see important details, they’re a moot point.
Mika Epstein, who reviews plugins before they’re added to the directory, wrote about the issue in early 2014. The prompt appears for images that use the incorrect MIME Type. Otto explains how to set the correct MIME Type using TortiseSVN on Windows or where to look if you use a different SVN client.
On Windows, using TortoiseSVN, you can right click the screenshot file, and select the TortoiseSVN->Properties menu. There you will find the svn:mime-type property, probably incorrectly set to “application/octet-stream”. Change that to the proper mime type of “image/png” or “image/jpg” accordingly. Afterwards, commit the change.
If you prefer command line SVN:
svn propset svn:mime-type image/png screenshot-1.png
Or similar. If somebody uses a different SVN client, look for “properties” and then the svn:mime-type property.
Once the changes are made, upload them to the plugin directory. They’ll take effect once the directory is synchronized. It’s a simple change that vastly improves the effectiveness and user experience of viewing screenshots.