Thread:Sannse/@comment-26933649-20171128171716/@comment-27345308-20171128175103

Because Wikia is checking the file extension, not the file type. The error message Davidjimnez (and any other user uploading a file whose file extension is wrong) got is confusing. Vignette, Wikia's service for generating thumbnails, is converting the image to a PNG afterwards anyways.