Originally this was a webp, but it's not supported by danbooru's uploader. Fortunately, you can select "view image"/open the image in a new tab, and change the "webp" in https://art.ngfiles.com/images/5113000/5113691_75182_aonoexorcist100_raaaa-animation-edit.0f74ed7925c31edaa21bec14eb4f173f.webp?f1696866845 to "gif", and it'll present the gif version. I wonder if that counts as webp-to-gif_conversion, or if it doesn't count because the website already had two versions?