Previews lose images if the image moves

[billkendrick]

Steps to reproduce the problem

After moving image files on my webserver to new URLs, Mastodon posts where I linked to pages that included those images are no longer showing them in the previews -- despite both updating og:image and creating HTTP redirects from the images' old URLs to their new ones.

Expected behaviour

Previews of images on my links should [continue] to appear

Actual behaviour

Previews of images on my links have all disappeared

Detailed description

Today on my webserver, I moved a large collection of image files from a single directory into subdirectories (e.g., "abc.png" went into "a/abc.png"; "xyz.jpg" went into "x/xyz.jpg").

My pages that show these images, e.g., https://tuxpaint.org/gallery/image.php?i=ethans-death-and-taxes-by-reddit-crankgameplays.png, have been update to not only use the correct path in the <img src> tag, but the <meta property="og:image" ...> has as well.

Furthermore, for situations where someone or something (cough previews on posts made to Meta Threads) still expected to find the image at the original location, I have set up a 404 error handler on my webserver that detects the old URLs for these images (e.g., "/gallery/images/whatever.png"), and uses a Location: HTTP header to redirect to the new URL (e.g., "/gallery/images/w/whatever.png").

Unfortunately, when I look at my older posts to my Mastodon account, all of the link previews now show a generic "document" icon in a big great box, rather than a thumbnail of the og:image image. 😞

Example: https://floss.social/@tuxpaint/112312826625820531

Compare to a more recent post (after I had moved the images into subdirectories): https://floss.social/@tuxpaint/112370349577998010

Mastodon instance

floss.social

Mastodon version

v4.2.8

Browser name and version

Chrome 124.0.6367.91

Operating system

Ubuntu 22.04.4

Technical details

No response