Upload.wikimedia.org

Uploaded image and media files for Wikimedia's wikis appear on the separate subdomain upload.wikimedia.org.

This provides separate physical hosting for efficiency, a separate domain name to aid in browser connection splitting, and a separate domain name to aid in JavaScript security rules.

Caching layer

Uploads have a separate set of squid proxy caches from the text squids; this avoids contention between the two data sets, which have different characteristics for object size, update rate, etc.

Backend: scaling

[3:33pm] mark: 01:31:52 <TimStarling> the first is for thumb.php requests by users, the second is for ordinary requests via the 404 handler
[3:34pm] mark: so it's accessed in two ways
[3:34pm] mark: one via squid directly

please add more documentation thx

Private wikis

Our private wikis do not serve their files to the public through this interface; they're served through img_auth.php on the local domain, which enforced authentication.

Compatibility links

Most of our wikis have an rewrite rule to redirect requests from /upload and /math on the primary wiki domain to the appropriate subdirectory on upload.wikimedia.org. This provides compatbility for old direct image links from the days before the separate image hosting.

Special:Filepath can also send redirects here.