w.wiki

w.wiki is the official Wikimedia URL shortener, powered by Extension:UrlShortener. It was designed and approved in an RfC. URL shorteners are evil and problematic in general because they obfuscate the link target and if/when the shortener disappears, you have no way of accessing the destination. But people will use them anyways, so we created one that was less evil.

Approved domains

URL shorteners are banned on most Wikimedia projects because they obfuscate the link target, making anti-spam work much harder. w.wiki is explicitly allowed because it has a list of approved domains, all of which go to Wikimedia sites.

To add a new domain to the list, it must meet the following criteria:

No open redirects (allows bypassing the allowed domains list)
No dangerous actions on GET requests
No reflective XSS
Should fall under the Wikimedia privacy policy or anyone who has access to private information (any PII such as IPs, User-agents, emails, etc.) should have signed an NDA.
Running software that goes through the code review process or comes from a trusted upstream (e.g. Debian)

Perennial requests that have been declined include *.toolforge.org and *.wmflabs.org (T231518), translatewiki.net (T238413) and qrwp.org (T249416).

Dumps

Weekly dumps are available with a mapping of short codes to targets: https://dumps.wikimedia.org/other/shorturls/

These are regularly uploaded to the Internet Archive.