Miraheze/en

Miraheze is a free, non-profit wiki hosting service that uses MediaWiki as its hosting engine, it provides any extension of your choice, including VisualEditor and Flow. Miraheze is not advertising supported, and does not include any advertising on wikis it hosts.

Extensions
Miraheze can download any extension of your wish and enable it on your wiki after it passes a security review. Many of these can be found at Wikimedia's Git code repositories. To see extensions that are currently downloaded on Miraheze see their github.

There are also Extensions by Miraheze, available as free open source software.

Custom domains
If requested, Miraheze provides support for custom domains, but under some conditions.

Code
Miraheze uses open-source code, and hosts it at GitHub.

Issue reporting
Miraheze uses their own Phabricator for issue/bug reports as well as requesting features for wikis.

Servers
Miraheze currently functions with 15 different servers used for different purposes (MediaWiki, Varnish, Database, Puppet, etc.). A list of these servers and each of their functions can be seen here.