Textpattern 4.4.1 requires a web server with:

In addition to the above minimum requirements, we recommend the following:

  • PHP 5.2+, in mod_php or fastcgi mode
  • MySQL 5
  • PHP extensions:
  • Apache 1.3+ or 2.0+ with mod_rewrite
  • A Unix server OS with locale support

Textpattern probably works on any web server that supports PHP. It is reported to work well on IIS and Lighttpd. Clean URLs are possible on those systems, with the right configuration, but are not officially supported. Read more about suitable Textpattern hosting here.