Drupal added support for IIS in 2010 and we have supported that and WAMP (Running Apache and PHP on Windows). Unfortunately, we have never been able to provide automated testing for these environments. And since 2010, the use of Microsoft products for hosting websites has declined. Because of this, the Drupal core committers propose drop support for Windows when used on production web sites in Drupal 11. Support for development on Windows will continue.
Source: RFC Remove support for Windows in production in Drupal 11
I didn’t know that IIS on Windows was still being used in production. I guess I need to get out more.

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