[html] when I try to open an HTML file through `http://localhost/xampp/htdocs/index.html` it says unable to connect to localhost

Start your XAMPP server by using:

  • {XAMPP}\xampp-control.exe
  • {XAMPP}\apache_start.bat

Then you have to use the URI http://localhost/index.html because htdocs is the document root of the Apache server.

If you're getting redirected to http://localhost/xampp/*, then index.php located in the htdocs folder is the problem because index.php files have a higher priority than index.html files. You could temporarily rename index.php.