ProcessWire CORS

Basic Fix

PHP

header("Access-Control-Allow-Origin: http://your-origin-site.com");
header("Access-Control-Allow-Methods: GET, POST, OPTIONS");
header("Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept");

Apache

Header set Access-Control-Allow-Origin "http://your-origin-site.com"
Header set Access-Control-Allow-Methods "GET, POST, OPTIONS"
Header set Access-Control-Allow-Headers "Origin, X-Requested-With, Content-Type, Accept"

Fix with HTMX

PHP

header("Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept, hx-current-url, hx-request");

Apache

Header set Access-Control-Allow-Headers "Origin, X-Requested-With, Content-Type, Accept, hx-current-url, hx-request"

There might be more CORS settings necessary for HTMX!!!