An HTTP checker is a fundamental diagnostic tool that examines the Hypertext Transfer Protocol response of a given URL. At its most basic, it verifies if a website or specific page is live and responding to requests. However, advanced http checker provide a wealth of information beyond simple uptime, including the complete HTTP header response. This reveals the server type, content type, date, connection status, and crucially, the HTTP status code (like 200 OK, 301 Moved Permanently, 404 Not Found, or 500 Server Error). It can also check for specific header directives like X-Robots-Tag, cache-control settings, and security headers.