What is HTTP Status Code?

An HTTP status code is a three-digit number returned by a web server in response to a client's request. These codes are part of the HTTP protocol standard and communicate whether a specific request was successful, redirected, or encountered an error. They are grouped into five classes based on the first digit.

The five classes are: 1xx (Informational) — the request is being processed; 2xx (Successful) — the request was received and understood; 3xx (Redirection) — further action is needed to complete the request; 4xx (Client Error) — the request contains bad syntax or cannot be fulfilled; and 5xx (Server Error) — the server failed to fulfill a valid request.

Common status codes include 200 OK, 301 Moved Permanently, 404 Not Found, and 500 Internal Server Error. Monitoring these codes is essential for understanding how users and search engines experience your website.

HTTP status codes directly impact both user experience and SEO. A high number of 4xx and 5xx errors indicates broken functionality, which frustrates users and drives them away. Search engines like Google treat persistent errors as a signal of poor site quality, which can lower your rankings.

For monitoring purposes, status codes tell you exactly what's happening with your site. A spike in 500 errors indicates a server issue that needs immediate attention. A growing number of 404s suggests broken internal links or deleted pages that should be redirected. Understanding these codes helps you diagnose problems quickly and prioritize fixes.

Status codes are also critical for monitoring configuration. When setting up uptime checks, you define which status codes count as "up" — typically 2xx codes, but sometimes 3xx redirects are acceptable for certain use cases. Misconfigured thresholds can lead to false positives or missed outages.

WebCheckly monitors HTTP status codes in real-time across all your monitoring checks. Each uptime check records the exact status code returned, along with response time and response body size. You can view historical status code distributions on your monitoring dashboard to identify trends, such as increasing 5xx errors during peak traffic.

WebCheckly's broken link checker crawls your site and reports the status code for every link it finds, making it easy to spot 404s, 500s, and other errors across your entire website. Combined with alert notifications, you'll know the moment a critical page starts returning error codes.

• Website Availability — How uptime monitoring uses status codes to determine site health.
• What is a Broken Link? — Broken links typically return 404 or 410 status codes.
• What is Technical SEO? — Status codes play a key role in crawlability and indexability.