Every time someone visits your website, the server responds with a three-digit number called an HTTP status code. Most visitors never see these codes directly, but they shape the entire browsing experience. Understanding them is essential for anyone who runs a website.
What Are HTTP Status Codes?
HTTP status codes are standardized responses from a web server indicating the result of a client's request. They fall into five categories:
- 1xx — Informational responses
- 2xx — Success
- 3xx — Redirection
- 4xx — Client errors
- 5xx — Server errors
For website owners, the codes that matter most are in the 2xx, 3xx, 4xx, and 5xx ranges. Let's break down the ones you will encounter regularly.
The Success Code: 200 OK
A 200 OK response means everything worked as expected. The server received the request, processed it, and returned the requested content. This is what you want every visitor to receive when they load your pages.
When an uptime monitoring tool checks your site, it looks for a 200 response as the primary indicator that your site is healthy. If your homepage suddenly stops returning 200, something is wrong, even if the server is technically still running.
Redirections: 301 and 302
A 301 Moved Permanently tells browsers and search engines that a page has permanently moved to a new URL. This is the correct code to use when you restructure your site or change a page's slug. Search engines will transfer the old page's ranking authority to the new URL.
A 302 Found (temporary redirect) signals that the move is temporary. Use this sparingly, as search engines will keep indexing the original URL.
Misconfigured redirects are a common source of problems. Redirect chains (one redirect pointing to another, then another) slow down page loads and can confuse crawlers.
Client Errors: 403 and 404
A 403 Forbidden response means the server understood the request but refuses to fulfill it. This usually happens when a visitor tries to access a restricted directory or a page that requires authentication. If legitimate visitors are hitting 403 errors, check your file permissions and access rules.
The 404 Not Found error is the most recognized status code on the internet. It means the requested page does not exist. Every site has some 404s, they are inevitable when pages get deleted or URLs get mistyped. But a spike in 404 errors can signal broken internal links, a botched migration, or external sites linking to pages you have removed.
Monitoring your 404 rate helps you catch these issues before they erode your search rankings and frustrate visitors.
Server Errors: 500, 502, and 503
Server errors are the ones that should trigger immediate attention.
500 Internal Server Error is a generic catch-all indicating something went wrong on the server side. It could be a bug in your application code, a database connection failure, or a misconfigured server. The vagueness of a 500 error is what makes it tricky. You need to check your server logs to find the root cause.
502 Bad Gateway occurs when a server acting as a gateway or proxy receives an invalid response from an upstream server. This is common in architectures where a reverse proxy like Nginx sits in front of an application server. If the application crashes or becomes unresponsive, Nginx returns a 502.
503 Service Unavailable means the server is temporarily unable to handle requests, typically due to being overloaded or undergoing maintenance. Unlike a 500, a 503 suggests the problem is temporary. Some teams intentionally return 503 during deployments so search engines know to come back later rather than de-indexing the page.
Why These Codes Matter for Site Health
Status codes are more than technical trivia. They directly affect three things:
- User experience — Visitors who hit errors leave. Studies show that even a single error page significantly increases bounce rates.
- SEO rankings — Search engine crawlers pay close attention to status codes. Persistent 5xx errors can cause pages to drop from search results entirely. Excessive 404s waste your crawl budget.
- Revenue — For e-commerce sites, every minute of 500 errors translates directly to lost sales.
How Monitoring Tools Use Status Codes
Uptime monitoring services like Sitewake regularly send requests to your website and check the HTTP status code in the response. If the response is anything other than a 2xx, the monitor flags it as a potential issue.
This is why simple "ping" monitoring is not enough. A server might respond to a ping but still return 500 errors to actual visitors. HTTP monitoring catches problems that network-level checks miss.
With Sitewake, you can monitor multiple endpoints across your site and get alerted the moment a status code changes from healthy to unhealthy. The free plan covers up to 3 monitors, which is enough to watch your homepage, API, and a critical landing page.
Quick Reference Table
| Code | Meaning | Action Required | | ---- | --------------------- | --------------------------------------- | | 200 | OK | None, everything is working | | 301 | Permanently moved | Verify the redirect target is correct | | 302 | Temporarily moved | Confirm this should not be a 301 | | 403 | Forbidden | Check permissions and access rules | | 404 | Not found | Fix broken links, set up redirects | | 500 | Internal server error | Check application logs immediately | | 502 | Bad gateway | Investigate upstream server health | | 503 | Service unavailable | Check server load or maintenance status |
Understanding HTTP status codes is the first step toward maintaining a reliable website. The second step is making sure you find out about problems before your visitors do, and that is where automated monitoring becomes indispensable.