HTTP status code

An HTTP status code tells browsers and search engines what happened when they requested a page. It is one of the clearest technical signals a server can return. When that code changes unexpectedly, it can affect whether a page is accessible, crawlable, and eligible to appear in search results.

Because this check applies to all pages and a normal live page usually returns 200, any unexpected change deserves attention. Monitoring status codes helps you catch serious technical issues early, before they spread into indexing loss or a poor user experience.

What it is

An HTTP status code is the response a server gives when a page is requested. It is a short numeric code that explains the result of that request.

For example:

• 200 means the page loaded successfully
• 301 or 302 means the page redirects somewhere else
• 404 means the page could not be found
• 500 means there is a server-side error

In this case, SEOlerts is monitoring the final HTTP status code, which means the status returned at the end of the request process. If a page redirects first, the tool focuses on the final outcome rather than only the first step.

Why it matters

Status codes are critical for indexing and accessibility because they tell search engines whether content is available and whether users can reach it.

A 200 status usually means a page is live and accessible. If that changes, search engines may stop treating the page as normal content. A page returning 404, 410, 500, or another unexpected code can quickly lose visibility or become unusable for visitors.

Even redirects matter here. A change from 200 to 301 may be intentional during a migration, but if it happens without planning it can alter how search engines process the page and where ranking signals are passed.

In simple terms, the status code is one of the first technical checks that determines whether a page can do its job at all.

What can go wrong if unchecked

If a page stops returning 200, several problems can follow.

A 404 or 410 may mean the page has been removed, renamed, or broken. A 500 response may point to a server issue, application error, or infrastructure failure. A 403 could mean access has been blocked accidentally. A redirect response may send users and search engines somewhere else entirely.

If these changes go unnoticed, the impact can be severe:

• pages may drop out of the index
• important landing pages may become inaccessible
• internal links may point to broken destinations
• crawlers may waste time on faulty URLs
• users may hit error pages instead of content

Because this applies across the whole site, a status code issue can affect a single page or signal a much larger deployment or hosting problem.

Why monitoring it matters

Monitoring HTTP status codes gives you an early warning when page availability changes. Many serious SEO problems begin with a simple response change that is easy to miss until traffic falls or error reports start building up.

An alert is especially useful after deployments, CMS changes, server updates, CDN rule edits, migrations, or security configuration changes. These are all moments when pages that should return 200 can suddenly begin returning something else.

Since the status code is such a fundamental signal, monitoring it helps you detect technical failures before they become wider indexing and accessibility issues.

What an alert may mean

An alert means the page’s final status code is different from the one previously recorded. In this case, the most important situation is when a page changes away from 200, though any change may still be worth reviewing.

In practice, that could mean:

• the page has been removed or moved
• a redirect has been introduced
• the server is returning an error
• access rules have changed
• the page is blocked by infrastructure or security settings
• a deployment has altered how the URL is handled

Not every change is automatically bad. For example, a planned 301 during a URL migration may be correct. But because status codes directly affect indexing and accessibility, the reason behind the change should be confirmed quickly.

What to check next

First, verify which status code is now being returned and whether the change was intentional.

Then check the likely cause:

• if it is 301 or 302, review the redirect target and confirm it was planned
• if it is 404 or 410, check whether the page was removed, renamed, or linked incorrectly
• if it is 500 or another 5xx, review server logs, application errors, and recent releases
• if it is 403, check access controls, firewall rules, and security settings

It is also useful to check whether the issue affects one page, a section, or the whole site. A single broken URL suggests a page-level issue, while large numbers of changed status codes often point to a broader technical fault.

Finally, review related SEO signals such as internal links, canonicals, sitemaps, and crawl data. A status change rarely exists in isolation.

Key takeaway

The HTTP status code tells search engines and users whether a page is available and how it is being served. Monitoring the final status code is essential because unexpected changes can directly affect indexing, accessibility, and site performance. An alert does not always mean disaster, but it does mean the page’s response has changed and should be checked promptly.