HTTP status codes are three-digit server responses that indicate whether a request was successful, redirected, blocked, or failed. Understanding these codes is essential for diagnosing site issues, managing redirects, and ensuring search engines can crawl and index your content properly.
Every time a browser or bot requests a page, the server sends back a three-digit code before or alongside the content. This code tells the requester what happened: was the page found, moved, forbidden, or did something break on the server side. The first digit defines the class of response. 1xx codes are informational and rare in everyday work. 2xx codes mean success. 3xx codes signal redirection. 4xx codes indicate a client-side problem, often a missing or restricted resource. 5xx codes point to server-side failures. The most common codes you'll see are 200 (success), 301 (permanent redirect), 302 (temporary redirect), 404 (not found), and 500 (internal server error). Each code shapes how browsers render content and how search engines decide whether to crawl, index, or drop a URL from their database.
Search engines rely on status codes to decide what to do with a URL. A 200 tells Google the page is live and should be indexed. A 301 signals that the content has permanently moved, so the engine should transfer ranking signals to the new location and eventually drop the old URL. A 404 means the page is gone, and after repeated crawls, the engine will remove it from results. A 500 error suggests a temporary server problem, so the engine may retry later before deciding whether to deindex. Serving the wrong code can waste crawl budget, lose rankings, or orphan pages. For example, using a 302 instead of a 301 during a site migration can delay or prevent the transfer of authority to new URLs. Similarly, returning 200 for pages that should 404 creates soft-404 problems, where Google sees thin or missing content but the server claims everything is fine.
One frequent error is chaining redirects: URL A redirects to B, which redirects to C. Each hop adds latency and increases the chance that a bot or user abandons the journey. Another mistake is using 302 redirects for permanent moves. Since 302 signals temporary relocation, search engines may not consolidate ranking signals, leaving the old URL in limbo. Some platforms accidentally serve 200 status codes on custom 404 pages because the server renders an error template but doesn't set the response header correctly. This confuses crawlers and wastes resources. On the opposite end, returning 404 for pages that should redirect (like discontinued products with replacement models) throws away existing link equity. Finally, ignoring 5xx errors during high-traffic periods or after deployments can lead to large-scale deindexing if the problem persists across multiple crawl cycles.
Browser developer tools are the quickest way to inspect a single page. Open the Network tab, load the page, and look at the status column for the document request. For bulk checks, crawler tools like Screaming Frog or Sitebulb can audit entire sites and flag non-200 responses. Server logs provide a historical view: parse your access logs to identify patterns of 404s, 5xx spikes, or redirect chains. For ongoing monitoring, uptime services and synthetic monitoring platforms can alert you when critical pages start returning errors. In a site migration or replatforming project, compare a crawl of the old site against the new one to confirm every important URL either returns 200 or redirects with 301 to the correct new location. Automated tests in a staging environment can catch misconfigured redirects or missing error-handling before launch.
Use 301 redirects when you permanently move a page, merge content, or change URL structure. This consolidates authority and tells search engines to replace the old URL with the new one. Use 302 or 307 sparingly, only when you genuinely plan to restore the original URL later—such as a product temporarily out of stock or a page under A/B testing. For deleted content with no replacement, a proper 404 or 410 (gone) is correct. This frees crawl budget and removes the URL from the index cleanly. If a page is restricted by login or paywall, 403 (forbidden) or 401 (unauthorized) is appropriate; these codes tell bots not to expect public access. For temporary server issues, 503 with a Retry-After header signals that the problem is short-lived, reducing the risk of immediate deindexing during maintenance windows.
Content delivery networks, reverse proxies, and serverless architectures can introduce additional layers where status codes are generated or rewritten. A misconfigured CDN might cache a 404 response and serve it to all users, or a reverse proxy might return 502 (bad gateway) when the origin server is unreachable. In these setups, it's critical to trace where each code originates—edge, proxy, or origin—so you can fix the right component. JavaScript-rendered sites add complexity: the initial server response might be 200, but the app could render a not-found state client-side without updating the status code. Implement server-side rendering or dynamic rendering for important pages to ensure bots see accurate status codes. Similarly, API-driven headless CMSs must explicitly set status headers in their responses, as the default is often 200 even when content is missing.
A 301 redirect signals a permanent move, prompting search engines to transfer ranking signals to the new URL and eventually remove the old one from their index. A 302 indicates a temporary redirect, so engines may keep the original URL in the index and not fully consolidate authority. Use 301 for lasting changes like rebranding or URL restructuring, and reserve 302 for short-term situations where you plan to revert to the original address.
This happens when the server renders a not-found template but forgets to set the HTTP response header to 404. The page looks correct to users, but crawlers see a 200 success code, treating it as valid content. This creates soft-404 issues that waste crawl budget and clutter the index. Check your server or CMS configuration to ensure the status header matches the page state.
Google typically retries a 500 error multiple times over a short period, assuming the problem is temporary. If the error persists across several crawl attempts spanning days or weeks, the page may be dropped from the index. Using a 503 status code with a Retry-After header during planned maintenance gives clearer guidance and reduces the risk of premature deindexing.
Yes. Each redirect adds latency, and bots may stop following after several hops, preventing the final URL from being discovered or indexed. Redirect chains also dilute link equity across multiple jumps. Audit your redirects regularly and update them to point directly to the final destination, eliminating intermediate steps wherever possible.
Both tell search engines the page is gone, but 410 explicitly signals the removal is intentional and permanent, which can speed up deindexing. A 404 is interpreted as the resource might return someday. In practice, 404 is more common and works fine for most deletions. Use 410 if you want to communicate finality, such as when removing discontinued product lines or retired landing pages.
Desktop crawlers like Screaming Frog or Sitebulb can audit thousands of URLs and flag non-200 responses, redirect chains, and orphaned pages. For even larger sites, parse server logs to identify status-code patterns over time. Cloud-based tools and automated monitoring can alert you to sudden spikes in 4xx or 5xx errors, helping you catch issues before they impact rankings or user experience.