An SEO’s Guide to HTTP Status Codes (An Infographic) – Moz

HTTP status codes are the internet’s tiny mood rings. They look like three boring digits in a server response, but to an SEO, they can mean the difference between “page indexed beautifully” and “why did our traffic just fall down the stairs?” If you work in technical SEO, site migrations, content pruning, or even basic website maintenance, understanding HTTP status codes is not optional. It is survival with better formatting.

These codes tell browsers, bots, APIs, and search engines what happened when they requested a URL. Did the page load? Move? Vanish? Refuse entry like a nightclub with a dress code? Search engines pay very close attention to these responses because they shape crawling, indexing, canonicalization, and overall site health. A page can have amazing content, killer keywords, and a title tag polished like a sports car, but if the server sends the wrong signal, none of that sparkle matters much.

This guide breaks down the HTTP status codes SEOs care about most, what they actually mean, how Google and Bing tend to interpret them, and which mistakes make technical audits turn into emotional support sessions. Think of it as an infographic in article form: same quick-hit usefulness, fewer arrows, more nuance.

What Are HTTP Status Codes, and Why Should SEOs Care?

HTTP status codes are server response codes. When a browser or search bot requests a URL, the server responds with a code that explains the outcome. For SEO, these responses affect whether search engines can crawl a page, whether they should keep it in the index, whether they should follow a redirect, and whether they should come back later or stop trying.

That matters because crawling is the front door to visibility. If search engines cannot fetch the page properly, they cannot evaluate the content properly. And if they cannot evaluate it, they cannot rank it. Status codes also influence user experience. A broken page, a bad redirect, or a maintenance page returning the wrong response can confuse visitors, waste crawl budget, muddy reporting, and make your analytics look like they need therapy.

In simple terms, status codes are where technical SEO meets reality. Your sitemap, internal links, canonicals, and content strategy all depend on the server saying the right thing at the right time.

The Five Families of HTTP Status Codes

1xx: Informational

These are provisional responses. They usually tell the client, “Hang on, we’re still working on it.” SEOs rarely spend much time here, but some newer codes like 103 Early Hints can matter for performance discussions because they help preload resources earlier. Translation: not the star of your audit, but not totally useless either.

2xx: Success

This is the happy family. A 200 OK means the request worked and content was delivered. Most pages you want indexed should return a 200. But here is the sneaky part: a 200 does not automatically guarantee indexing. It only means the page was successfully fetched. Search engines still decide whether the content deserves to be indexed.

3xx: Redirection

These codes tell clients the requested URL has moved somewhere else. Redirection codes are essential during migrations, URL updates, content consolidation, and replatforming. Done right, they preserve equity and guide users smoothly. Done badly, they create chains, loops, confusion, and the sort of meeting where everyone suddenly loves the phrase “root cause analysis.”

4xx: Client Errors

These codes mean the request could not be completed because the requested resource is unavailable or access is blocked. In SEO land, this often means the URL is not indexable, not useful, or not worth crawling repeatedly. Common examples include 404 Not Found, 410 Gone, 401 Unauthorized, and 403 Forbidden.

5xx: Server Errors

These are the real panic buttons. They signal that the server failed while trying to process a valid request. Search engines usually treat persistent 5xx errors as a sign that the content is temporarily or repeatedly unavailable. That can reduce crawl activity and, over time, cause indexed pages to drop out. If 4xx errors say “this page is gone,” 5xx errors say “this website may be having a rough day.”

The HTTP Status Codes SEOs Need to Know by Heart

200 OK

This is the gold standard for live, indexable pages. A 200 response means the page loaded successfully. Product pages, service pages, blog posts, category pages, and evergreen resources that should rank generally need to return 200. But do not assume all 200s are good. A page can return 200 and still be a soft 404, thin content page, or accidental duplicate. A “successful” response is not the same as a useful one.

301 Moved Permanently

This is your best friend during permanent URL changes. Use a 301 when content has moved for good. It tells search engines to transfer signals and process the destination as the preferred location. Site migrations, HTTP-to-HTTPS moves, trailing slash normalization, and merging duplicate pages often rely on 301 redirects. They are strong signals, and that strength matters.

302 Found and 307 Temporary Redirect

These are for temporary moves. If a page is briefly unavailable due to testing, maintenance, or short-term campaign logic, a 302 or 307 can make sense. The problem is not the code itself. The problem is when teams leave temporary redirects in place for months and then act surprised when search engines start treating the destination like the real thing. Temporary means temporary, not “we’ll revisit this in Q4, maybe.”

308 Permanent Redirect

Think of 308 as the method-preserving cousin of 301. For SEO purposes, it is generally treated similarly to a permanent redirect. Many SEO conversations still center on 301 because it is familiar, but 308 is also valid when the move is permanent and the implementation calls for it.

304 Not Modified

This one does not mean “broken.” It means the content has not changed since the last crawl or fetch, so the client can use the cached version. For SEO, a proper 304 response can help save bandwidth and streamline recrawling, especially when supported by headers like ETag or Last-Modified. It is a quiet efficiency code, not a red flag.

404 Not Found

This is the classic dead-end response. It tells search engines that the requested URL does not currently exist. A 404 is perfectly normal for removed or mistyped URLs. It is not automatically an SEO disaster. The trouble starts when important pages return 404 unexpectedly, when internal links point to 404s at scale, or when your site creates endless broken parameter URLs like a chaos generator.

410 Gone

Use 410 when a page is intentionally and permanently removed with no replacement. It sends a clearer “this is over” signal than a 404. For content pruning, expired promotions, or outdated pages you truly want removed, 410 can be a useful choice. It is basically the status code version of “we wish this page well in its future endeavors.”

401 Unauthorized and 403 Forbidden

These codes matter when content is protected. A 401 means authentication is required. A 403 means access is forbidden. If a page should not be publicly accessible, these are reasonable responses. But they are terrible choices for managing crawl rate. Blocking bots with the wrong intent can create indexing confusion without solving the actual performance problem.

429 Too Many Requests

This code means the client is sending too many requests in a given time window. In SEO, 429 matters because search engines may treat it as a signal that the server is overloaded and temporarily slow crawling. If your site is under heavy strain, 429 can be appropriate in controlled scenarios. But if it becomes common, crawl consistency suffers and diagnostics become much less fun.

500, 502, 503, and 504

These server-side errors can hurt visibility fast when they affect important URLs. A 500 Internal Server Error is a general failure. A 502 Bad Gateway suggests upstream communication trouble. A 503 Service Unavailable is commonly used for temporary overload or planned maintenance. A 504 Gateway Timeout means one server waited too long for another. If you must take a site or section offline temporarily, 503 is typically the smartest response because it clearly says, “not available right now, try again later.” Returning 200 on a maintenance page is like smiling politely while your house is on fire.

How HTTP Status Codes Affect Crawling and Indexing

Search engines do not treat every response equally. Successful 2xx responses allow content to be processed, though not all 200 pages get indexed. Permanent redirects send strong signals that the destination should replace the old URL. Temporary redirects are followed, but they carry weaker long-term intent. Four-hundred-level errors usually mean the page should not remain in the index, while 5xx errors suggest the content may come back later, so crawlers tend to retry before making harsher decisions.

That is why context matters. A 404 on a product discontinued years ago may be fine. A 404 on your money page is not fine. A 302 during a weekend test is fine. A 302 sitting on a high-authority URL for eight months is the SEO equivalent of leaving your turn signal on for three counties.

Google also distinguishes between true 404s and soft 404s. A soft 404 happens when a page returns 200 OK but shows an error message, empty state, or “nothing here” content. Search engines dislike that because the server says success while the page content says failure. It is mixed messaging, and mixed messaging is how indexing reports become comedy.

Common SEO Mistakes With HTTP Status Codes

1. Returning 200 for error pages

This creates soft 404s. If the page is gone, return 404 or 410. If it moved, return 301. Do not serve a cheerful homepage with a 200 and hope the bot figures it out by vibes alone.

2. Using 302s forever

Temporary redirects are not permanent architecture. If the move is permanent, switch to 301 or 308. Otherwise you create ambiguity for search engines and confusion for future teammates who inherit the mess.

3. Redirecting every deleted page to the homepage

This is one of the internet’s most persistent bad habits. If there is a closely relevant replacement, redirect there. If there is not, use 404 or 410. Homepage dumping is rarely helpful for users or crawlers.

4. Ignoring redirect chains and loops

One redirect is manageable. Three, four, or ten in a row is wasteful. Long chains slow crawling, dilute clarity, and annoy users. Loops are even worse because they create broken experiences and incomplete crawling.

5. Serving maintenance pages with 200 OK

If the site is temporarily unavailable, a 503 is usually the right call. That tells crawlers the outage is temporary. A 200 says everything is fine, even when everything is absolutely not fine.

6. Forgetting to monitor status code changes after launches

Redesigns, CMS updates, plugin changes, CDN rules, and JavaScript rendering issues can all alter status codes unexpectedly. Always test before launch and crawl after launch. Hope is not a monitoring strategy.

How to Audit HTTP Status Codes Like an SEO Pro

Start with the basics: check important URLs in your browser’s developer tools, especially the Network tab, to confirm the actual response code of the HTML document. Then crawl the site with an SEO crawler so you can spot patterns, not just single-page issues.

Next, use Google Search Console. The Page Indexing report helps reveal soft 404s, redirect issues, and non-indexed URLs. The Crawl Stats report is useful for understanding how Googlebot interacts with your site over time, including response patterns and host health. That combination gives you both symptoms and behavior.

Then go deeper with server logs if you have access. Logs show how search engines and users are actually hitting URLs in the wild. This is where you catch repeated 404s from internal links, wasted crawl activity on junk URLs, or a spike in 5xx errors after a deployment that “totally should have been fine.”

Infographic-Style HTTP Status Code Cheat Sheet for SEO

Real-World SEO Experiences With HTTP Status Codes

Across technical SEO projects, HTTP status codes often look simple in theory and wildly dramatic in practice. One of the most common experiences happens during site migrations. A team maps old URLs to new ones, launches on schedule, and proudly announces success. Then a crawl reveals that half the important pages are using 302s instead of 301s because someone copied a redirect rule set from staging and never updated the logic. The site still “works,” users still land somewhere, and nobody notices at first. But indexing gets messy, canonical signals take longer to settle, and performance reports become suspiciously moody. That is the kind of issue status code audits catch before the blame game becomes a team sport.

Another common scenario shows up on large ecommerce sites. Filters, faceted URLs, expired products, and internal search pages create thousands of URLs that technically return 200 but behave like dead ends. To a user, the pages say “no results found.” To the server, they say “everything is fantastic.” That mismatch creates soft 404 headaches, wasted crawl activity, and a lot of puzzling non-indexed URLs in Search Console. In practice, cleaning this up usually means deciding which pages deserve real indexable content, which ones should be blocked or canonicalized, and which ones should simply return a proper 404 or 410.

There is also the classic maintenance disaster. A company puts up a pretty maintenance page during an outage, complete with branding, apology copy, and maybe an inspiring stock photo of a sunrise. Very nice. Very polished. Also returning 200 OK. Search engines now see a fully successful page with thin duplicated content instead of a temporary outage. The better move is a 503 response, ideally with a sensible retry window, so crawlers understand the downtime is temporary. This is one of those technical details that feels tiny until it becomes expensive.

Content pruning offers a more satisfying experience when done correctly. Suppose a publisher removes hundreds of outdated, low-value articles with no meaningful replacement. Redirecting everything to a broad category page sounds tidy, but it often creates relevance problems. In many real audits, the cleaner solution is to use 410 for content that is truly gone, 301 only where there is a close substitute, and then update internal links so the site architecture reflects reality. That combination tends to reduce clutter, improve crawl focus, and make reporting much easier to interpret.

Finally, status codes become especially important when multiple teams touch the same stack. SEO wants one thing, development wants another, DevOps is watching uptime, and product is trying to ship before lunch. In that environment, HTTP status codes become shared language. They help everyone understand whether a page is live, moved, removed, blocked, overloaded, or simply misconfigured. When teams align on those signals early, launches go smoother. When they do not, the audit eventually arrives like an invoice from the universe.

Conclusion

HTTP status codes are not just developer trivia. They are core SEO signals that affect crawling, indexing, user experience, and site maintenance. The right code helps search engines understand your intent. The wrong code creates ambiguity, waste, and ranking friction. A page that should rank usually needs a solid 200. A permanent move should use 301 or 308. A removed page should not fake being alive with a 200. A temporary outage should not pretend everything is normal.

If you remember one thing, make it this: status codes should match reality. When the server tells the truth, search engines work more efficiently, users get cleaner experiences, and technical SEO becomes a lot less dramatic. Which is good, because there is already enough drama on the internet.