HTTP Status Codes and Their Meaning: The Complete List Every Site Owner Needs

If you’ve ever run a crawl on your website and been greeted by a wall of three-digit numbers, you know the feeling. What do they all mean? Which ones are fine, and which ones are quietly killing your rankings? This complete list of HTTP status codes and their meaning will give you clarity, plus the practical SEO knowledge to act on what you find.

I’m Jim from Best SEO, and I’ve spent years auditing Singapore websites where a handful of mismanaged status codes were responsible for 30-40% drops in organic traffic. These aren’t just technical trivia. They’re the language your server speaks to Google, and if your server is saying the wrong things, your rankings pay the price.

Let’s walk through every status code class, what each code means, and exactly what you should do when you encounter them.

1xx Informational Responses

These codes are handshake signals between the browser and server. They confirm that the initial part of a request was received and the server is ready for more. You’ll rarely see these in your crawl reports or server logs, but understanding them helps you grasp how HTTP communication actually works.

• 100 Continue: The server received the request headers and is telling the client to go ahead and send the request body. This is common with large POST requests where the client checks first before transmitting a big payload.
• 101 Switching Protocols: The server agrees to switch to a different protocol as requested by the client. You’ll see this when a connection upgrades from HTTP to WebSocket, which is common in real-time chat applications.
• 102 Processing (WebDAV): The server is working on the request but has no response ready yet. This prevents the client from timing out during long operations.
• 103 Early Hints: This one is increasingly relevant for performance. It allows the server to send preliminary headers (like preload directives for CSS or fonts) before the final response. Google Chrome supports this, and it can shave 100-500ms off perceived load times.

SEO Impact of 1xx Codes

Practically zero. Googlebot handles these transparently. But if you’re a developer working on site speed optimisation, 103 Early Hints is worth implementing. Faster page loads mean better Core Web Vitals scores, which is a confirmed ranking signal.

2xx Successful Responses

This is the class you want to see most often. A 2xx code means the server received, understood, and successfully processed the request. When Googlebot gets a 200, it knows the page is alive and ready to be indexed.

• 200 OK: The gold standard. The request succeeded and the server returned the requested content. Every indexable page on your site should return this.
• 201 Created: A new resource was successfully created. You’ll see this in API responses after a successful POST request, like when a user submits a form that creates a new account.
• 202 Accepted: The request was accepted for processing, but the processing isn’t finished yet. Think of it like placing an order at a hawker stall. The uncle has acknowledged your order, but your char kway teow isn’t ready.
• 203 Non-Authoritative Information: The response came from a cached or third-party copy, not the origin server. The data is valid but might not be the freshest version.
• 204 No Content: The server processed the request successfully but isn’t sending any content back. Common after a DELETE operation or when saving preferences via AJAX.
• 205 Reset Content: Similar to 204, but it also tells the client to reset the document view. Useful for clearing form fields after a successful submission.
• 206 Partial Content: The server is delivering only a portion of the resource because the client requested a specific range. This is how video streaming and large file downloads work, sending content in chunks.
• 207 Multi-Status (WebDAV): The response body contains multiple status codes for multiple sub-requests, formatted as XML.
• 208 Already Reported (WebDAV): Prevents the server from listing the same resource multiple times in a multi-status response.
• 226 IM Used: The server fulfilled a GET request and the response represents the result of instance-manipulations applied to the current resource. Rarely encountered in practice.

SEO Impact of 2xx Codes

The 200 status code is the foundation of your entire SEO strategy. If your important pages aren’t returning 200, they’re not getting indexed properly. One issue I see frequently on Singapore e-commerce sites is “soft 404s”, where a page returns a 200 OK status but actually displays a “product not found” message. Google has gotten better at detecting these, but they still waste crawl budget and confuse your site’s indexing signals.

Run a crawl with Screaming Frog or Sitebulb and filter for 200 responses. Then manually check a sample of those pages to confirm they’re actually serving real content.

3xx Redirection Messages

Redirects tell the browser (and Googlebot) that the content has moved somewhere else. This is where many Singapore businesses get into trouble, especially during site migrations or platform changes.

• 300 Multiple Choices: The request has more than one possible response, and the user or user agent should choose one. Rarely used in practice.
• 301 Moved Permanently: The resource has permanently moved to a new URL. This is the redirect you should use for SEO because it passes approximately 95-99% of link equity to the destination URL.
• 302 Found: A temporary redirect. The client should continue using the original URL for future requests. Google treats 302s differently from 301s. If you accidentally use a 302 when you mean a 301, Google may keep the old URL in its index instead of replacing it with the new one.
• 303 See Other: Tells the client to retrieve the resource at a different URL using a GET request. Common after form submissions to prevent duplicate submissions on refresh.
• 304 Not Modified: The resource hasn’t changed since the last request. The browser can use its cached version. This is great for performance because it saves bandwidth and speeds up page loads.
• 305 Use Proxy (Deprecated): No longer in active use.
• 306 Switch Proxy (Deprecated): No longer in active use.
• 307 Temporary Redirect: Like a 302, but it guarantees the HTTP method won’t change. If the original request was a POST, the redirected request will also be a POST.
• 308 Permanent Redirect: Like a 301, but it guarantees the HTTP method won’t change. Useful for API endpoints where you need to preserve the request method during a permanent move.

SEO Impact of 3xx Codes

Redirect chains are one of the most common technical SEO problems I find on Singapore websites. A redirect chain is when URL A redirects to URL B, which redirects to URL C, which finally reaches URL D. Each hop dilutes link equity and slows down crawling. Google will follow up to 10 redirects in a chain, but best practice is to keep it to one hop.

Here’s what to do. Audit your redirects quarterly. Look for chains longer than one hop and flatten them so every old URL points directly to the final destination. Also check that you’re using 301s (not 302s) for any permanent moves. I once worked with a Singapore property portal that had 4,200 pages on 302 redirects instead of 301s. Switching them recovered 23% of their lost organic traffic within six weeks.

4xx Client Error Responses

These codes mean the problem is on the client’s side. The request was malformed, unauthorised, or pointed at something that doesn’t exist. For SEO, the 4xx class is where most of your crawl budget gets wasted.

• 400 Bad Request: The server can’t process the request because of a client-side error, like malformed syntax or an invalid request.
• 401 Unauthorized: The request requires authentication. The client needs to provide valid credentials.
• 402 Payment Required: Reserved for future use. Some APIs use it for billing-related access control, but it has no standard implementation.
• 403 Forbidden: The server understands the request but refuses to authorise it. Unlike 401, re-authenticating won’t help. The client simply doesn’t have permission.
• 404 Not Found: The server can’t find the requested resource. This is the most common error code you’ll encounter, and the one with the biggest SEO implications.
• 405 Method Not Allowed: The HTTP method used (GET, POST, PUT, etc.) isn’t supported for this resource.
• 406 Not Acceptable: The server can’t produce a response matching the client’s Accept headers.
• 407 Proxy Authentication Required: Similar to 401, but authentication must happen with a proxy.
• 408 Request Timeout: The server timed out waiting for the client to finish sending the request.
• 409 Conflict: The request conflicts with the current state of the resource. Common in version control or concurrent editing scenarios.
• 410 Gone: The resource has been permanently removed and will not return. This is different from 404. A 410 tells Google to deindex the page faster because you’re confirming it’s gone for good.
• 411 Length Required: The server needs a Content-Length header that wasn’t provided.
• 412 Precondition Failed: A condition set in the request headers wasn’t met by the server.
• 413 Payload Too Large: The request body exceeds the server’s size limits.
• 414 URI Too Long: The URL is longer than the server can handle. This sometimes happens with excessively parameterised URLs on filtering pages.
• 415 Unsupported Media Type: The server doesn’t support the media format of the request body.
• 416 Range Not Satisfiable: The requested byte range can’t be fulfilled.
• 417 Expectation Failed: The server can’t meet the requirements of the Expect header.
• 418 I’m a teapot: An April Fools’ joke from 1998 (RFC 2324). The server refuses to brew coffee because it’s a teapot. Still in the spec. Still makes developers smile.
• 421 Misdirected Request: The request was sent to a server that can’t produce a response for it.
• 422 Unprocessable Entity (WebDAV): The request was syntactically correct but contained semantic errors.
• 423 Locked (WebDAV): The resource is locked.
• 424 Failed Dependency (WebDAV): The request failed because a previous related request failed.
• 425 Too Early: The server won’t process a request that might be replayed, as a protection against replay attacks.
• 426 Upgrade Required: The server requires the client to switch to a different protocol.
• 428 Precondition Required: The server requires the request to include conditional headers to prevent conflicts.
• 429 Too Many Requests: Rate limiting. The client has sent too many requests in a given time window. This is important for SEO because if Googlebot triggers 429 responses, it will slow down its crawl rate for your site.
• 431 Request Header Fields Too Large: The server won’t process the request because the headers are too large. Often caused by oversized cookies.
• 451 Unavailable For Legal Reasons: The content can’t be served due to legal restrictions. Named after Ray Bradbury’s Fahrenheit 451.

SEO Impact of 4xx Codes

The 404 is the one you need to actively manage. A few 404s are normal and won’t hurt your rankings. Google’s John Mueller has confirmed this. But hundreds or thousands of 404 errors, especially on pages that used to have backlinks or traffic, represent a serious loss of SEO value.

Here’s my recommended workflow for handling 404s:

1. Export all 404 URLs from Google Search Console under the “Pages” report.
2. Check each URL for existing backlinks using Ahrefs or Semrush.
3. If the URL has backlinks, set up a 301 redirect to the most relevant live page.
4. If the URL has no backlinks and no traffic history, leave it as a 404 or upgrade it to a 410 to speed up deindexing.
5. Build a custom 404 page with a search bar, links to your top categories, and a friendly message. Don’t just show a blank error.

For Singapore businesses running e-commerce sites, product pages going 404 after items are discontinued is a constant issue. If you sell out of a product permanently, redirect that URL to the parent category page rather than letting it 404.

5xx Server Error Responses

These are the scary ones. A 5xx code means something went wrong on the server side, and it’s not the user’s fault. For SEO, 5xx errors are urgent because they tell Google your site is unreliable.

• 500 Internal Server Error: A generic catch-all error. Something broke on the server, but the server can’t be more specific about what.
• 501 Not Implemented: The server doesn’t support the functionality required to fulfil the request.
• 502 Bad Gateway: The server, acting as a gateway or proxy, received an invalid response from an upstream server. Common when your CDN or reverse proxy can’t reach your origin server.
• 503 Service Unavailable: The server is temporarily unable to handle requests, usually due to maintenance or overload. This is the correct code to use during planned downtime because it tells Googlebot to come back later rather than deindexing your pages.
• 504 Gateway Timeout: The server, acting as a gateway, didn’t receive a timely response from the upstream server. If you’re on shared hosting in Singapore and your site gets a traffic spike, this is often the result.
• 505 HTTP Version Not Supported: The server doesn’t support the HTTP version used in the request.
• 506 Variant Also Negotiates: An internal server configuration error related to content negotiation.
• 507 Insufficient Storage (WebDAV): The server doesn’t have enough storage to complete the request.
• 508 Loop Detected (WebDAV): The server found an infinite loop while processing the request.
• 510 Not Extended: The server needs additional extensions to the request before it can fulfil it.
• 511 Network Authentication Required: The client needs to authenticate to access the network. You’ve seen this at Changi Airport or Starbucks when you connect to Wi-Fi and get redirected to a login page.

SEO Impact of 5xx Codes

Repeated 5xx errors will cause Google to reduce your crawl rate and can lead to temporary deindexing. I’ve seen this happen to a Singapore F&B chain whose hosting provider had intermittent 502 errors every evening during peak hours. Their organic traffic dropped 34% over two months before they identified the cause.

Here’s what to do if you spot 5xx errors in your server logs or Google Search Console:

1. Check if the errors are intermittent or constant. Intermittent 5xx errors often point to resource limits on your hosting plan.
2. Review your server error logs (not just your access logs) for the specific error messages.
3. If you’re on shared hosting and hitting resource limits regularly, it’s time to upgrade to a VPS or dedicated server.
4. For planned maintenance, always return a 503 with a Retry-After header. This tells Googlebot exactly when to come back.
5. Set up uptime monitoring with a tool like UptimeRobot or Pingdom so you’re alerted within minutes of downtime.

How HTTP Status Codes Directly Affect Your SEO Performance

Now that you know what each code means, let’s connect the dots to your search rankings. HTTP status codes affect SEO through three main channels: crawl budget efficiency, link equity flow, and user experience signals.

Crawl Budget and Indexing Efficiency

Google allocates a crawl budget to every site. For a small business site with 50 pages, this isn’t a concern. But if you’re running a Singapore marketplace or directory with thousands of pages, every wasted crawl on a 404 or 5xx page is a missed opportunity for Google to discover and index your important content.

Clean up your status codes and you’ll see faster indexing of new pages. I’ve measured this directly. One client’s new blog posts went from taking 8-12 days to get indexed down to 2-3 days after we resolved 1,800 redirect chains and 600 soft 404s.

Link Equity Preservation

Every backlink pointing to a 404 page is wasted link equity. If you’ve earned links from The Straits Times, HardwareZone, or any authoritative Singapore domain, and those links point to pages that no longer exist, you’re leaving ranking power on the table. A 301 redirect recovers most of that value.

User Experience and Bounce Rate

A visitor who hits a 404 or a 500 error is very likely to leave. Google measures engagement signals like this. If users consistently bounce from your site after encountering errors, it sends a negative quality signal that can suppress your rankings over time.

A Practical Status Code Audit Checklist

Here’s the exact process I use when auditing HTTP status codes for our clients at Best SEO:

1. Crawl your entire site with Screaming Frog, Sitebulb, or Ahrefs Site Audit. Export all URLs grouped by status code.
2. Fix all redirect chains. Every redirect should be a single hop from source to final destination.
3. Convert accidental 302s to 301s for any permanent URL changes.
4. Audit all 404 pages for lost backlinks. Redirect any with link equity to relevant live pages.
5. Implement 410 for intentionally removed content that you never want indexed again.
6. Check for soft 404s in Google Search Console under Indexing > Pages. These are pages returning 200 but displaying error content.
7. Monitor 5xx errors weekly. Set up alerts so you catch server issues before Google does.
8. Build a custom 404 page with navigation, a search bar, and links to your most important pages.

Do this quarterly, and you’ll keep your site’s technical health in strong shape.

Suggested Internal Links

• Link to the SEO audit service page when mentioning site audits or crawl budget.
• Link to a technical SEO or site migration guide if one exists on bestseo.sg.
• Link to the “What is SEO” page when referencing search engine optimisation fundamentals.
• Link to a page speed or Core Web Vitals article when discussing 103 Early Hints or server response times.
• Link to the contact page in the CTA section.

Stop Guessing, Start Auditing

Understanding HTTP status codes and their meaning is one of those foundational skills that separates website owners who react to problems from those who prevent them. Every code your server returns is a message to Google about your site’s reliability, structure, and trustworthiness.

If you’ve read this far and realised your site probably has redirect chains, orphaned 404s, or intermittent 5xx errors you haven’t investigated, you’re not alone. Most sites do. The difference is whether you fix them before they cost you rankings.

We run detailed technical SEO audits at Best SEO that cover every status code on your site, along with actionable recommendations you can hand straight to your developer. If you’d like us to take a look, request a free SEO audit here or drop us a message. No pressure, just a clear picture of where your site stands.