HTTP Status Codes for SEO: The Complete Reference (2xx–5xx)

A server’s response code is its first word in a conversation with a crawler. Understanding HTTP status codes for SEO isn’t optional; it’s fundamental. This guide cuts the fluff.

What Are HTTP Status Codes and Why Should SEOs Care?

Let’s be direct. An HTTP status code is the server’s three-digit response to a browser’s or crawler’s request for a page. It’s a simple acknowledgement: ‘I got your request, and here’s what happened.’

For a user, this is often invisible. For an SEO, it’s everything. These codes dictate whether search engine bots can access, crawl, and index your content, or if they hit a wall and waste your crawl budget.

Ignoring the nuances of HTTP status codes for SEO is like a mechanic ignoring the check engine light. You might get away with it for a while, but eventually, the entire engine will seize. This reference covers the codes that matter most, from the successful 2xxs to the disastrous 5xxs.

2xx Success Codes: The Goal (Mostly)

When you request a URL and everything works, the server sends back a 2xx status code. This is the digital equivalent of a thumbs-up. It’s what you want to see for all your important, indexable pages.

The most common, and the one you should see 99% of the time, is the 200 OK. It means the server found the file, everything is fine, and here is the content. Congratulations, your server performed its most basic function.

You might occasionally encounter a 204 No Content. This means the server successfully fulfilled the request but there’s no content to send back. It’s often used for tracking pixels or requests where the browser shouldn’t navigate away from the current page. It’s not an error, but you wouldn’t expect to see it on a standard HTML page.

Other 2xx codes like 201 Created or 202 Accepted are rare in typical SEO audits. If you see them, it’s usually related to API interactions. For your core pages, 200 OK is the only status you should be aiming for.

3xx Redirection Codes: The Good, The Bad, and The Ugly

Redirects are a necessary part of web maintenance. They guide users and bots from an old URL to a new one. But using the wrong type of redirect is a classic, unforced error that can kneecap your SEO efforts.

The 301 Moved Permanently is your workhorse. It tells search engines that a page has moved for good and that all link equity and ranking signals should be passed to the new URL. Use it for site migrations, HTTP to HTTPS changes, and permanently consolidating duplicate content.

The 302 Found and 307 Temporary Redirect are for temporary moves. Think A/B testing, device-specific URLs, or promoting a short-term sale. The problem is, developers often use 302s as a default, which tells search engines not to pass link equity because the move isn’t permanent. This is a massive, yet common, mistake.

Worse than a single incorrect redirect is a series of them. Redirect chains and loops burn crawl budget and dilute link equity with every hop. A crawler like ScreamingCAT is essential for spotting these at scale; trying to find them manually is a fool’s errand.

4xx Client Errors: It’s Not Me, It’s You (And It’s Your Problem)

A 4xx status code means the server is fine, but the client—the browser or bot—made a mistake. The request couldn’t be fulfilled. While technically a ‘client’ error, it’s almost always your responsibility to fix the underlying issue on your site.

The infamous 404 Not Found means the server can’t find the requested URL. This happens with deleted pages or typos in links. A few 404s are normal, but a large number, especially from internal links, signals a poor user experience and wasted crawl budget. You need to find and fix your broken links by either removing them or redirecting them to a relevant page.

A 410 Gone is a more definitive 404. It says, ‘This page used to be here, but now it’s gone forever. Don’t come back.’ This is a stronger signal to Google to de-index a URL. Use it when you intentionally remove content and have no suitable replacement to redirect to.

Then there’s the ‘Soft 404’. This is a deceptive, indexable 200 OK page that tells the user ‘Not Found’. It’s the worst of both worlds: users get an error page, and search engines may index a useless, thin-content URL. Fixing soft 404s is critical for site hygiene.

Other common 4xx errors you should be aware of include:

• 400 Bad Request: The server couldn’t understand the request due to malformed syntax.
• 401 Unauthorized: The request requires user authentication. You might see this if your crawler doesn’t have login credentials for a staging site.
• 403 Forbidden: The server understood the request but refuses to authorize it. This can happen if your `robots.txt` or server settings are blocking crawlers.
• 429 Too Many Requests: The user has sent too many requests in a given amount of time. If Googlebot sees this, it will slow down its crawl rate.

5xx Server Errors: It’s Not You, It’s Me (And It’s a Huge Problem)

If 4xx errors are a problem, 5xx errors are a crisis. A 5xx code means your server failed to fulfill a valid request. It’s a direct signal to search engines that your site is unreliable, and if it persists, they will de-index your pages to avoid sending users to a broken site.

The 500 Internal Server Error is the most generic and frustrating. It’s a catch-all for ‘something went wrong on the server, and I don’t know what.’ This could be a database connection issue, a buggy script, or a resource limit being hit. It requires immediate investigation by a developer.

The 503 Service Unavailable is the ‘smart’ server error. It tells crawlers, ‘The server is down for maintenance or is overloaded right now. Please come back later.’ This is the correct code to use during planned site updates. You can even include a `Retry-After` header to tell Googlebot exactly when to return.

Using a 503 for maintenance is a professional move. It preserves your rankings and tells search engines not to panic. Here’s how you might implement a temporary 503 redirect in your `.htaccess` file during a maintenance window:

RewriteEngine On
RewriteCond %{REMOTE_ADDR} !^123.456.789.000
RewriteCond %{REQUEST_URI} !^/maintenance.html$
RewriteRule ^.*$ /maintenance.html [R=503,L]
Header set Retry-After "3600"

Persistent 5xx errors are one of the fastest ways to get your pages de-indexed. Monitor your server logs and Google Search Console’s Coverage report religiously.

Every Experienced Technical SEO

How to Systematically Audit HTTP Status Codes for SEO

You can’t fix what you can’t find. Manually checking status codes is impossible for any site larger than a business card. You need a crawler, and since ScreamingCAT is a free, open-source crawler built in Rust, it’s absurdly fast and efficient for this exact task.

To perform an audit, you simply enter your domain and start the crawl. ScreamingCAT will request every internal URL it finds, just like Googlebot, and record the server’s response.

Once the crawl is complete, navigate to the ‘Internal’ report. The ‘Status Code’ column tells you everything you need to know. You can sort by this column to group all your 3xx, 4xx, and 5xx responses together. From there, you can analyze the ‘Inlinks’ for any given URL to find and fix the source of the problem.

This is the core workflow for any technical SEO audit. By regularly crawling your site and analyzing the HTTP status codes, you can proactively manage your site’s health, protect your crawl budget, and ensure both users and search engines have the best possible experience.