13 Common HTTP Status Codes + Explanations

13 Common HTTP Status Codes + Explanations
Encountering certain HTTP status codes on your website isn't necessarily a drawback; often, it's just a sign of room for improvement. So, understanding HTTP status codes and how they influence your website’s operations, visibility, and success is crucial.

The goal isn't to memorize all the codes (although kudos to you if you do). But to understand the purpose the most important and common HTTP status codes serve and how to deal with them for optimal website performance is one of the keys to success.

You can find all answers in this article to what an HTTP response status code means, the most common HTTP status codes that every SEO person must know, and how to monitor them.

What are HTTP Status Codes?

HTTP, which stands for Hypertext Transfer Protocol, is the foundation of any data exchange on the web. In simple terms, it's the language that web servers and clients (like your web browser) use to communicate with each other.

An HTTP status code, as the name implies, is a three-digit code that a server sends in response to a client's request. The HTTP code indicates whether the request was successful or if there were any errors. 

some of the most common http status codes

Not only do HTTP status codes form a vital part of web browsing, but they're critical for maintaining an SEO-friendly website.

When you enter an URL or click on a link, the browser shoots off a request to the server. The server, in return, attempts to locate the resource the browser is asking for and responds with an HTTP status code. The browser interprets this code, displays its corresponding message to the user or follows the instructions it signifies.

Sounds straightforward enough, right?

But here's the catch: there are more than 40 different HTTP status codes! Each one corresponds to a specific situation, providing a glimpse into how search engines and users interact with our websites.

The Most Common and Important HTTP Response Status Codes

HTTP response status codes are divided into five different categories, each representing a different kind of response. Here’s a brief lowdown on each:

Status Code Category Description
100 Informational Continue - The initial part of the request has been received and the client should continue with the request.
101 Informational Switching Protocols - The server is changing protocols as requested by the client.
200 Success OK - The request was successful.
201 Success Created - The request has been fulfilled and a new resource has been created.
301 Redirection Moved Permanently - The requested page has been permanently moved to a new URL.
302 Redirection Found - The requested page has been found, but it's temporarily located at a different URL.
304 Redirection Not Modified - The client's cached version of the requested resource is still valid.
400 Client Error Bad Request - The server cannot process the request due to a client error (e.g., malformed request syntax).
401 Client Error Unauthorized - The request requires user authentication.
404 Client Error Not Found - The requested resource could not be found on the server.
410 Client Error Gone - The requested resource is no longer available at the server and no forwarding address is known.
500 Server Error Internal Server Error - An unexpected condition prevented the server from fulfilling the request.
501 Server Error Not Implemented - The server does not support the functionality required to fulfill the request.

ℹ️ Informational Responses (1xx)

The 1xx status codes are all about information. These are provisional responses that show that the request is received and is being processed.

These status codes are rarely visible to the end-user because they're basically the server and client exchanging information with each other. Still, they can occasionally trigger actions in browsers or other clients.

The Most Common 1xx Status Codes

  • 100 Continue: By far the most common 1xx code. The server is telling the client everything is good, and you can continue with your request.
  • 101 Switching Protocol: The client has asked to use a different protocol (like switching from HTTP 1.1 to HTTP 2), and the server has accepted.

✅ Successful Responses (2xx)

Let's start with the golden star of status codes: What does a 2xx successful status code mean?

The Most Common 2xx Status Codes

  • 200 OK: The request has been successful. This is the standard response for a successful HTTP request.
  • 201 Created: This lets you know that a new resource was successfully created as a result of the request. It's commonly used in response to a POST or some PUT requests.

↪️ Redirection Status Codes (3xx)

Redirects are an ordinary and often necessary part of using the web and building an SEO-friendly site. With the right use of redirects, we can ensure that our users and Google can find our most important pages, even if the URLs change over time. Here are some of the most critical ones you should understand:

The Most Common 3xx Status Codes:

301 - Permanent Redirect: The 301 Status Code indicates that the URL resource has been moved to a different address permanently. This tells search engines and users that this page isn’t coming back. Thus, they should update their records and not try to access the old URL again.

302 - Temporary Redirect: 302 Status Code suggests a temporary move of a URL. It says to Google "Hey, don't worry about updating the URL in your index, because we'll be back at our old location soon". Keep in mind, making improper use of this code (like using it for a permanent move) can lead to all sorts of SEO problems!

304 - Not Modified: The 304 Status Code is like a polite little nod from your server to browsers and search engines. They’re essentially saying, "Hey, you already have the updated content, so no need for me to resend everything again". Such status codes can help speed up the user experience.

Might you have seen redirection happening when browsing? 3xx HTTP Status codes tell us that further action is needed, usually in the form of URL redirection.

These codes tell you that the resource you’re looking for isn’t available at the requested URL, but it is somewhere else.

🔎You may want to read: How to Detect 3xx Redirect Chain

⚠️ Client Error Status Codes (4xx)

Sometimes, your users or search engines might encounter errors on your website. It's essential to know which commonly seen error codes indicate and how to fix them.

The Most Common 4xx Status Codes:

400 - Bad Request: Encountering a 400 Status Code indicates that the server could not understand the request due to bad syntax. If you identify this code in your server logs or SEO tools, you'll need to investigate it further.

401 - Unauthorized Error: The 401 Status Code is displayed when the server needs to verify the user's credentials. This isn't SEO-negative per se, but it's good to ensure such pages aren't being indexed.

403 - Forbidden: A 403 Status Code indicates that the request was valid, but the server is refusing action. This can occur when specific levels of login are required to access a page.

404 - Not Found: If you've been anywhere near SEO, you're probably well-acquainted with the 404 Status Code. It simply means that the requested data does not exist on the server. These can occur when people try to request URLs that don't exist, sometimes because they typed the URL wrong, or the page has been deleted.

410 - Gone: The code 410, commonly known as the "410 error" in HTTP status, signifies that the requested URL has been permanently deleted. In simpler terms, the URL used to exist, but it was deliberately removed and won't come back.

4xx codes tend to spell trouble. They mean the request contains incorrect syntax or couldn't be fulfilled.

These are cases where the request is syntactically valid, but due to some error on the client's side, it can't be fulfilled.

⛔ Server Error Status Codes (5xx)

Server error status codes indicate that the server knows it has errored out or is incapable of delivering the requested resource.

Just as the 4xx block of codes are client errors, 5xx codes are indicative of server-side errors.

The Most Common 5xx Status Codes:

500 - Internal Server Error: The 500 Status Code is a very general error response indicating that something has gone wrong on the website's server, but it's unclear what the specific problem is.

501 - Not Implemented: The 501 Status Code indicates that the server either does not recognise the request method or is unable to fulfill the request. This usually happens due to technical problems on the website's server.

Understanding these common HTTP status codes can greatly help in identifying the problem areas and enhancing overall site performance.

Why HTTP Status Response Codes are Important for Web Performance?

Operating in today's digital world, the competition is fierce, and your site's performance has a substantial impact on your SEO ranking. Not only that, but your website's speed and reliability are crucial elements influencing user experience and, therefore, your site's traffic and conversions.

Moreover, regular monitoring can help us quickly identify any abnormal response - whether that's a sudden influx of traffic or an unexpected error. Just like any physical business, you're working to cater to your audience's needs, and any disruptions, delays, or errors can be damaging.

Long story short: regular monitoring is your site's best friend. It's the first line of defense when things go sideways; it helps you anticipate problems and facilitates superior performance that boosts SEO significantly. 

For this aim, you can conduct an SEO audit regularly to see if your website needs improvements regarding HTTP headers and other technical aspects. However, if you need to check only a web page, there is no need to run a complete SEO audit; you can use online HTTP status checker tools.

How to Check HTTP Status Codes with SEOmator?

Fortunately, we live in an era of brilliant technology where countless monitoring tools are available to assist us. 

SEOmator’s Free HTTP Header & Status Checker Tool checks the HTTP response code of your web page and provides insights on improving the user experience and search engine visibility.

Here are the steps to detect HTTP status codes of web pages by using SEOmator’s well-reviewed and powerful tool:

Step 1 - Go to SEOmaor’s Free HTTP Header & Status Checker Tool.
SEOmator's HTTP status checker tool
Step 2 - Enter a web page into the search bar and click “Submit”.
http response code checking
Step 3 - The tool will analyze the header response of your web page and provide a detailed report.
http status code checking result page


SEO is a lot more technical than what meets the eye. It's a world that merges with the technical operation of a website, and common HTTP status codes form a critical component of this aspect. This comes as no surprise, considering how often Google reiterates the importance of a well-functioning website for rankings.

So to put it simply, HTTP status codes matter. They matter when a user tries to access your site, they matter for your website's functioning, and they certainly matter for your SEO.

Being aware of the different types of HTTP status codes helps you understand what's going on under the hood of your website. It illuminates whether requests to your website are successful, whether pages have moved and if errors are restricting content from being accessed.

While dealing with HTTP status codes can feel overwhelming due to their technicality, don’t forget that the entire purpose of these codes is to help - not hinder. They're there to inform us about what's going on with our website, to help us recognize when something goes wrong and to guide us in fixing issues promptly.

In the future, as technology and SEO practices advance, we might witness more developments in how HTTP status codes function, how search engines interpret them, and how they integrate with our existing SEO strategies. 

Meaning, the more you keep abreast of these developments, the more adept you'll be at adapting to changes and maintaining an SEO-friendly site!

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