[Error Codes]

HTTP status codes information allows you to quickly reference codes, understand what is happening on the backend of a website, determine what errors need to be fixed, and identify ways to optimize the site for improved SEO.

To help you quickly reference the most important HTTP status codes, we created an HTTP error codes PDF for you to download. We also created a guide to supplement the HTTP status codes cheat sheet and help you identify what each HTTP status code means and which we think are most relevant to SEO.

What are HTTP status codes?

The most common HTTP status codes

Understanding HTTP status organization

HTTP status codes

1xx Status Codes: Information Request

2xx Status Codes: Success

3xx Status Codes: Redirection

4xx Status Codes: Client Error

5xx Status Codes: Server Error

What Are HTTP Status Codes?

HTTP or Hypertext Transfer Protocol is the standard protocol that defines how messages are formatted and sent across the web. HTTP status codes are sets of numbers that explain what is happening during the transfer process between the client (or the browser) and the server.

The codes are sometimes referred to as browser error codes or internet error codes when they indicate that a website won’t load properly.

You don’t need to know every HTTP status code, but there are important HTTP status codes you must be familiar with to avoid SEO problems. A few of the most common codes are:

HTTP status code 404: when a server cannot locate a resource or URL

HTTP status code 400: when a server cannot process a request due to invalid syntax

HTTP status code 500: when a server can’t fulfill a request and doesn’t have information on the specific problem

Our HTTP status codes cheat sheet lists more than 60 codes, and our guide explains the codes we feel are most relevant to SEO and the status of a website.

Understanding HTTP Status Organization

The value for each HTTP status code is not random. The first number in each code helps categorize the code into a specific situation or problem.

1xx Status Codes: Information Request

2xx Status Codes: Success

3xx Status Codes: Redirection

4xx Status Codes: Client Error

5xx Status Codes: Server Error

Knowing the structure of HTTP status codes helps you quickly understand its general nature. By looking at the first number, you can get an idea about what the code implies. But to help you fully understand each code and the exact situation, we’ve compiled this HTTP status codes cheat sheet.

HTTP Status Codes 

1xx Status Codes: Information Request

1xx HTTP status codes indicate that a server is processing information and hasn’t fully completed the request yet. Most 1xx status codes are not directly relevant to SEO situations.

100 – Continue: The client request is good and processing.

101 – Switching Protocol: The client requested to change the type of protocol, and the server agreed.

102 – Processing: Processing is taking a longer time than normal.

2xx Status Codes: Success

2xx HTTP status codes show that a request has been completed and the transfer happened as planned. 2xx status codes aren’t incredibly relevant to SEO other than showing that things are working as they should.

200 – OK: The exchange between the client and the server is complete. Everything is set up properly and nothing should negatively impact SEO.

201 – Created: The client created something (such as a new page) successfully on the server.

202 – Accepted: The client requested to create something on the server. It was accepted, but it has not been completed.

203 – Non-Authoritative Information: Information was transmitted, but it was not taken from the primary source.

204 – No Content: The request was received, but there was no data sent to the client.

205 – Reset Content: Similar to 204, the request was received and there was no data sent to the client, but the response also includes a request to update the content.

206 – Partial Content: Only a portion of the header content was sent to the client.

207 – Multi-Status: The server passed the results of several independent operations at once, which are placed in the body of the message as an XML document.

3xx Status Codes: Redirection

3xx HTTP status codes indicate that the client has requested information that is no longer at the provided address. These are often referred to as redirect codes and they are very relevant to marketers because they impact visitor experience and SEO performance.

For example, if a visitor requests content that has moved, sending them to a 404-page is a bad experience. Redirection allows you to send visitors to relevant content that actually exists. Further, it helps search engines understand what content is available on your site and communicates how you want them to crawl and index it. Both of these variables impact your long-term SEO results.

3xx Status Codes Relevant to SEO

301 – Moved Permanently: The request for a resource (or URL) is permanently directed to another resource. You can set up a 301 redirect for a page that is no longer available. This directs the client to another live page rather than an error page, and it also lets search engines know they need to update their index for the page.

302 – Found: This is similar to a 301, but it is a temporary redirect rather than a permanent redirect. It directs clients from the old URL to a new one, but it does not tell search engines to update the index for the page (as a 301 would).

307 – Temporary Redirect: A 307 is more specific than a 302 redirect. The server doesn’t see the request and instead, the browser implements the redirect on its own. It is often used on websites that are served on HTTPS when they are on the HSTS preload list.

Other Important 3xx Status Codes

300 – Multiple Choices: Shows that a resource has been moved and provides a list of available alternatives.

303 – See Other: The requested resource is available on a URL that is different from the one requested.

304 – Not Modified: Client only requests the resource if it hasn’t been changed since the last document cache.

305 – Use Proxy: Access is only possible through the proxy specified in the response.

4xx Status Codes: Client Error

4xx HTTP status codes indicate that a problem has occurred on the client side. A “client” is the browser used to access a website. 4xx status errors show that there is a problem with the browser receiving information from the server.

These codes are generally undesirable for SEO because pages that are not found create a bad experience for visitors. In addition, 404 errors mean there are pages on your site that aren’t driving traffic or generating SEO results.

4xx Status Codes Relevant to SEO

404 – Not Found: The resource or URL no longer exists, and the server cannot return any information. Having 404 errors on a website can negatively impact both SEO and user experience. All 404 pages should use a 301 redirect to send requests for a nonexistent page to a live page.

410 – Gone: The resource or URL no longer exists, and it was intentionally deleted and not redirected. A 410 tells search engines that the page should be removed from the index rather than redirected to another URL.

Other Important 4xx Status Codes

400 – Bad Request: A syntax error is preventing the request from going through.

401 – Unauthorized: Authorization is required to access the requested resource.

403 – Forbidden: The user is trying to access a resource they can’t have access to.

408 – Request Timeout: The transmission timeout by the relay server from the client has expired.

410 – Gone: A resource was previously located on the URL, but it is now gone or unavailable.

429 – Too Many Requests: Client is trying to send too many requests in a short amount of time.

Other 4xx Status Codes

402 – Payment Required

405 – Method Not Allowed

406 – Not Acceptable

407 – Proxy Authentication Required

409 – Conflict

411 – Length Required

412 – Precondition Failed

413 – Request Entity Too Large

414 – Request-URL Too Long

415 – Unsupported Media-Type

416 – Requested Range Not Satisfiable

417 – Expectation Failed

422 – Unprocessable Entity

423 – Locked

424 – Failed Dependency

425 – Unordered Collection

426 – Upgrade Required

428 – Precondition Required

431 – Request Header Fields Too Large

444 – No Response

449 – Retry With (Microsoft)

450 – Blocked by Windows Parental Controls (Microsoft)

451 – Unavailable for Legal Reasons

5xx Status Codes: Server Error

5xx HTTP status codes indicate that something is wrong on the server side of things. The client made a good request, but the server is unable to complete the transfer. When a server produces 5xx errors, it can have a negative impact on SEO (as it may tell search engines to deindex a page), so it’s important to resolve these issues quickly.

5xx Status Codes Relevant to SEO

503 – Service Unavailable: There is a temporary technical issue preventing the server from processing the request. The server tells search engines that there is a deliberate halt in processing. The search engine will not change indexing status the way it would when reading other 5xx errors. If the 503 error persists for a prolonged period, search engines may start to interpret it as a permanent error and eventually de-index the page.

Other Important 5xx Status Codes

500 – Internal Server Error: An error that does not match other class errors.

501 – Not Implemented: The server doesn’t understand or cannot support the request.

502 – Bad Gateway: The server received an invalid message from the upstream server.

Other 5xx Status Codes

504 – Gateway Timeout

505 – HTTP Version Not Supported

506 – Variant Also Negotiates

507 – Insufficient Storage

509 – Bandwidth Limit Exceeded

510 – Not Extended

511 – Network Authentication Required

550 – Permission Denied

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