When you visit a web page, your computer’s web browser communicates with the web server of the website. Your web browser, also known as the client, submits a request to the web server for web page to be delivered. The web server always returns a reply in the form of response code or status codes.

The server uses HTTP codes and redirects to let you know how your request to access a specific webpage went. HTTP codes and redirects can make a big impact when troubleshooting website configuration errors. They are also helpful for marketers to boost SEO efforts as well.

The first digit (from left) os the status code indicates its general meaning.

1xx: Informational

This class of status code indicates a provisional response. Any HTTP codes and redirects in the 100s is a message from the server that your browser request is still processing and ongoing.

2xx: Success

You should send the client to a web page with this response code. They let you know that your request was received and processed by the server without issue.

3xx: Redirection

These response codes help update the client’s outdated request. These redirect codes are sent by the server to indicate that a new resource was submitted, replacing the webpage initially requested.

4xx: Client Error

The request went wrong and the error is by the client. The most frequent response of this type is a broken link when the client requests web page not existing on the server. Status codes in the 400s are important to recognize, since these are problematic. They let you know there is an issue with your request to access a webpage.

5xx: Server Error

The request went wrong and the error is by the server. They appear when your request to view a webpage was successful, but there is an issue in the server.

Status Codes

200 - OK

A 200 response from the server means that everything is fine and the server sends the requested information to the client. This response code is generally ideal.

301 - Redirect Permanently

A permanent redirect means that the web page has been shifted to new address permanently. Instead of showing old information, the server begins an updated request. A 301 response leads to a 200 response from the new location.

When search engine sees 301 code, old URL is replaced by the new one in a search index. No ranking is lost in this manner.

302 - Found or Temporary Redirect

Temporary redirect means that the web page is at different URL temporarily. The server begins a new request, resulting in a 200 response from the new location.

When search engine sees 302 code, the originally requested location is retained in a search index. This is the main difference from 301 response code.

304 - Not Modified

The 304 status code redirects to a file previously cached by the client. It means that the web page or information has not changed since the last time client asked for it.

403 - Forbidden

A 403 response means that the client does not have the authority or the access level for the requested information. When an unauthorized client is attempting to access sensitive areas of a website, a 403 code is shown.

This status is also sent to the search engines who try to crawl administration pages of a website.

404 - Not Found

A 404 response means that the URL does not exist. It is the most widely-recognized status code. Whenever you visit a URL that does not exist, a 404 error is displayed.

The 404 response is not an error with the server, but the result of outdated or wrongly-typed links. You should fix 404 results from internal site links.

410 - Gone

This status code means that the URL existed before, but now it has been gone and no more exists. It tells search engine crawlers and other websites that the requested information was available only for a limited time, and they should remove their links to it.

503 - Service Unavailable

The 503 status code is generally used when the server is overloaded and unable to respond to requests. The reason for this overload can be server configuration, or a sudden increase in website traffic.