Complete Guide and List of HTTP Status Codes

HTTP status codes are a communication tool between servers and browsers. 

The status code is what allows both the server and the browser to know exactly what is going on when it comes to requests and responses. If you have ever noticed a “404 Error” on a website you’re trying to load, then you have seen an HTTP status code in action.

The 5 Tiers of HTTP Status Codes

There are 5 tiers of status codes, divided into a numerical system of 100s through 500s. Each tier has a general meaning, and the codes within that tier reveal more detailed, precise information about the request and response. 

• 100s: Informational Codes
• 200s: Success Codes
• 300s: Redirect Codes
• 400s: User/Client Error Codes
• 500s: Server Error Codes

Complete List of HTTP Status Codes

This is a complete list of all HTTP status codes and what they mean. We have provided additional information about the codes that you are most likely to see, which are marked with an asterisk.

Code	Category	Description
100s
100	Informational	Continue
101	Informational	Switching Protocols
102	Informational	Processing (WebDAV)
200s
200*	Success	OK
201*	Success	Created
202	Success	Accepted
203	Success	Non-Authoritative Information
204*	Success	No Content
205	Success	Reset Content
206	Success	Partial Content
207	Success	Multi-Status (WebDAV)
208	Success	Already Reported (WebDAV)
300s
300	Redirect	Multiple Choices
301*	Redirect	Moved Permanently
302	Redirect	Found
303	Redirect	See Other
304*	Redirect	Not Modified
305	Redirect	Use Proxy
306	Redirect	(Unused)
307	Redirect	Temporary Redirect
308	Redirect	Permanent Redirect (experimental)
400s
400*	User/Client Error	Bad Request
401*	User/Client Error	Unauthorized
402	User/Client Error	Payment Required
403*	User/Client Error	Forbidden
404*	User/Client Error	Not Found
405	User/Client Error	Method Not Allowed
406	User/Client Error	Not Acceptable
407	User/Client Error	Proxy Authentication Required
408	User/Client Error	Request Timeout
409	User/Client Error	Conflict
410*	User/Client Error	Gone
411	User/Client Error	Length Required
412	User/Client Error	Precondition Failed
413	User/Client Error	Request Entity Too Large
414	User/Client Error	Request–URI Too Long
415	User/Client Error	Unsupported Media Type
416	User/Client Error	Requested Range not Satisfiable
417	User/Client Error	Expectation Failed
418	User/Client Error	I’m a Teapot (RFC 2234)
420	User/Client Error	Enhance Your Calm (Twitter)
422	User/Client Error	Unprocessable Entity (WebDAV)
423	User/Client Error	Locked (WebDAV)
424	User/Client Error	Failed Dependency (WebDAV)
425	User/Client Error	Reserved for WebDAV
426	User/Client Error	Upgrade Required
428	User/Client Error	Precondition Required
429	User/Client Error	Too Many Requests
431	User/Client Error	Request Header Fields Too Large
444	User/Client Error	Precondition Required
449	User/Client Error	Retry With (Microsoft)
450	User/Client Error	Blocked by Windows Parental Controls (Microsoft)
451	User/Client Error	Unavailable for Legal Reasons
499	User/Client Error	Client Closed Request (Nginx)
500s
500*	Server Error	Internal Server Error
501	Server Error	Not Implemented
502	Server Error	Bad Gateway
503*	Server Error	Service Unavailable
504	Server Error	Gateway Turnout
505	Server Error	HTTP Version Not Supported
506	Server Error	Variant Also Negotiates (Experimental)
507	Server Error	Insufficient Storage (WebDAV)
508	Server Error	Loop Detected
509	Server Error	Bandwidth Limit Exceeded (Apache)
510	Server Error	Not Extended
511	Server Error	Network Authentication Required
598	Server Error	Network Read Timeout Error
599	Server Error	Network Connect Timeout Error

Additional Information About the Most Common Codes

Some codes are much more common than others, because the circumstances that trigger these codes occur frequently.

Code 200: OK

The 200 range of HTTP server codes communicates that it successfully completed your request. Code 200 is the general code that the server uses when a request is successful, but there is no other information to communicate. 

Code 201: Created

This is a more specific code than just communicating that the request was a success. It is used to respond to a specific creation request. For example, if the user is running a REST API to create a new user or item, the server will respond with 201 to convey that yes, it completed the creation task. Technically, a 200 code would work in this situation, too. But 201 is more precise and gives the user more information without additional work. 

Code 204: No Content

This code communicates that the request was successful, but there is no information to return following the request. The reason why this code is important is because users often expect information in response to their request. This lets them know that it’s intentional that there is no missing information. 

Code 301: Permanent Redirect

A general code in the 300s notifies the user that a website used to exist in one place, but someone moved it. The server is redirecting you to the new location.

Code 301 is used to redirect visitors (as well as bots) to a permanently changed URL. 301 is the most effective redirect code for permanent URL changes. 

Code 304: Not Modified

HTTPS Status Code 304 is used to notify the user that there have been no changes to a specific API. Most clients perform constant monitoring for changes or errors. But when they call their API for information, all they really need to know is whether or not a change has occurred. They do not need huge amounts of information to confirm this. 

Responding with a 304 is the server’s way of saying, “Nothing has changed since your last request.” 

Code 400: Bad Request

Code 400 is a general service error from the client’s side of things. It means that the request was bad or flawed. If the server knows the exact reason for the failure, it will provide a more specific response. If, however, it can’t determine the reason, the server will use Code 400. 

Code 401: Unauthorized

One kind of bad request is an unauthorized one. In this case, the server might require a log-in or an API key in order to respond. The user has failed to log in or to provide the correct API key. Code 401 is the server telling the user, “I don’t know who you are, therefore you can’t access this.”

Code 403: Forbidden

At first glance, “Unauthorized” and “Forbidden” may sound like are describing the same thing. The difference is that a 403 error is used when the API key or log-in is correct, but the user does not have the correct clearance or permissions to access the page. 

Instead of the server saying, “I don’t know who you are,” the server is now saying, “I know who you are, but you don’t have permission to be here.” A common example is when a user without administrative privileges attempts to access a page which is for admins only. In this case, the server recognizes the user. But it denies their access to the page because they do not have the appropriate permissions. 

Code 404: Not Found

This is likely the most well-known HTTP status code, as the average internet user encounters it regularly. This is the message that the server sends when you enter an incorrect URL. No page exists for that address. 

Code 410: Gone

The difference between a 404 and a 410 is that 410 means that someone removed the page. The page is no longer available, and the administrator has left no forwarding address for redirection. If you click a link and see a 410 error, the web administrator likely deleted the page without updating the links. 

Code 500: Internal Server Error

500-level codes are important because they ensure that the user knows that the error is not with them, but with the server itself. The generic 500 error informs the user that something is broken in the server or something in it, which is why they cannot access what they want to access. 

Code 503: Service Unavailable

A 503 error means that the server is unavailable to everyone trying to access it at that time. Perhaps it is undergoing maintenance or there is a temporary server overload. Regardless of reason, no one can access it and it’s best to just try again later. If a server administrator does not know why the 503 error has occurred, this should be an indication to begin troubleshooting immediately. 

Why Is It Useful to Know About HTTP Status Codes?

The average internet user can use their knowledge of HTTP status codes to understand why they are getting a specific result while they are online. 

However, they are especially useful to website administrators and developers. Knowing the meaning of each code allows you to quickly identify problems and try out appropriate solutions. HTTP status codes make the diagnostic process faster and easier.