HTTP Status Codes


When users request data from web applications and API APIs (application programming interfaces) are a set of protocols and definitions developers use to build and integrate application software. APIs act as the connective tissue between products and services. (application programming interface) services, those service's servers issue HTTP status codes in response. Creators Also known as Unqork Users, or Designer Users; is anyone who is inside the Unqork platform. can use these response codes to analyze if calls to web apps and APIs are successful or erroneous to adjust their requests as needed. Sometimes, end-users End-users, also known as Express Users, are the individuals accessing an application through Express View. In most cases, end-users are the customers using the product. might see these status codes when sending a request to the server. For example, an end-user might see the status code 404 in their browser if the web page they are trying to reach is unavailable.

HTTP Response Status Code Categories

HTTP response status codes break down into five category ranges:

  • 100-199: Informational Responses informing the client their request was received, and the process continues.

  • 200-299: Successful Responses informing the client their request was successfully received, understood, and accepted by the server.

  • 300-399: Redirection Responses informing the client that additional action needs to be taken to complete the client request.

  • 400-499: Client Error Responses indicating an error occurred in the client's request, or the request cannot be fulfilled.

  • 500-599: Server Error Responses indicating the server could not process a request that might be valid.

Below are the most common response codes by category.

Information Response Codes

This class of status codes indicates a provisional response provided by the server. Response codes in the 1xx range inform the client that everything is OK and the request should continue to progress.

Status Code

Name Description



This code indicates a client should continue the request or ignore the server response if their request has already completed.


Switching Protocols

This code is sent in response to an Upgrade request header from the client. It indicates the server switching protocols.


Early Hints

This code is used with a Link header, enabling the user to start preloading resources while the server prepares a response.

Successful Response Codes

Status codes in this range indicate a successful response. The type of success depends on the client's request.

Status Code

Name Description



The client's HTTP request succeeded.



Typically sent after POST requests and some PUT requests.



The client request is received but the server has not acted upon it. This response is intended for batch-processing, or where another process handles the request.


Non-Authoritative Information

The returned metadata is not the same as what is available from the server. Typically used for mirrors or backups of other resources.


No Content

There is no content contained in the response, but the headers might contain useful information.


Reset Content

Instructs the user agent to resend the document that sent this request.


Partial Content

Typically used when a Range header is sent from the client for requesting only part of a resource.

Redirection Response Codes

The 3xx range of status codes indicate that a request has more than one possible response. The client might need to choose a response to continue their request.

Status Code

Name Description


Multiple Choice

This response is used when the client request has more than one choice.


Moved Permanently

The URL of the requested resource has moved permanently. The new URL is delivered in the response.



The URI of the requested resource has changed temporarily, and further changes might happen in the future.


See Other

This response directs the user agent to GET the requested resource at another URI.


Not Modified

Used for caching purposes. Informs the client the response is not modified. The client can use the previously cached version of the response.


Temporary Redirect

This response is sent when the server directs the client to GET the requested resource at another URI.


Permanent Redirect

The resource has permanently relocated to another URI specified by the Location response header. This is similar to the "301 - Moved Permanently" response, but it instructs the user not to change the HTTP method if a POST is used in the first request.

Client Error Response Codes

Status codes in the 4xx range indicate an error in the client's request. User agents should display these codes to the end-user when they occur.

Status Code Name Description


Bad Request

This response occurs when the server cannot or will not process the request due to user error.



The user is unauthenticated and must authenticate to get the requested response.



The requester does not have access to the content. The server refuses to deliver the requested resource.


Not Found

The server cannot find the requested resource.

  • In a browser: The URL is not recognized.

  • In an API: The endpoint might be valid, but the requested resource does not exist.


Method Not Allowed

The target resource does not support the request method.


Not Acceptable

This response occurs after server-driven content negotiation fails to find content that conforms to the request issued by the user.


Proxy Authentication Required

Authentication needs to be completed by a proxy.


Request Timeout

Servers send this response to close out idle or unused connections.



There is a request conflict with the current state of the target resource. Conflicts occur more often with PUT requests.



Access to the target resource is no longer available.


Length Required

The server rejected the client request because the Content-Length header field is not defined, and the server requires it.


Precondition Failed

The request has preconditions in its headers that the server does not meet.


Payload Too Large

The requested entity is larger than the limits defined by the server. The server might return a Retry-After header or close the connection.


URI Too Long

The URI request by the client is longer than the server is willing to process.


Unsupported Media Type

The server does not support the media format of the requested data.


Range Not Satisfiable

The range specified in the Range header request cannot be fulfilled.


Expectation Failed

The server cannot meet the expectation set by the Expect request header field.


Upgrade Required

The server refuses the request using the current protocol, but might accept it after the client upgrades to a different protocol.


Precondition Required

The server of origin requires the request to be conditional. This is intended to prevent lost updates.


Too Many Requests

The user has sent too many requests in a given period of time.


Request Header Fields Too Large

The server refused the request because its header fields were too large.


Unavailable For Legal Reasons

The request cannot be legally provided. This error might occur when a government censors a web page.

Server Error Responses

Status codes in the 5xx range indicate cases where the server is aware that it has erred, or is unable to perform the request. User agents should display these codes to the end-user when they occur.

Status Code

Name Description


Internal Service Error

This server has encountered an issue it is unable to handle.


Not Implemented

The server does not support the client request method. The only required methods that servers support are GET and HEAD.


Bad Gateway

While working as a gateway, the server receives an invalid response.


Service Unavailable

The server is not prepared to handle the request. This might occur if the server is down for repairs or overloaded.


Gateway Timeout

While working as a gateway, the server cannot get a response in time.


HTTP Version Not Supported

The Server does not support the HTTP version used in the request.


Variant Also Negotiates

The server has an internal configuration error: the chosen variant resource has been configured to engage in transparent negotiation itself instead of an end point.


Not Extended

Further extensions to the request are required for the server to fulfill it.


Network Authentication Required

The client needs to authenticate to gain network access.