How to Understand Those Head-Scratching API Response Status Codes
While working with APIs we should remember some of the API response’s status codes, which can help us to understand the response. Let’s deep dive of all the status codes.
Table of Contents
Introduction
An Application Programming Interface (API) is a set of instructions, protocols, and tools used to create software applications. An API acts as an interface between two different applications enabling them to communicate with each other. In simple terms, it is like a waiter in a restaurant who gets the order from customers and serves it back to them after preparing them in the kitchen.
Response status codes are HTTP status codes that indicate the success or failure of an API request. These are sent by the server when responding to requests, allowing clients to understand what happened with their requests and take appropriate action accordingly.
The most common response status codes are 200 (OK), 404 (Not Found) and 500 (Internal Server Error).
Each one indicates a specific type of response based on whether the request was successful or not and more detailed information about why it may have failed if necessary.
Must Read: Essential Tips For Navigating the API Testing Journey
Overview of Response Status Codes
1xx
1xx Informational responses are usually used for early communication between the server and the client. It is typically used to indicate that the request was received successfully, but further action must be taken by the user agent in order to fulfill the request. Examples include 100 (Continue), 101 (Switching Protocols) and 102 (Processing).
2xx
2xx Success status codes indicate that a client’s request has been successfully fulfilled by a web server. Some examples of this type of response include 200 (OK), 201 (Created), 202 (Accepted), and 204 No Content).
3xx
3xx Redirection messages are sent when there is an issue with how a URL is structured or if content needs to be served from another location due to temporary issues at its original address. Common 3xx responses include 301 Moved Permanently, 302 Found, and 304 Not Modified.
4xx
4xx Client Error status codes indicate that there was an issue with what was submitted in the request made by the client which prevented it from being processed correctly by the web server. Common 4xx errors include 400 Bad Requests, 401 Unauthorized and 404 Not Found.
5xx
5xx Server Error status codes indicate that something went wrong on our end while trying to process your request due to either programming bugs or system malfunctions on our side of things. Popular 5XX errors you might come across are 500 Internal Server Error, 502 Bad Gateway and 503 Service Unavailable error messages respectively.
Informational Codes
The 100 Continue response code is sent from a server to a client in order to indicate that the initial part of the request has been received and that the client should continue sending the remainder of its request body. This allows for an efficient way for clients to send large amounts of data without having to wait for a full response before proceeding.
The 101 Switching Protocols status code indicates that the server is willing to switch protocols, as requested by the client, in order to complete a request successfully. This can be used when making requests which require different protocol versions or technologies such as WebSockets. Clients can then use the information provided by this code when deciding how best to proceed with their requests.
Successful Codes
The 200 OK response code is the most common success status and indicates that a request was successfully received, understood, and accepted. This means that the server has fulfilled all requirements for a successful response and can be used when sending back requested information or data from an API endpoint.
The 201 Created response code indicates that the request made by a client resulted in the server creating a new resource. This could mean anything from creating a new user account on an application to saving new data in a database. It provides confirmation that something was created as requested by the client.
The 202 Accepted status code informs clients of their requests being accepted but not yet processed by the server which can take time depending on what action needs to be done after accepting it. The accepted message is usually sent immediately with more detailed responses following up once everything has been completed successfully or failed due to some issue within processing it.
The 203 Non-Authoritative Information status code indicates that while valid content was returned in response to your request, it may have originated from another source other than what you were expecting such as cached content instead of live data from an API endpoint or website page, etc.
Finally, 204 No Content sends out no-body content along with its header indicating resources are available but nothing else should be expected back in terms of results like images, videos or text documents etc.
Redirection Codes
The 300 Multiple Choices response code is used to inform a client that there are multiple options for the resource requested and the user must choose one of them. This is often seen when websites have different versions of pages based on geographical location or browser type etc. It will provide a list of possible resource locations so the user can select one which best suits their needs.
The 301 Moved Permanently status code indicates that the URL requested by a client has been permanently moved to another address and should be updated with this new information in order to continue making requests successfully. This could mean changing links, bookmarks or other references so they point towards the correct location instead of an outdated version that no longer exists anymore.
The 302 Found response code informs clients that although their request was successful, it has been temporarily redirected to another address due to technical issues at its original destination such as maintenance periods etc. Once these issues have been resolved, then clients must update their references accordingly in order for future requests not to redirect again needlessly like before.
The 303 See Other message is sent when a request made by a client requires further action from them upon receiving its results such as submitting more detailed forms or providing additional credentials in order for access rights etc. This will usually contain instructions on how users can complete these extra tasks if needed and provides useful guidance throughout complex processes like authentication procedures etc.
Finally, 304 Not Modified status codes indicate that while valid content was returned in response to your request, it may have originated from another source other than what you were expecting such as cached content instead of live data from an API endpoint or website page etc. In cases where nothing has changed since the last time the same URL was requested (i.e., no updates) then this code would be sent back telling clients there’s nothing new here move along now!
Client Error Codes
The 400 Bad Request response code is sent from a server when the request received by it does not meet certain criteria or is invalid due to incorrect syntax. This could be caused by submitting an incomplete or incorrect form, sending the wrong parameters in an API request etc. It basically tells clients that something isn’t quite right and needs to be fixed before continuing, otherwise their requests will remain unsuccessful.
The 401 Unauthorized status code informs clients that their requests can only be fulfilled if they provide valid authentication details such as username and password combinations for example. Unless these credentials are supplied then the server won’t allow access to whatever resource has been requested which makes this response ideal for protecting sensitive information on web servers like bank accounts etc.
The 402 Payment Required message lets users know that payment must first be made before accessing the resource being requested by them. This often occurs with premium services or products where credit cards are used as a form of secured payment before allowing access rights afterward depending on the success/failure of transaction processing etc..
Additionally, 403 Forbidden status codes indicate that while valid content was returned in response to your request, it may have originated from another source other than what you were expecting such as cached content instead of live data from an API endpoint or website page etc. In cases where nothing has changed since the last time the same URL was requested (i.e., no updates) then this code would be sent back telling clients there’s nothing new here move along now!
Finally, 404 Not Found error messages let users know that whatever they were looking for couldn’t be found at its specified address which could mean either a typo in the URL entered into their browser window or perhaps even deleted pages due to changes within websites over time without updating existing links accordingly etc.. By returning this particular error message users can quickly identify potential issues needing resolution so they can find what they’re looking for eventually without much hassle involved usually.
Server Error Codes
The 500 Internal Server Error response code is sent when a server encounters an unexpected condition that prevents it from fulfilling the request made by a client. This can be caused by software or hardware-related issues, corrupt data files, invalid configurations etc. It basically means something went wrong on the server side and needs to be resolved before further requests can be successfully completed again.
The 501 Not Implemented status code informs clients that their requested action cannot currently be fulfilled due to its complexity or lack of availability within system resources at present time. For instance, a website may not have implemented support for incoming API calls yet which will result in this error message being returned instead until updated accordingly afterward if needed.
The 502 Bad Gateway message lets users know that while valid content was returned in response to your request, it may have originated from another source other than what you were expecting such as cached content instead of live data from an API endpoint or website page etc. In cases where nothing has changed since the last time the same URL was requested (i.e., no updates) then this code would be sent back telling clients there’s nothing new here move along now!
Additionally, 503 Service Unavailable error messages let users know that whatever they were looking for couldn’t be found at its specified address which could mean either a typo in the URL entered into their browser window or perhaps even deleted pages due to changes within websites over time without updating existing links accordingly etc. By returning this particular error message users can quickly identify potential issues needing resolution so they can find what they’re looking for eventually without much hassle involved usually.
Finally, 504 Gateway Timeout codes indicate that while valid content was returned in response to your request, it took too long for the server to respond and thus failed after exceeding certain thresholds set beforehand like maximum execution times per request etc. This should help prevent servers from getting overloaded with too many requests simultaneously allowing them some breathing room during peak hours when traffic suddenly spikes up
Conclusion
Response status codes are essential for providing an efficient and reliable web experience since they inform clients of the success/failure of their requests in a meaningful way.
By using them, developers can quickly debug issues with applications or websites without having to manually inspect each response individually which saves valuable time in the long run. Additionally, these codes enable users to know exactly when something has gone wrong so that they can take corrective measures immediately if needed instead of waiting around aimlessly for a response from the server side.
Furthermore, by implementing proper error handling techniques such as returning informative messages that contain useful information about what went wrong (e.g., 401 Unauthorized) then users are less likely to become frustrated due to not understanding why their request failed in the first place and may even be able to fix it themselves before needing further assistance from technical support teams etc.
Therefore, being aware of the different types of response status codes available is key for creating robust applications that provide great user experiences at all times regardless of whether or not everything goes according to plan on occasion or not.
