HTTP Status Codes are a crucial part of web development and any engineer who does API integrations should have a good handle on at least the most common of the codes.

Let’s take a deeper dive into the 5xx status codes and understand what the codes mean and what behaviors you can expect from the server when you receive one of these codes from an API endpoint.

What do the 5xx status codes mean?

The 5xx status codes indicate server-side errors, something that the server itself cannot respond to – this could be an application error or an internal server problem. In an ideal world, these would never be seen as these problems are usually ones that the server team can take action on, so if you see these occurring in your API traffic, it’s definitely worth getting in touch with the server team to investigate the trouble!

The most common 5xx codes are 500 (Internal Server errors), 502 (Bad Gateway), 503 (Service Unavailable), and 504 (Gateway Timeout). Let’s look at each of these codes in further detail.

Ready to gain an understanding of 5xx status codes? Let’s dive in and explore this world of HTTP responses!

Quick Review of Key Points

5xx status codes refer to the range of HTTP status codes indicating server errors. Examples of common 5xx status codes include 500 Internal Server Error, 501 Not Implemented, and 503 Service Unavailable.

What are 5xx Status Codes?

5xx status codes are a category of HTTP error responses that indicate a server-side issue. In order to understand 5xx codes, it is necessary to know what an HTTP error response is in general. HTTP error responses are defined as a standard response used by web servers/applications to indicate that there was an issue with the user’s request. When a user lands on a webpage, the server sends out a response code notifying the browser of whether or not their request for the page was successfully fulfilled. A successful response code will be in the 2xx range and an unsuccessful one will be in the 4xx or 5xx.

As mentioned earlier, 5xx represents errors caused by the website server itself and it cannot be fixed by the user. Such codes let you know that something is wrong on the website’s side, and it’s due to misconfiguration or some other server-side problem which needs to be resolved by the site administrator. Some experts argue that users should not be presented with any form of 5xx error since they indicate issues beyond a user’s control and could damage their reputation or even put off potential customers. On the contrary, others suggest that such errors give users confidence in the commitment of site administrators to keep their platform up-to-date as problems can get noted and quickly rectified if detected early enough.

To recapitulate, 5xx status codes are a type of HTTP error responses indicating server side issues which may impact users but could also reflect well on website maintenance if promptly corrected. In the following section, we will explore some of the common types of 5xx errors.

Key Points to Know

5xx status codes are HTTP error responses signaling errors caused by website server issues that cannot be fixed by users. While some suggest that such errors should not be presented, others argue they demonstrate a website administrator’s commitment to platform maintenance. 5xx errors can provide an opportunity for quick rectification if detected early enough. Common types of 5xx errors will be explored in the following section.

What are the Types of 5xx Codes?

The 5xx series of status codes indicates there has been a server-side error. The server is aware that it has encountered an error or is unable to process a particular request, and the client receives this information in the form of a 5xx status code. Network requests that result in a 5xx response are not successful and must be retried by the client. These types of errors can arise from mistaken configurations, hardware or software issues, or unforeseen circumstances like high load on the server.

There are seven primary types of 5xx status codes: 500 Internal Server Error (most common), 501 Not Implemented, 502 Bad Gateway, 503 Service Unavailable, 504 Gateway Timeout, 505 HTTP Version Not Supported, and 506 Variant Also Negotiates.

The 500 Internal Server Error is the catch-all for any situations where the server encounters an unexpected condition that prevents it from fulfilling the request. This can happen when a server is misconfigured or experiences an unexpected event such as resource exhaustion or down hardware. It’s also returned when certain servers encounter malformed requests which lead to unpredictable results. For example, if a server is expecting POST data with vital attributes for completing the request, but these attributes are missing or invalidated, it will return an Internal Server Error. While most 500 errors are generally safe and pose no security risks to sites and applications, servers should be properly configured to minimize their occurrence and properly handle requests that produce them.

The 501 Not Implemented status code informs clients that the requested functionality was not available on the server. This can happen when incompatible versions between client and server are present or when the server does not support features requested by legacy clients using outdated protocol versions.

The 502 Bad Gateway status code is sent when the client’s request reaches a proxy or gateway which itself received an invalid response from another source downstream of its own network path. This type of error can often be caused by misconfigurations like faulty firewall rules or outages experienced at lower layer networks like ISPs.

Status code 503 Service Unavailable occurs when proper communication with a web service fails due to unavailability of one component either due to maintenance or overloading; this informs clients that normal activities should resume once necessary maintenance operations have completed and resources become available again. A number of retry attempts can be made until service resumes normal operations though it’s important to ensure throttling mechanisms are implemented to prevent sprawling numbers from flooding servers leading to yet another overload situation in cascade cycles.

The 504 Gateway Timeout status code returns when gateway servers waiting too long for responses from other services timeout in their attempts to fulfill certain requests. Load balancers and reverse proxies sometimes serve as gateways for applications making them subject to 504 errors if upstream online databases experience long delays in responding then causing downstream servers serving applications waiting on response data exceeding their allotted allowed wait time periods before timing out in conclusion triggering the 504 responses intended for sending back upstream signifying timeouts in network communications exchanges occurred within scheduled duration settings established previously..

The 505 HTTP Version Not Supported status code appears when a newer version of HTTP than supported by the server is used while trying to complete a transaction over network communications protocal connections returning messages back indicating that none acceptions being supported at time of request transmission transmissions initiated by origins located elsewhere..

Finally, 506 Variant also Negotiates occurs when two conflicting variants exist during content negotiations between clients and web servers after requests have been exchanged over networks connections effectively resulting in deadlock situations where neither variants nor previous negotiation states nor ensuing replication attempts yield acceptable outcomes leading up dead ends established uncontainable conditions triggering the returns of 506 Variant also Negotiates statuses back indicating unsuccessful completions were found because those involved failed to move forward successfully with respective transactions executed thereby instead concluding hastily accordingly soon thereafter ableily fulfilling expected deliverables intentions initialed previously leaving everybody walking away empty handedly yet wiser thus better prepared for any scenarios similar arising anytime later than within mentioned lengths respectively durations given .

Now let’s dive into understanding how these 5xx errors differ from 4xxx series codes in our next section…

  • A 5xx status code indicates that the server is aware that it has encountered an error or is otherwise incapable of performing the request.
  • The most commonly seen 5xx status code is the 500 Internal Server Error, which occurs when the server is unable to complete a request due to a server issue.
  • According to, 4xx status codes indicate a client error and 5xx status codes indicate a server error.

How the 5xx Series Differs from the 4xx Series

The 5xx series of HTTP error responses differs from the 4xx series in that the issues causing a 5xx error are not related to the client-side request. If a client sends a request to the server and receives a 5xx status code, this means that something is wrong on the server-side and needs to be fixed by the host. In fact, all 5xx status codes indicate that the server was unable to fulfill an apparently valid request. It is important to note that there are various types of 5xx errors, so it is important for developers to understand each one and how they work in order to respond appropriately.

Another key difference between 4xx and 5xx series errors is that 4xx errors can be handled by modifying certain aspects of the request or configuration from the client side. On the other hand, most 5xx errors should be addressed directly by the server or hosting provider in order to resolve them completely. This is because many times when a server generates a 5xx response it indicates something more serious than just an invalid request. It may be indicative of a bug or underlying issue within the application itself or failure within the hosting environment such as inadequate resources being available or even general server downtime.

In either case, understanding each of the individual http status codes within the range 5XX–which will be discussed in greater detail in the following section–is essential in order to properly address these types of errors as they occur. Therefore, it is essential for developers to have an understanding of both 4xx and 5XX status codes in order to quickly recognize which type of error applies in any situation, thus allowing them to accurately troubleshoot and remedy requests as quickly as possible.

Now let’s take a closer look at some of the most common 5XX error response codes: 500, 502, 503 and 504 status codes.

A Closer Look at 500, 502, 503 and 504 Status Codes

When it comes to understanding 5xx status codes, 500, 502, 503 and 504 are some of the most common and widely used. These four are all server error responses and indicate that something has gone wrong when trying to connect to a web service.

When a 500 status code is returned, it generally indicates an internal server error. This means that the server you’re trying to communicate with experienced an unexpected condition, preventing it from fulfilling your request. The underlying cause can be anything from an overloaded process or a failed database system due to incorrect configuration or unexpected data values. Generally, fixing 500 errors requires troubleshooting by a qualified administrator, who must fix the underlying problem before the resource can be accessed again.

The 502 status code indicates that a gateway received an invalid response from an upstream server while attempting to fulfill the request. This can be caused by misconfigured caching software or faulty middleware components attempting to contact other services for additional information required to respond to the request. In order to serve users with this request successfully, the issue must be resolved by addressing any underlying problems with the upstream servers or third-party services involved in responding to requests.

503 status codes indicate that a service or endpoint you’re trying to access is temporarily unavailable as it is being serviced or maintained. When such errors occur, typically the resource being requested will become available again quite quickly after whatever maintenance is being done is completed. However, this error should not be ignored as if 503 errors become persistent, then there may be larger issues with availability of the back-end services involved in processing requests which need attention.

And finally, mistakes in DNS configuration on either the client side or server side often result in generating 504 status codes in browsers when requesting a web page. If this issue occurs consistently despite retries it may mean that there’s an issue either with your own computer’s DNS setup or even an issue with your ISP’s DNS servers – both could be causing requests for resources to be redirected incorrectly causing these sorts of errors when browsing online pages and services.

Other 5xx Status Codes are still available and should not be overlooked when dealing with 5xx status codes; they provide useful insights into server performance and user experience when dealing with HTTP requests and responses from web services. Understanding their purpose and potential causes helps us both keep our websites running smoothly and quickly address issues when they do arise so that websites continue to remain accessible for our users at all times.

Other 5xx Status Codes

When it comes to 5xx status codes, there are several widely recognized codes within the range, including 500Internal Server Error, 502 Bad Gateway, 503 Service Unavailable and 504 Gateway Timeout. But did you know that other lesser-known 5xx codes exist? These additional 5xx codes—while not as common—are still important to be aware of when diagnosing errors.

Starting with 505 HTTP Version Not Supported, this code is used when the server does not support the HTTP version requested by the client. Typically this means that the client is using an outdated or unsupported version of HTTP. This error can usually be corrected by upgrading the HTTP version being used.

Next is 506 Variant Also Negotiates (VAR), which is triggered when a request has a circular reference in information between two versions and a browser cannot negotiate between them. It’s recommended that developers review their configuration and remove the circular reference loop if possible so that VAR can be avoided.

Then there is 507 Insufficient Storage, which occurs when a server will not store any more resources due to lack of space or full storage capacity. To remedy this issue, developers may need to explore alternate data stores if possible or increase existing storage capacity.

And lastly, there’s 511 Network Authentication Required, which indicates that clients attempting to access certain resources must authenticate in order to gain access. In this case developers should ensure end users are provided with a proper authentication process for resources security.

Now that we’ve covered quite a few of the lesser-known yet essential 5xx status codes beyond the more popular ones, let’s move on to discussing other applicable ones like 505, 506, 507 and 511 status codes in the next section.

505, 506, 507 and 511 Status Codes

505 and 506 Status Codes

The 505 and 506 status codes indicate that the requested resource could not be served by the server due to an internal server error. The variance between the two codes is that a 505 code indicates that the request was improperly formatted whereas a 506 code implies the requested resource could not be met due to an internal server issue. In both cases, the web server may simply need to be restarted or re-configured in order to fix the issue.

507 and 511 Status Codes

A 507 code occurs when a server is unable to store the requested resource due to insufficient storage space. In most cases, this error can be resolved if additional storage resources are allocated or if existing files on the server are removed in order to free up more space for new ones. On the other hand, a 511 status code usually results from a client unsuccessfully providing valid credentials when attempting to access a restricted resource. The only way to restore functionality in this case is for the client to enter valid credentials or re-request authorization.

Final Thoughts on 5xx Status Codes

It’s important for developers, sysadmins, and users alike to understand what 5xx status codes indicate and how they should be resolved in order to restore full functionality of any given website. Ensuring that web servers are configured properly, have sufficient storage capacity and that user credentials meet authentication requirements are all key components of keeping website operations running smoothly. By taking these steps into account before any issues arise, developers and system administrators can ensure HTTP error responses are limited as much as possible.

Final Thoughts on 5xx Status Codes

When dealing with HTTP status codes, it’s important to understand the different types of errors and why they occur. In particular, 5xx status codes are traditionally seen as server-side errors and identify the server’s inability to handle a user request. It is possible for server errors to be caused by a variety of issues from whether applications have crashed or failed unexpectedly to overloaded databases.

While 5xx status codes are often associated with bad user experiences since they signal an issue within the system, they are also necessary in ensuring that web servers and applications communicate properly. On one hand, these codes can help web owners monitor their services so they can quickly identify potential problems and fix them right away. On the other hand, 5xx status codes provide users with information about why something has gone wrong and signs that help them understand when and why the server experienced an error.

Finally, if you find yourself in a situation where your website or application is displaying a 5xx status code, it is important to take the necessary steps to investigate what caused this issue before it causes further disruption. This can include running debugging tests or restarting services as well as updating software packages when available. When it comes to debugging services, it is essential to use tools such as logs and events that can provide meaningful information about the error condition or code being received. However, note that even if you have identified the problem correctly clients may still face an outage due to prolonged recovery time which can take hours or days depending on the nature of problem.

Overall, 5xx error responses are powerful diagnostic tools that provide valuable information about when something within the server has gone wrong. Nevertheless, these errors should be monitored closely as they may spell out serious issues that need to be addressed promptly in order to ensure a good user experience.

Common Questions

Questions I would ask about “5xx status codes”:

  1. What causes 5xx status codes to be returned?

    Answer: 5xx status codes indicate a server error, meaning that the server encountered an unexpected condition that prevented it from fulfilling the request. Common causes of this type of issue include invalid requests, a lack of available resources (such as memory or disk space), misconfigurations, issues with third-party API’s, and problems with coding syntax.

    2. How can I identify and troubleshoot 5xx errors?

    Answer: Identifying a 5xx error requires checking the server’s response and associated logs. This can be done either manually or by using automated tools like a logging service or monitoring software. Once identified, troubleshooting 5xx errors should begin with ruling out potential root causes such as incorrect configurations and coding errors. If these attempts do not resolve the issue, deeper investigation may need to be done with tracing requests and examining performance metrics to determine what is causing the server error.

What are 5xx status codes?

A 5xx status code, also referred to as a server error, is a class of HTTP responses indicating the server is aware that something went wrong while trying to fulfill the request. The 5xx class of status codes includes 500 Internal Server Error, 501 Not Implemented, 502 Bad Gateway, 503 Service Unavailable, 504 Gateway Timeout, and 505 HTTP Version Not Supported.

The main cause of 5xx errors is server-side problems, specifically from server overload or programming bugs. When a web browser receives a 5xx error message from the server when trying to access an online resource, it means the server cannot process the request for an unknown reason.

Generally, a proper fix for these types of errors involves troubleshooting and increasing the server’s resources if necessary (for example RAM or disk space). It can also involve debugging any programming conflicts or software bug issues. Depending on the specific issues involved in each particular case though, some 5xx errors may require more extensive modifications to rectify them permanently.

How do 5xx status codes impact SEO?

5xx status codes are server-side errors that indicate a problem with web page requests. As such, they can have a significant impact on search engine optimization (SEO). When search engine robots crawl a website, they look for status codes that give signals about the website’s health and content. If 5xx codes are present, this can signal to the robot that the page is incomplete or unreliable and thus should not be indexed by search engines. In addition, because these errors typically occur when an unexpected issue occurs during server communication, it could result in the robots crawling the website more often than normal—a situation which could also influence SEO rankings negatively.

As such, it’s important to address any 5xx status codes as quickly as possible in order to ensure optimal SEO performance. This can include reconfiguring server settings or troubleshooting code issues that might be causing the error. Fixing these issues may also speed up page loading times and improve user experience, both of which are further factors in determining SEO success.

What is the purpose of a 5xx status code?

The purpose of a 5xx status code is to indicate server-side errors when an HTTP request cannot be fulfilled. A 5xx error can occur for various reasons, including resource exhaustion, misconfiguration, or overloaded servers. In most cases, a 5xx status code will indicate that there is something wrong with the server itself, and not the client’s request. For example, a 500 Internal Server Error might indicate a bug in the code, whereas a 504 Gateway Timeout would mean that the server was unable to complete the requested action in time. Ultimately, all 5xx status codes are indicative of issues on the server-side and should be addressed as soon as possible.

What are the different types of 5xx status codes?

5xx status codes refer to a range of server errors and indicate that the server was unable to fulfill an apparently valid request. 5xx status codes are subdivided into five categories, 500, 501, 502, 503, and 504.

A 500 Internal Server Error is the most commonly encountered 5xx error code. This indicates that something unexpected has happened on the server that prevented it from fulfilling the request. Normally this could be due to a bug in a script or an incorrect file/folder permission on the server.

A 501 Not Implemented error indicates that the server doesn’t recognize or support the request method given by the client. This usually happens when requesting a resource with a method not supported by the server (e.g., using PUT instead of POST).

A 502 Bad Gateway occurs when a proxy or gateway receives an invalid response from another server. This generally indicates that an upstream server is either offline or refusing requests.

A 503 Service Unavailable means the server is temporarily unavailable for maintenance or other reasons. The user can try again at a later time.

Finally, a 504 Gateway Timeout means that a gateway or proxy hasn’t received a timely response from another server. It is possible that the issue is related to networking or connectivity problems between servers on different networks.

In conclusion, there are five distinct types of 5xx status codes: 500 Internal Server Error, 501 Not Implemented, 502 Bad Gateway, 503 Service Unavailable, and 504 Gateway Timeout. Each represent a different type of error and should be handled accordingly when troubleshooting issues with your web application or website.

Last Updated on March 21, 2023

Matt Jackson

E-commerce SEO expert, with over 10 years of full-time experience analyzing and fixing online shopping websites. Hands-on experience with Shopify, WordPress, Opencart, Magento, and other CMS.
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