Observability
HTTP Probe error codes
This article provides a list of common error codes in the HTTP Probe tool and steps to resolve them.
First published date
11/1/2023 1:51 PM
Last published date
10/30/2025 9:01 PM
Overview
This article provides a list of common error codes in the HTTP Probe tool and steps to resolve them.
Product section
Hybrid Cloud Observability
Resolution
While working with HTTP(s) Probe tool, multiple errors may arise. Review the following common error codes and their possible resolutions.
When "Ignore CA, CRL, and CN Errors" is unchecked, the probe output might return a certificate error. This usually means that the trust connection between the probe and the server cannot be established, and the site cannot be trusted.
Client Errors (4xx)
These refer to the errors caused due to client-side errors, for example, malformed request syntax, invalid request, invalid request message framing, or deceptive request routing.| Error Code | Name | Explanation | Resolution |
|---|---|---|---|
| 400 | Bad Request Error (400) | This is one of the most common types of 400 errors, because it has a lot of potential causes. Essentially, the 400 Bad Request error will pop up when your web server can’t process a request body due to some mistake on the client’s end. This can happen because of an invalid URL, malformed syntax, and other reasons. | Since there are so many potential causes for a bad request error, there are a lot of fixes for it. For example, one can check for misspellings in the URL typed, clear the cookies, or empty the cache. If none of these methods work, the error will often clear up on its own on retry the probe after some time. |
| 401 | Unauthorized (401) | This error will only appear when the client isn’t authorized to access the URL being probed. | Checking and correcting the credentials provided for authentication may fix this error. |
| 403 | Forbidden (403) | This error tells us that the server is refusing our requested resource for one reason or another, and the underlying cause is at our end. For example, if authentication is needed to access a specific URL, the server might respond with a 403 Forbidden error code. | In any case, there’s usually a good reason you can’t access the resource you want. So this is a type of error you might not be able to circumvent. |
| 404 | Not Found (404) | This error means that the client was able to establish a connection to the site’s server, but couldn’t find what it was looking for. In other words, this is the error which occurs when a client tries to access a resource that doesn’t exist. | This usually happens because the URL was mistyped, the page changed its address, or the website you’re trying to visit isn’t there anymore. |
| 405 | Method Not Allowed (405) | This error occurs when the client connects to a server, but the request can’t be completed because you’re using the incorrect HTTP method. | |
| 406 | Not Acceptable (406) | Error 406 occurs when the client requests a response using an Accept header, and the server at the other end can’t fulfil it. When the client makes an Accept request, it specifies what type of character set, language, or file type it needs. If the server can’t provide a response body that ‘matches’ that request, one is likely to see the 406 Not Acceptable error. | |
| 407 | Proxy Authentication Required (407) | This error shows up when the client tries to connect to a server, but the client can’t complete the process because it lacks authentication from a proxy that’s acting as a middleman. | |
| 408 | Request Timeout (408) | When trying to access a resource, the client connects with the server and requests that it send the information needed to display that site. However, sometimes the client won’t make the necessary requests within a reasonable timeframe. That often results in the 408 Request Timeout error. | The best strategy to get rid of this error is to retry probe. The 408 Request Timeout will usually go away on its own, unless the internet connection is experiencing problems. |
| 413 | Payload Too Large (413) | When the client makes a request to the server, it receives data in return. However, there’s a limit to the amount of data that any given server can process at one time. If this error is seen, it means the server can’t or won’t process the request, because it involves too much information. | The request itself will need to be simplified if it’s going to work properly. |
| 429 | Too Many Requests (429) | This error will be returned if there are an excessive number of requests being made by the client to access a resource. | This best possible way to get rid of this error is to try after sometime when the number of requests being made to the server simultaneously have dropped to a number which the server is capable to handle. |
Server Errors (5xx)
These refer to the errors caused due to server misconfiguration or unavailability of a server.| Error Code | Error Name | Description | Resolution |
|---|---|---|---|
| 500 | Internal Server Error (500) | The 500 status code, or Internal Server Error, means that server cannot process the request for an unknown reason. The most common cause for this error is Server misconfiguration. | Contacting the server administrator or Re-Executing the Probe after some time may fix this error. |
| 502 | Bad Gateway (502) | The 502 status code, or Bad Gateway error, means that the server is a gateway or proxy server, and it is not receiving a valid response from the backend servers that should actually fulfil the request. | Some common resolution steps for 502 errors include contacting the server administrator and:
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| 503 | Service Unavailable (503) | The 503 status code, or Service Unavailable error, means that the server is either under maintenance or is out of capacity/resources to serve the request. | Since this indicates a shortage of resources, executing the Probe after some time can work. |
| 504 | Gateway Timeout (504) | The 504 status code, or Gateway Timeout error, means that the server is a Proxy server and it is not receiving the response from the backend server within the stipulated time. | Since this indicates an error due to timeout, executing the Probe after some time can work. In case the probe is still failing, please contact the server administrator and check for the following:
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Certificate Errors
Certificates establish the trust connection between the server and the probe.When "Ignore CA, CRL, and CN Errors" is unchecked, the probe output might return a certificate error. This usually means that the trust connection between the probe and the server cannot be established, and the site cannot be trusted.