HTTP Status Code 449 – Retry With

The HTTP status code 449 Retry With is a Microsoft extension to the HTTP standard. It is used by Microsoft servers, such as Internet Information Services (IIS), to instruct the client to retry the request with specific conditions. This status code is typically encountered when a server requires additional information or changes in the request, often due to missing or invalid data.

Example 1: Missing Required Headers

Consider an API that requires a specific header for authentication. If the client sends a request without this header, the server might respond with a 449 status code to prompt the client to retry with the necessary authentication headers.


// Client Request without authentication header
GET /secure-data HTTP/1.1
Host: api.example.com

// Server Response
HTTP/1.1 449 Retry With
Content-Type: application/json
Retry-After: 3600

{
“error”: “Missing authentication header. Please retry with the required header.”
}

In this example, the server returns a 449 status code, indicating that the request should be retried with the appropriate authentication header.

Example 2: Incorrect Content-Type

Another scenario is when a client submits data in an incorrect format. The server might respond with a 449 status code, asking the client to resend the request with the correct ‘Content-Type’.


// Client Request with incorrect content type
POST /submit-form HTTP/1.1
Host: api.example.com
Content-Type: text/plain

{ “name”: “John Doe”, “age”: 30 }

// Server Response
HTTP/1.1 449 Retry With
Content-Type: application/json
Retry-After: 120

{
“error”: “Invalid Content-Type. Please retry with ‘application/json’.”
}

Here, the server instructs the client to resend the request with the correct ‘Content-Type’ header to ensure data is processed correctly.

Example Scenario 3

# Client sends a request example.
GET /example HTTP/1.1
Host: www.example.com

# Server Response
HTTP/1.1 449 449 Retry With
Date: Wed, 09 Oct 2024 23:08:13 GMT
Server: ExampleServer/1.0
Content-Type: application/json

{
    "error": "Description of the error for 449"
}

Example Scenario 4

# Client sends another example request.
POST /another-example HTTP/1.1
Host: www.example.com

# Server Response
HTTP/1.1 449 449 Retry With
Date: Wed, 09 Oct 2024 23:08:13 GMT
Server: ExampleServer/1.0
Content-Type: application/json

{
    "error": "Detailed message for 449"
}

Summary

The 449 Retry With status code is a useful mechanism for servers to handle requests that are missing required parameters or headers. It helps guide clients in correcting their requests, ensuring that communication between client and server is efficient and effective. While not part of the official HTTP standard, it is a practical extension used in specific environments like Microsoft’s IIS.