449 Retry With

When a request lacks data the server needs to complete the operation, Microsoft IIS responds with 449 Retry With. The client must reformulate and resubmit with the missing information.

Table of Contents

Usage

The 449 Retry With status code tells the client to determine what information is missing, reformulate the request, and resubmit. The response typically includes a header or body describing the additional data the server expects, such as an Authentication token or extended session parameter.

This code is documented in the Microsoft Web Distributed Authoring and Versioning (WebDAV) extensions for IIS.

Example

A client sends a POST request to an IIS server. The server responds with 449 Retry With because the request is missing required extended information.

Request

POST /resource HTTP/1.1
Host: www.example.re
Content-Type: application/xml
Content-Length: 42

<request><action>create</action></request>

Response

HTTP/1.1 449 Retry With
Content-Type: text/html
Content-Length: 178

<html>
  <head>
    <title>Retry With</title>
  </head>
  <body>
   <p>The request is missing required information.
   Resubmit with the correct parameters.</p>
  </body>
</html>

How to fix

Inspect the response body for a description of the missing data. IIS returns an entity body explaining the exact fields, tokens, or extended parameters the server expects before completing the request.

Look for the Ms-Echo-Request header in the 449 response. The Microsoft WebDAV protocol extension uses this header to instruct the client on what data to include. The client must resubmit the original request with an Ms-Echo-Reply header containing the requested value.

Verify Authentication credentials and tokens. WebDAV operations on IIS require proper authentication. Anonymous Authentication alone is insufficient for WebDAV resources. Enable Windows Authentication or Basic Authentication in the IIS Manager for the target site or virtual directory.

Check IIS request validation settings. Request filtering rules or custom request validators block requests missing required parameters and return 449 instead of a standard 400 or 401.

Ensure the client sends all extended headers the application expects. Custom IIS applications sometimes validate for proprietary headers and return 449 when headers are absent. Review the IIS application logs (under %SystemDrive%\inetpub\logs\LogFiles) for entries tagged with substatus code details.

Standard HTTP clients do not handle 449 responses automatically. Client code interacting with IIS WebDAV endpoints needs explicit retry logic for this status code.

Code references

Windows exposes the code as a named constant in both HTTP client libraries, describing the meaning as a request worth retrying once the appropriate action has been taken.

WinHTTP and WinINet

HTTP_STATUS_RETRY_WITH

The constant is unusual among vendor status codes. Most carry no library binding at all, and application code compares the number directly.

See also

Last updated: August 17, 2026