EC
449
HTTPERRORNotable4xx Client Error (Unofficial)HIGH confidence

Retry With

Production Risk

Low — only encountered in Microsoft IIS/SharePoint environments.

What this means

449 Retry With is a Microsoft IIS extension indicating that the server cannot honour the request because the client has not provided sufficient information. The client should retry the request with the appropriate additional information.

Why it happens
  1. 1The request is missing required information that the server needs to process it.
  2. 2A Microsoft-specific middleware or handler requires additional context not present in the request.
  3. 3Typically seen in SharePoint or other Microsoft web applications.
How to reproduce

A client requests a resource on a Microsoft IIS/SharePoint server without providing required authentication context or metadata.

trigger — this will error
trigger — this will error
GET /sharepoint/document.docx HTTP/1.1
Host: intranet.company.com
# Missing required context headers

expected output

HTTP/1.1 449 Retry With

Fix

Retry the request with the required additional information

WHEN The response body or headers indicate what information is missing.

Retry the request with the required additional information
// Check the response body for details about what to include
// Then retry with appropriate headers or body content

Why this works

IIS typically includes information in the response about what the client should provide.

What not to do

✕ Do not use 449 in new application designs

Use standard codes like 400 (Bad Request) with a descriptive body instead.

Version notes
IIS / SharePoint

Microsoft-specific; not part of any IETF standard.

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