428 Precondition Required

The HTTP 428 Precondition Required client error response status code indicates that the server requires the request to be conditional.

Typically, a 428 response means that a required precondition header such as {{HTTPHeader("If-Match")}} is missing. When a precondition header does not match the server-side state, the response should be {{HTTPStatus("412", "412 Precondition Failed")}}.

Status

428 Precondition Required

Examples

Missing precondition in request

A client has fetched a resource my-document from the server, updated it locally, and then tries to send the updated document back to the server:

PUT /docs/my-document HTTP/1.1
Host: example.com
Content-Type: application/json

{
  […]

The server implementation requires that all {{HTTPMethod("PUT")}} requests for the specific path or type of documents must be conditional and sends a 428 response:

HTTP/1.1 428 Precondition Required
Date: Wed, 26 Jun 2024 12:00:00 GMT
Server: Apache/2.4.1 (Unix)
Content-Type: application/json

{
  "code": "MissingPrecondition",
  "message": "Updating documents requires a precondition header.",
}

Specifications

{{Specifications}}

See also

• HTTP response status codes
• HTTP conditional requests
• Conditional headers: {{HTTPHeader("If-Match")}}, {{HTTPHeader("If-None-Match")}}, {{HTTPHeader("If-Modified-Since")}}, {{HTTPHeader("If-Unmodified-Since")}}, {{HTTPHeader("If-Range")}}
• {{HTTPStatus(412)}}