The HTTP Status Code 412 indicates that the server failed to fulfill one of the client’s request header preconditions.
When the browser checks on the server, one or more of the criteria specified in the request header fields were found to be untrue. This causes status code 412 precondition failed error.
Status code 412 allows the client to set preconditions on the current state of the resource (its current representations and metadata) and therefore prohibit the request method from being used if the target resource is in an unexpected state.
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Status
412 Precondition Failed
Examples
ETag: "33a64df551425fcc55e4d42a148795d9f25f89d4"
ETag: W/"0815"
Specifications
Browser compatibility

Full Support
412 Code References
Rails HTTP Status Symbol :precondition_failed
Go HTTP Status Constant http.StatusPreconditionFailed
Symfony HTTP Status Constant Response::HTTP_PRECONDITION_FAILED
Python2 HTTP Status Constant httplib.PRECONDITION_FAILED
Python3+ HTTP Status Constant http.client.PRECONDITION_FAILED
Python3.5+ HTTP Status Constant http.HTTPStatus.PRECONDITION_FAILED
FAQs
When should I use HTTP 412?
When a request is conditional and the condition isn’t satisfied, status code 412 is used.
When any preconditions fail, the response status code 412 (Precondition Failed) is generally used. Some pre-conditions used in headers are:
(If-Match, If-Modified-Since, If-None-Match, If-Range, If-Unmodified-Since
)
What is a 412 status code?
The HTTP Status Code 412 indicates that the server failed to fulfill one of the client’s request header preconditions.
Related Post:
HTTP Status Code 300-Multiple Choices
HTTP Status Code 204 – No Content
HTTP Status Code 203 – Non-authoritative Information
HTTP Status Code 207 Multi-Status
HTTP Status Code 208 Already Reported
HTTP Status Code 400 Bad Request
HTTP Status Code 401 Unauthorized
HTTP Status Code 403 Forbidden Error
HTTP Status Code 404 Not Found
HTTP Status Code 405 Method Not Allowed
HTTP Status Code 411 Length Required
Conclusion
I hope this article was able to help you with your doubts and queries related to the HTTP status code 412 Precondition Failed. Still, if there are any queries related to this topic, feel free to ask in the comment section, we would be happy to assist you. Thank you.
Kedar Dangal
Making a difference, Adding the sum.