{"json_modified": "2016-08-31T04:14:28.067229", "uuid": "d5186572-f51b-4474-a79b-92bf06f40ba7", "title": "412 Precondition Failed", "url": "/en-US/docs/Web/HTTP/Status/412", "tags": ["Reference", "Status code", "HTTP", "Error"], "translations": [], "modified": "2016-08-31T04:14:28", "label": "412 Precondition Failed", "localization_tags": [], "locale": "en-US", "id": 192703, "last_edit": "2016-08-31T04:14:23", "summary": "The HTTP <code><strong>412</strong></code><strong><code> Precondition Failed</code></strong> client error response code indicates that access to the target resource has been denied. This happens with conditional requests on methods other than <a href=\"/en-US/docs/Web/HTTP/Methods/GET\" title=\"The GET method requests a representation of the specified resource. Requests using GET should only retrieve data.\"><code>GET</code></a> or <a href=\"/en-US/docs/Web/HTTP/Methods/HEAD\" title=\"The HTTP HEAD method requests the headers that are returned if the specified resource would be requested with an HTTP GET method. Such a request can be done before deciding to download a large resource to save bandwidth, for example.\"><code>HEAD</code></a> when the condition defined by the <a href=\"/en-US/docs/Web/HTTP/Headers/If-Unmodified-Since\" title=\"The If-Unmodified-Since request HTTP header makes the request conditional: the server will send back the requested resource, or accept it in the case of a POST or another non-safe method, only if it has not been last modified after the given date. If the request has been modified after the given date, the response will be a 412 (Precondition Failed) error.\"><code>If-Unmodified-Since</code></a> or <a href=\"/en-US/docs/Web/HTTP/Headers/If-None-Match\" title=\"The If-None-Match HTTP request header makes the request conditional. For GET and HEAD methods, the server will send back the requested resource, with a 200 status, only if doesn't have a ETag matching the given one. For other methods, the request will be processed only if the eventually existing resource's ETag doesn't match any of the values listed.\"><code>If-None-Match</code></a> headers is not fulfilled. In that case, the request, usually an upload or a modification of a resource, cannot be made and this error response is sent back.", "sections": [{"id": "Quick_Links", "title": null}, {"id": "Status", "title": "Status"}, {"id": "Specifications", "title": "Specifications"}, {"id": "Browser_compatibility", "title": "Browser compatibility"}, {"id": "See_also", "title": "See also"}], "slug": "Web/HTTP/Status/412", "review_tags": []}