OPTIONS

The HTTP OPTIONS method is used to describe the communication options for the target resource. The client can specify a URL for the OPTIONS method, or an asterisk (*) to refer to the entire server.

Syntax

OPTIONS /index.html HTTP/1.1
OPTIONS * HTTP/1.1

Examples

Identifying allowed request methods

To find out which request methods a server supports, one can use curl and issue an OPTIONS request:

curl -X OPTIONS http://example.org -i

The response then contains an Allow header with the allowed methods:

HTTP/1.1 204 No Content
Allow: OPTIONS, GET, HEAD, POST
Cache-Control: max-age=604800
Date: Thu, 13 Oct 2016 11:45:00 GMT
Expires: Thu, 20 Oct 2016 11:45:00 GMT
Server: EOS (lax004/2813)
x-ec-custom-error: 1

Preflighted requests in CORS

In CORS, a preflight request with the OPTIONS method is sent, so that the server can respond whether it is acceptable to send the request with these parameters. The Access-Control-Request-Method header notifies the server as part of a preflight request that when the actual request is sent, it will be sent with a POST request method. The Access-Control-Request-Headers header notifies the server that when the actual request is sent, it will be sent with a X-PINGOTHER and Content-Type custom headers. The server now has an opportunity to determine whether it wishes to accept a request under these circumstances.

OPTIONS /resources/post-here/ HTTP/1.1 
Host: bar.other 
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 
Accept-Language: en-us,en;q=0.5 
Accept-Encoding: gzip,deflate 
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7 
Connection: keep-alive 
Origin: http://foo.example 
Access-Control-Request-Method: POST 
Access-Control-Request-Headers: X-PINGOTHER, Content-Type

The server responds with Access-Control-Allow-Methods and says that POST, GET, and OPTIONS are viable methods to query the resource in question. This header is similar to the Allow response header, but used strictly within the context of CORS.

HTTP/1.1 204 No Content
Date: Mon, 01 Dec 2008 01:15:39 GMT 
Server: Apache/2.0.61 (Unix) 
Access-Control-Allow-Origin: http://foo.example 
Access-Control-Allow-Methods: POST, GET, OPTIONS 
Access-Control-Allow-Headers: X-PINGOTHER, Content-Type 
Access-Control-Max-Age: 86400 
Vary: Accept-Encoding, Origin
Keep-Alive: timeout=2, max=100 
Connection: Keep-Alive

Specifications

Browser compatibility

See also

• Allow header
• CORS