Option Requests

Explanation#

What Are OPTIONS Requests?#

An OPTIONS request is an HTTP method used to describe the communication options available for a specific resource or server. When a client makes an OPTIONS request, the server responds with the supported HTTP methods (e.g., GET, POST, PUT) and other information about the resource. This allows the client to understand what actions it can take before making an actual request.

Why Are OPTIONS Requests Important?#

In the context of CORS, browsers automatically send OPTIONS requests—called preflight requests—to determine if the actual request is safe to send. This ensures the server explicitly permits the intended action, preventing unauthorized cross-origin operations.

How Are OPTIONS Requests Used?#

An OPTIONS request is made by setting the HTTP method to OPTIONS. For example:

OPTIONS /example HTTP/1.1
Host: www.example.com

The server then responds with headers that describe the supported methods and other relevant information:

HTTP/1.1 200 OK
Access-Control-Allow-Methods: GET, POST, OPTIONS

This response informs the client of what it can and cannot do with the resource, making OPTIONS requests useful for preflight checks, understanding server capabilities, and ensuring compliance with CORS policies.

Usage#

Revali Server automatically handles OPTIONS requests for you.

import 'package:revali_router/revali_router.dart';

@Controller('users')
class MyController {
    @Get()
    void user() {}

    @Post()
    void save() {}
}

In the example above, when a client sends an OPTIONS request to /users, Revali Server automatically responds with a 200 OK, along with the allowed methods for the resource.

Access-Control-Allow-Methods: GET, POST, OPTIONS