#Why does origin download so slow Patch
#Why does origin download so slow code

The site will do regular requests with preflight requests when loading the iframe fails.

#Why does origin download so slow code

The code using fetch does not need to know about the document.domain changes. Now we can use Fetch API as usual to make requests to the API without any preflight requests. This overrides the current window fetch function with the fetch function that was loaded from the API domain. The second line includes the page we exposed in the API as an iframe. This allows us to execute JavaScript between the frames. Now both API and APP are using the same origin. Now in the APP we can add following two lines of code: document.domain = вЂвЂ™ ДЇirst we change the current document domain to. We override the parent window fetch function with the current window fetch function.It is possible to change to, but it is not possible to change it to nor. Browsers allow changing the current document.domain to a super-domain. There are two important things to notice here: First we need to expose a new endpoint in our API that returns the following HTML. However, we can avoid the preflight request with a simple iframe. Making a request from the APP to the API will trigger a preflight request because the subdomains are different. Lets say you have a public API on and a user-facing site (the APP) on. This solution works only when both the site and the server share the same base domain. Avoiding CORS RequestsДЄs usual in the world of web development, there are ways to work around the restrictions imposed by browsers. However, we are committed to having clean APIs so this is not an option for us. We could make it work by sending _method attribute to route the requests and by using text/plain content type, despite the contents being in JSON format.

#Why does origin download so slow Patch

We also use other HTTP methods like PUT, PATCH and DELETE. In our case, most of our APIs expect JSON payloads. Content-Type header is set to application/x-www-form-urlencoded, multipart/form-data or text/plain.Only Accept, Accept-Language, Content-Language and Content-Type headers are used.A request is considered simple if it follows these rules: Caching DELETE /articles/1 still means that the browser has to do a new preflight request when invoking DELETE /articles/2.Д¬ORS specification says that preflight requests are not mandatory for Simple Requests. Many RESTful URLs include some kind of resource ID in the URL.Chrome sets an upper limit for preflight request cache expiration which is 10 minutes.Such delays are very noticeable to us and to our clients.Д®ven though browsers have mechanisms to reduce the performance impact they all fall short in most of the real use cases: Use caching?

This preflight request added almost an extra half of a second delay. The picture on the left shows timings of a preflight request that was sent from an Eastern European location to a server which was located in the Western US. In a development environment where everything is running on the same machine, this request is almost instant, but the story is very different in the wild world.