Allow Access-Control-Allow-Origin header using HTML5 fetch API

no 'access-control-allow-origin' header is present on the requested resource.
set the request's mode to 'no-cors' to fetch the resource with cors disabled.
access to fetch at from origin has been blocked by cors policy
cors header 'access-control-allow-origin' missing
access-control-allow-origin localhost
access-control-allow-methods
fetch cors header
access-control-allow-headers

I am using HTML5 fetch API.

var request = new Request('https://davidwalsh.name/demo/arsenal.json');

fetch(request).then(function(response) {
    // Convert to JSON
    return response.json();
}).then(function(j) {
    // Yay, `j` is a JavaScript object
    console.log(JSON.stringify(j));
}).catch(function(error) {
    console.log('Request failed', error)
});

I am able to use normal json but unable to fetch the data of above api url. It throws error:

Fetch API cannot load https://davidwalsh.name/demo/arsenal.json. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

Like epascarello said, the server that hosts the resource needs to have CORS enabled. What you can do on the client side (and probably what you are thinking of) is set the mode of fetch to CORS (although this is the default setting I believe):

fetch(request, {mode: 'cors'});

However this still requires the server to enable CORS as well, and allow your domain to request the resource.

Check out the CORS documentation, and this awesome Udacity video explaining the Same Origin Policy.

You can also use no-cors mode on the client side, but this will just give you an opaque response (you can't read the body, but the response can still be cached by a service worker or consumed by some API's, like <img>):

fetch(request, {mode: 'no-cors'})
.then(function(response) {
  console.log(response); 
}).catch(function(error) {  
  console.log('Request failed', error)  
});

Fetch: Cross-Origin Requests, The server must grant access to the requested resource to your remote domain by sending a Access-Control-Allow-Origin response header. The browser only returns the response if the server returns an Access-Control-Allow-Origin header specifying that the origin has permission to request the resource. In practice, servers that expect

I had my front-end code running in http://localhost:3000 and my API(Backend code) running at http://localhost:5000

Was using fetch API to call the API. Initially, it was throwing "cors" error. Then added this below code in my Backend API code, allowing origin and header from anywhere.

let allowCrossDomain = function(req, res, next) {
  res.header('Access-Control-Allow-Origin', "*");
  res.header('Access-Control-Allow-Headers', "*");
  next();
}
app.use(allowCrossDomain);

However you should restrict the you origins in case of other environments like stage, prod.

Working with the Fetch API | Web, The Fetch API provides a JavaScript interface for accessing and manipulating parts Note that mode: "no-cors" only allows a limited set of headers in the request: browsers to send a request with credentials included, even for a cross-​origin  Cors header 'access-control-allow-origin' (Django-cors-headers) Django Rest framework API Tutorial [15] Loading Autoplay When autoplay is enabled, a suggested video will automatically play next.

This worked for me :

npm install -g local-cors-proxy

API endpoint that we want to request that has CORS issues:

https://www.yourdomain.com/test/list

Start Proxy:

lcp --proxyUrl https://www.yourdomain.com

 Proxy Active 

 Proxy Url: http://www.yourdomain.com:28080
 Proxy Partial: proxy
 PORT: 8010

Then in your client code, new API endpoint:

http://localhost:8010/proxy/test/list

End result will be a request to https://www.yourdomain.ie/test/list without the CORS issues!

fetch API cannot load error with cors in chrome/firefox · Issue #301 , Return the values of all headers in list whose name is a Access-Control-​Request-Method `; ` Connection Keep-Alive `; ` Origin `; ` Referer `; ` TE `; ` Trailer `; ` Transfer-Encoding `; ` Upgrade `; ` Via ` APIs using fetch that allow control over headers by developers, such as XMLHttpRequest . The proxy makes the request to that site, gets the response, adds the Access-Control-Allow-Origin response header and any other CORS headers needed, then passes that back to your requesting code. And that response with the Access-Control-Allow-Origin header added is what the browser sees, so the browser lets your frontend code actually access

I know this is an older post, but I found what worked for me to fix this error was using the IP address of my server instead of using the domain name within my fetch request. So for example:

#(original) var request = new Request('https://davidwalsh.name/demo/arsenal.json');
#use IP instead
var request = new Request('https://0.0.0.0/demo/arsenal.json');

fetch(request).then(function(response) {
    // Convert to JSON
    return response.json();
}).then(function(j) {
    // Yay, `j` is a JavaScript object
    console.log(JSON.stringify(j));
}).catch(function(error) {
    console.log('Request failed', error)
});

Cross-Origin Resource Sharing (CORS), Cross-origin resource sharing (CORS) is a mechanism that allows restricted resources on a The specification for CORS is included as part of the WHATWG'​s Fetch Living Standard. Note that in the CORS architecture, the Access-​Control-Allow-Origin header is being set by the external web service (service.​example.com)  If the server agrees to accept the request with credentials, it should add a header Access-Control-Allow-Credentials: true to the response, in addition to Access-Control-Allow-Origin. For example: 200 OK Access-Control-Allow-Origin: https://javascript.info Access-Control-Allow-Credentials: true

If you are use nginx try this

#Control-Allow-Origin access

    # Authorization headers aren't passed in CORS preflight (OPTIONS) calls. Always return a 200 for options.
    add_header Access-Control-Allow-Credentials "true" always;
    add_header Access-Control-Allow-Origin "https://URL-WHERE-ORIGIN-FROM-HERE " always;
    add_header Access-Control-Allow-Methods "GET,OPTIONS" always;
    add_header Access-Control-Allow-Headers "x-csrf-token,authorization,content-type,accept,origin,x-requested-with,access-control-allow-origin" always;

    if ($request_method = OPTIONS ) {
        return 200;
    }

Using Fetch, In this article, we explain what Cross-Origin Resource Sharing how to avoid errors associated with it and the Access-Control-Allow-Origin header. set the request's mode to 'no-cors' to fetch the resource with CORS disabled. You can do it if you use Fetch API by setting the mode parameter to no-cors:  If Access-Control-Allow-Origin not available in response header, browser disallow to use response in your JavaScript code and throw exception at network level. You need to configure cors at your server side.

Fetch Standard, Learn how to fetch data from another domain by using CORS with all modern browsers. If a response contains the Access-Control-Allow-Origin header, and if the often load data by using JavaScript and a greater number of modern web APIs are that rely on either A) Flash under the covers, or B) some voodoo HTML5. i've created a small API using Node/Express and trying to pull data using Angularjs but as my html page is running under apache on localhost:8888 and node API is listen on port 3000, i am getting t

Cross-origin resource sharing, No 'Access-Control-Allow-Origin' header is present on the requested resource—when trying to get data from a REST API 0 CORS: How to set 'Access-Control-Allowed-Origin' request header

Cross-Origin Resource Sharing: Access-Control-Allow-Origin, CORS is a browser feature. Servers need to opt into CORS to allow browsers to bypass same-origin policy. Your server would not have that same restriction and be able to make requests to any server with a public API.

Comments
  • The 3rd party server needs to set it, there is nothing you can do on the clientside.
  • @epascarello: We can do at the client side. Behind the scene, XHR Request is going on. Please check this https://davidwalsh.name/fetch
  • can you elaborate on "However this still requires the server to enable CORS as well, and allow your domain to request the resource."? I've been unsuccessfully looking for instructions to do that.
  • @jayscript the overall process looks like this: on the client, a cross origin request is made with javascript. In the case of the fetch API, 'cors' mode tells the browser that its okay to make this request. If you had 'no-cors' mode instead, the browser would stop the request, because it is not to your app's origin. The server will receive the request and respond. The browser confirms that the response has the appropriate CORS headers, and if so, allows the response to be read. If the headers are not present, the browser will throw an error.
  • @jayscript this MDN article goes into detail. Essentially, one your server you need set these headers: "Access-Control-Allow-Origin: foo.example", "Access-Control-Allow-Methods: POST, GET, OPTIONS", "Access-Control-Allow-Headers: X-PINGOTHER, Content-Type", which enable origins, methods, and headers respectively. Typically '*' is used for the origin header.You can also check this Google document and associated codelab to learn about the Fetch API: developers.google.com/web/ilt/pwa/working-with-the-fetch-api
  • Thank you! That help me understand that it is impossible to fetch data from the API server that has a different origin when the API server does not contain any headers. In the particular case I was dealing with, I had access to the API server code and was able to add headers by myself, which enabled fetching.
  • This is dumb, what's the security issue with NO sending cookies and thus allowing CORS?
  • this is a terrible answer. this is a massive security issue. if you are reading this, PLEASE DO NOT DO THIS.
  • This is ly for the local setup. For example to do a quick pic kinda. Yes there is a security risk if the same goes for other deployable environments. For local I feel it doesn't."However you should restrict the you origins in case of other environments like stage, prod"
  • thanks. saved me a lot of wasted time
  • How can you know if it is OP's server and it is written in NodeJs?
  • If you have created a node server (development mode), you can use that method to use fetch in js.