Access to XMLHttpRequest has been blocked by CORS policy

Question

I've a problem when I try to do PATCH request in an angular 7 web application. In my backend I have:

app.use((req, res, next) => {
    res.set({
        "Access-Control-Allow-Origin": "*",
        "Access-Control-Allow-Methods": "*",
        "Access-Control-Allow-Headers": "'Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token'",
    });

    next();
});

In my frontend service, I've:

  patchEntity(ent: any, id) {
    let headers = new Headers({ 'Content-Type': '*' });
    let options = new RequestOptions({ headers: headers });
    return this.http.patch('my_url', ent).map((res: Response) => res.json());
  };

The error is:

Access to XMLHttpRequest at 'my_url' from origin 'http://localhost:4200' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: It does not have HTTP ok status.

What can I to do? Thanks.

Possible duplicate of [Response to preflight request doesn't pass access control check](https://stackoverflow.com/questions/35588699/response-to-preflight-request-doesnt-pass-access-control-check) — paulsm4, Nov 12 '18 at 08:33
Wildcard for `Access-Control-Allow-Methods` is not yet supported in all browsers. Also that error message says it came back with a non-200 status, so you should see why it's erroring first — user184994, Nov 12 '18 at 08:38
@user184994 thank you, is there a different method instead Access-Control-Allow-Methods? — RikG93, Nov 12 '18 at 08:44
No, just pass the actual values, so `POST, GET, OPTIONS, PATCH` plus any others you care about — user184994, Nov 12 '18 at 08:46
Please refer to this post for answer nd how to solve this problem https://stackoverflow.com/questions/53528643/cross-origin-resource-sharing-cors-in-angular-or-angular-6-problem-while-you/53528644#53528644 — Ramesh Roddam, Nov 28 '18 at 22:09
Does this answer your question? [Node JS - CORS Issue Response to preflight request doesn't pass access control check: The value of the 'Access-Control-Allow-Origin' header](https://stackoverflow.com/questions/44736327/node-js-cors-issue-response-to-preflight-request-doesnt-pass-access-control-c) — Quentin, Jan 08 '20 at 09:14

score 24 · Accepted Answer · answered Jan 10 '20 at 21:42

24

There are two ways this can be handled:

Temporary Front-End solution so you can test if your API integration is working:

Click on window -> type run and hit enter -> in the command window copy:

chrome.exe --user-data-dir="C://Chrome dev session" --disable-web-security

This will open a new "Chrome" window where you can work easily. This is a temporary solution. Every time you will have to work with this chrome window.

Permanent solution:

In the backend code, the developer needs to add an annotation @Crossorigin right above the CRUD api call method.

Let me know if it works.

answered Jan 10 '20 at 21:42

Bitly

348
3
15

3

how can i add an annotation @Crossorigin right above the CRUD api call method. please help me on this. – theburningfire May 20 '20 at 10:16
1

@theburningfire depend on backend. If you use Flask, here is solution https://enable-cors.org/server_flask.html – Haha TTpro Oct 17 '20 at 14:50

score 4 · Answer 2 · edited Jul 03 '20 at 03:07

use this in Node

    app.use(function (req, res, next) {
    //Enabling CORS
    res.header("Access-Control-Allow-Origin", "*");
    res.header("Access-Control-Allow-Methods", "GET,HEAD,OPTIONS,POST,PUT");
    res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, 
    Accept, x-client-key, x-client-token, x-client-secret, Authorization");
      next();
    });

And in angular the request is

 auth(login): Promise<any> {
 return new Promise((resolve, reject) => {
   this._http.post('url:3000/api/auth/login', { ...login })
     .subscribe((response: any) => {
       resolve(response);
     });
 });
}

That won't help. Nothing there will make the OPTIONS request has a 200 OK response. — Quentin, Jan 08 '20 at 09:12

abranhe · Answer 3 · 2020-07-19T18:15:38.160

I ran into the same issue even though my API was using cors and had the proper headers.

So for me, the issue was that I was making an insecure request. I was accessing my API over the http protocol, and that was causing the error.

I just changed from

http://api.example.com

to https protocol

https://api.example.com

and it fixed everything.

You can also create a simple proxy on your website to forward your request to the external site. For example, if you are trying to fetch some data from your website (my-website.com) to (another-website.com) and you make a POST request, you can have cors issues, but if you fetch the data from your own domain you will be good.

Here is how to create a simple proxy forwarding the request https://stackoverflow.com/a/20354642/7602110

So instead of making request to

POST https://api.example.com/event/create

You'll want to make the request to

POST https://my-website.com/api/event/create

I know that is some extra work, and sometimes you don't have the ability to do it, but that will definitely prevent you from having cors issues.

score 1 · Answer 4 · edited Dec 08 '19 at 05:34

1

I ran into the same issue some time ago. Below piece of code worked for me at the backend. The backend was written in express, node.

app.use(function (request, response, next) {
  response.header("Access-Control-Allow-Origin", "*");
  response.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
  next();
});

edited Dec 08 '19 at 05:34

slideshowp2

38,463
29
127
255

answered Dec 08 '19 at 05:08

Sambhaji Mane

21
1
3

2

That won't help. Nothing there will make the OPTIONS request has a 200 OK response. – Quentin Jan 08 '20 at 09:12

score 1 · Answer 5 · answered Aug 16 '20 at 19:59

Your error:

Access to XMLHttpRequest at 'my_url' from origin 'http://localhost:4200' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: It does not have HTTP ok status.

My error:

Access to XMLHttpRequest at 'localhost:3000/api/todo' from origin 'http://localhost:4200' has been blocked by CORS policy: Cross origin requests are only supported for protocol schemes: http, data, chrome, chrome-extension, https.

(Even though a bit different error but i'll answer anyway)

Now two questions here:

How did i resolve my issue?

Ans. Putting 'http://' before api i used, means 'http://localhost:3000/api/todo'.

What might've caused your error?

Ans. Can't say for sure but i dont see your api url instead it says 'my_url' (comparing both errors). I thik you may've passed string instead of variable.

I'll be happy if this helps anyone. Because this cost me almost 2hr and now it's midnight(almost).

score -1 · Answer 6 · answered Jun 27 '19 at 11:58

-1

This problem is not on your frontend angular code it is related to backend,

Try below steps in your backend code :

1.npm install cors

2.put app.use(cors()) in main express route file.(enables all CORS requests)

may be it works for you.

reference link : https://expressjs.com/en/resources/middleware/cors.html

answered Jun 27 '19 at 11:58

Savan2396

94
5

That's insufficient. See https://expressjs.com/en/resources/middleware/cors.html#enabling-cors-pre-flight – Quentin Jan 08 '20 at 09:13

score -1 · Answer 7 · answered Nov 07 '19 at 16:22

If you are using Tomcat try this: full documentation

 HttpServletResponse response = (HttpServletResponse) servletResponse;
        HttpServletRequest request = (HttpServletRequest) servletRequest;

        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setHeader("Access-Control-Allow-Credentials", "true");
        response.setHeader("Access-Control-Allow-Methods", "GET, POST, PATCH, PUT, DELETE, OPTIONS, HEAD");
        response.setHeader("Access-Control-Allow-Headers", "Origin, Accept, X-Requested-With, Content-Type, "
                + "Access-Control-Request-Method, Access-Control-Request-Headers, Authorization");


        if ( request.getMethod().equals("OPTIONS") ) {
            response.setStatus(HttpServletResponse.SC_OK);
            return;
        }


        filterChain.doFilter(servletRequest, servletResponse);

Then in web.xml

<filter>
    <filter-name>cors</filter-name>
    <filter-class>classYouImplementTheCodeAbove</filter-class>
</filter>

<filter-mapping>
    <filter-name>cors</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

If you are using other go to https://enable-cors.org/server.html and search for it

"If you are using Tomcat" — They aren't. – Quentin Jan 08 '20 at 09:12 — Quentin, Jan 08 '20 at 09:12

Access to XMLHttpRequest has been blocked by CORS policy

7 Answers7