This question already has answers here:
from origin 'xxx' has been blocked by CORS policy: [duplicate]
(2 answers)
Closed 3 years ago.
I'm trying to authenticate over OAUTH API using Axios. The initial request is just a simple GET to get the auth token.
axios.get(
"https://github.com/login/oauth/authorize?client_id=$ID"
).then((res) => { console.log(res) })
I immediately get:
...from origin 'http://localhost:3001' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
I can use an href link and it works totally fine. What could be the issue here?
In simple terms, when you are using the anchor tag, it is a link to the original site. When user click on a tag, user will be redirected to that site. But when an AJAX request user will stay in your site and sends an ajax request to the server(github in this case).
When using HTTP protocol there is a header call origin which will tell the backend server where user is from, see the below picture
So if server does not allow sources other than it self, this security check will be failed and the AJAX request won't be success. Please let me know if you need more clarifications and I'll be glad to help. Hope that helps.
Related
This question already has answers here:
Configure CORS response headers on AWS Lambda?
(5 answers)
Closed 3 years ago.
I have only been using AWS Lambdas for a few weeks, and I am trying to learn more about them specifically how to implement a Lambda I write on a webpage.
I have a project, I am working on in my local machine which is just a website, and some JavaScript with Axios. When I deploy my code to AWS Lambda using Serverless at the end of the output , I get a url, lets call it THE_URL. When I copy and paste this page into my browser, I am brought to a web-page which has the response on it as I expect.
But on my website, I have this script being called when I press a button,
axios
.get("THE_URL")
.then(data => console.log(data))
.catch(err => console.log(err));
And this gives me the error Access to XMLHttpRequest at 'THE_URL' from origin 'null' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. Which I have looked up and it seems is fairly common. I have researched and looked into the possible solutions that there were online, and that lead me to passing in as headers, and flagging the request so it looked like this,
axios
.get("THE_URL",
{headers: {
"Access-Control-Allow-Origin": "*"
},
withCredentials: true
}
)
But with this, I then get an error which looks like this Access to XMLHttpRequest at 'THE_URL' from origin 'null' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Which I have not been able to find any solutions for online. So I figured I would ask here, and see if any of you people have ran into any errors like this?
Thanks for reading!
The CORS header should be in your server, not the client. The server controls which client domains may access it. By adding the "*" you are allowing any site to request a resource from your server, including localhost (assuming your lambda is publicly accessible)
Update the lambda to return the Access-Control-Allow-Origin: * header.
https://serverless.com/framework/docs/providers/aws/events/apigateway/#enabling-cors
This question already has answers here:
How does the 'Access-Control-Allow-Origin' header work?
(19 answers)
No 'Access-Control-Allow-Origin' header is present on the requested resource—when trying to get data from a REST API
(26 answers)
Closed 4 years ago.
(translated by Google)
Hello
I have a doubt regarding the use of fetch
From my server, I access images that are hosted on another server (such as a CDN)
This piece of code works correctly. The image is shown.
var img = document.getElementById( obj );
img.src = data-src;
// data-src has the url of the image https://serverCDN/image/bar/foo.jpg
However, within the same script, same servers, same image involved, the following code does not work.
Returns the error "Access to fetch at 'https://serverCDN/image/bar/foo.jpg' from origin 'http://myServer' has been blocked by CORS policy: No 'Access -Control-Allow-Origin 'header is present on the requested resource. If an opaque response serves your needs, set the request's mode to' no-cors' to fetch the resource with CORS disabled."
fetch ( data-src ), {})
.then (
function (res) {
console.log (res)
}
);
Because the first piece of code works and the second does not?
I'm confused.
I would be interested in using fetch, because I need to access the RESPONSE HEADERS sent by the CDN server
EDIT (FOR DUPLICATED TAG)
I undestand the CORS concept, but
The Dude is...Why, the first piece of code works and the second does not?
The problem is, that the server on https://servercdn/image/bar/foo.jpg does not send a Cross Origin header. By default, JavaScript XMLHttpRequests (XHR) are bound to the same domain. You can change this behaviour by adding cross origin HTTP header to the target server.
Or a simpler way: Use jsonp: https://www.w3schools.com/js/js_json_jsonp.asp
This question already has answers here:
How does the 'Access-Control-Allow-Origin' header work?
(19 answers)
No 'Access-Control-Allow-Origin' header is present on the requested resource—when trying to get data from a REST API
(26 answers)
Closed 4 years ago.
Hi I'm new to javascript and API calls and I'm trying to make an API call using the following javascript code:
var url = 'https://labs.bible.org/api/?
passage=random&type=json&callback=myCallBackFcn';
var ourRequest = new XMLHttpRequest();
ourRequest.open('GET', url);
ourRequest.onload = function(){
console.log(ourRequest.responseText);
};
ourRequest.send();
When I refresh my page I get the following error:
Failed to load
https://labs.bible.org/api/?passage=random&type=json&callback=myCallBackFcn:
No 'Access-Control-Allow-Origin' header is present on the requested
resource. Origin 'null' is therefore not allowed access.
Can anyone help me with this? Also, can you explain exactly how to fix it?
You have a cross-origin issue, let's explain it.
Browser downloaded js file from example.com website, now js file wants to make ajax to xyz.org website, this is a cross-origin request and so the browser asks xyz.org "do you allow example.com to access your resources"? the browser knows the answer from 'Access-Control-Allow-Origin' Response header.
But xyz.org didn't send this header so the browser assumed xyz.org doesn't want anyone but him to access his resources so the browser just refuses your request.
Note that cross-origin request happens too when you access js file in a URL beginning with file:// and origin here is set to null because js isn't downloaded from any server yet origin null is different from xyz.org.
Solution: if you control xyz.org just make it add Access-Control-Allow-Origin to response headers, you can look the internet for value format for this header.
If it's a third party website you have to call its admins and if they refuse to add the header then you simply have no solution in pure js but hey only browsers respects this policy, if you make a desktop application then it doesn't care and an example of this is Postman the REST APIs tester.
I am trying to read online html document and parse some data from it using Angular. The problem is I am keep getting an error about cors. My code for reading html document is:
loadParsingData(htmlToParse:String){
let retVal = this.http.get(htmlToParse.toString())
.map(res => res.text())
return retVal; }
When I try to test this code I expect to get html document from given website (for example imdb most popular movies) as argument, but all I get is:
XMLHttpRequest cannot load
http://www.imdb.com/chart/moviemeter?ref_=nv_mv_mpm_8. No
'Access-Control-Allow-Origin' header is present on the requested
resource.
Can anyone please help me? Thank you in beforehand.
You can send your request through a CORS proxy instead.
Where you’re specifying the URL http://www.imdb.com/chart/moviemeter?ref_=nv_mv_mpm_8 in your code now, just replace that with this URL:
https://cors-anywhere.herokuapp.com/http://www.imdb.com/chart/moviemeter?ref_=nv_mv_mpm_8
That will cause the request to be sent to https://cors-anywhere.herokuapp.com, a proxy that will then send the request on to http://www.imdb.com/chart/moviemeter?ref_=nv_mv_mpm_8. And when that proxy gets the response, it will take it and add the Access-Control-Allow-Origin response header to it and then pass that back to your requesting frontend code as the response.
That response with the Access-Control-Allow-Origin response header is what your browser sees, so the error message the browser is showing you now goes away, and the browser allows your frontend JavaScript code to access the response.
https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS has general details on CORS, and "No 'Access-Control-Allow-Origin' header is present on the requested resource" is an answer with more details about how you can set up your own CORS proxy.
This question already has answers here:
XMLHttpRequest cannot load XXX No 'Access-Control-Allow-Origin' header
(11 answers)
Closed 6 years ago.
This confuses me a lot. Let's say I have 2 tabs open in my browser, one on http://aaa.com and another on http://bbb.com.
Let's say I make a request
$ajax({
method : 'POST',
url : 'http://aaa.com/SomeAction',
...
});
from the JavaScript console of my browser. The way I understand cross-origin policy is that the server only allows that request to happen if the JS console I typed it into was the one in the tab for http://aaa.com. But how does the server know that? Does my browser send it a header that tells it where the request is coming from?
is that the server only allows that request to happen if the JS
console I typed it into was the one in the tab for http://aaa.com
Not true.
Nothing stops example.com from sending an AJAX request to example.org. The Same Origin Policy however will prevent example.com from reading the response returned.
The Same Origin Policy is enforced in the client-side browser, not on the server.