This question already has answers here:
XMLHttpRequest cannot load XXX No 'Access-Control-Allow-Origin' header
(11 answers)
Closed 3 years ago.
I've found simple tutorial how to make cross domain json call here
And it works perfectly fine, so i decided to use this example, just change url from:
var url = "http://api.myjson.com/bins/23xvb";
to
var url = "http://dl.sniper.pl/test.json"
Unfortunately changing it returns such an error (in chrome):
XMLHttpRequest cannot load http://dl.sniper.pl/test.json. Response to
preflight request doesn't pass access control check: No
'Access-Control-Allow-Origin' header is present on the requested
resource. Origin 'null' is therefore not allowed access.
Googling that error didnt provide any answers to find a solution so here's the question:
Why i get such an error and how to solve it?
The http://dl.sniper.pl/ server must be configured to send the Access-Control-Allow-Origin response header in responses to requests for http://dl.sniper.pl/test.json.
But because that server isn’t sending the Access-Control-Allow-Origin response header, your browser is refusing to allow your frontend JavaScript code to access that response.
So you either nust configure the http://dl.sniper.pl/ server to send Access-Control-Allow-Origin or else you can make the request through a CORS proxy.
There’s an open CORS proxy you can make you request through by changing your code to this:
var url = "https://cors-anywhere.herokuapp.com/http://dl.sniper.pl/test.json"
That sends the request through the open CORS proxy https://cors-anywhere.herokuapp.com which adds the Access-Control-Allow-Origin response header to it and then passes that back to your requesting frontend code as the response.
That response with the Access-Control-Allow-Origin response header is what the browser sees, so the browser allows your frontend JavaScript code to actually access the response.
You can also easily set up your own CORS proxy using https://github.com/Rob--W/cors-anywhere/
See https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS for an explanation of how browsers behave when you send cross-origin requests frontend JavaScript code using XHR or the Fetch API or AJAX methods from JavaScript libraries—and for details about what response headers must be received in order for browsers to allow frontend code to access the responses.
you should configure you server todo this in your htaccess
u need something like this
<RequireAll>
Require all granted
</RequireAll>
Related
I am trying to access a Google Apps Script WebAPI from my website using javascript to pass some value and create an excel file and download it through this API.
I tried 2 following way:
Using POST request with $.post.
My values are many. So, at first, I use a POST request with a body is JSON of list values. Browser rejects API response, because of CORS error.
I researched about CORS to understand it. At some topics, I found a solution is the following second way.
Access to XMLHttpRequest at 'https://script.google.com/macros/s/xxxxxxx' from origin 'https://example.com' 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.
Using GET request with $.getJSON.
I pass JSON of list values to URL parameter and make GET request. It worked fine.
var url = 'https://script.google.com/macros/s/' + api_id + '/exec?' + request_parameter_string;
$.post(url, payload, function(data, textStatus) {
// Do something
}, 'json');
$.getJSON(url, function(json_result) {
// Do something
})
.fail(function() {
// Do something
});
What I do not understand is why? Why it works with getJSON but not work with post?
I think CORS work with both of GET and POST requests. And I checked the response header with Postman. The headers are the same Access-Control-Allow-Origin →*.
I think have something is different inside getJSON and post functions.
*UPDATE: Update POST CORS error message.
GET requests are not bound by CORS we can host images and static files in CDN which is different from the origin and would help in improving the performance by caching and making parallel requests.
Similarly GET is used for serving ads, trackers and analytics from third party domains as well.
More information about Same Origin Policy and GET is at https://security.stackexchange.com/a/16221/9517
How the browsers identify Other HTTP Verbs are allowed for the cross origin request is elaborated # https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request
This question already has answers here:
Why doesn't adding CORS headers to an OPTIONS route allow browsers to access my API?
(36 answers)
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.
im trying to make a simple request to an API
fetch('someurl').then((data) => console.log(data))
but im getting the classic No 'Access-Control-Allow-Origin' header is present on the requested resource.
how can I fix this on the client side? or is the only way to fix it for the API author to change it and add the correct response headers?
To deepen you understand on CORS have a look at MDN's article on Cross-Origin Resource Sharing (CORS). It's pretty extensive.
Using jsonP you would be able to work around this when making simple GET requests. See also this older, short and sweet article that explains it in more detail. How JSONP Works.
The Wikipedia Definition of JSONP is as follows:
a communication technique used in JavaScript programs which run in Web
browsers. It provides a method to request data from a server in a
different domain, something prohibited by typical web browsers because
of the same origin policy.
With that in mind, let look at the following example and make the request.
$(document).ready(function() {
$.getJSON("https://jsonplaceholder.typicode.com/users?callback=?", function(json){
console.log('getJSON call: ', json);
});
})
FETCH does not support jsonp
After a bit of research, it does turn out that the Fetch API does not support jsonP requests. If you have a look at this jsFiddle example you'll see that the $.getJSON call returns data when used with the suffix ?callback=? while the 'fetch()' call fails and returns a CORS message. Open the console to see the result of both calls.
Your question in the comments
Also, do you know why fetch({ url : 'https://randomurl" }) would not
get a CORS blockage but fetch('https://randomurl') would?
The first argument you provide to fetch is a string/URL, the second (optional) argument can be an options object {}. Because you provide an object as the first argument, that URL cannot be found. The reason why it doesn't give you a CORS blockage is because you provided an invalid URL, which returns a 404 status. Fetch deals with page cannot be found errors by returning a 200 OK status and in the JSON returned it will provide you with more info.
The Promise returned from fetch() won’t reject on HTTP error status
even if the response is an HTTP 404 or 500. Instead, it will resolve
normally (with ok status set to false), and it will only reject on
network failure or if anything prevented the request from completing.
Source: MDN docs
I hope this helped a bit in broadening your understanding of CORS and the how Fetch works.
You can find some workaounds in Why does my JavaScript get a "No 'Access-Control-Allow-Origin' header is present on the requested resource" error when Postman does not? but you can't solve the problem from the client. It must be solved on server by setting correct headers that allow it...
I'm trying to access the Deezer API from localhost, but I'm keep getting the following error:
Fetch API cannot load http://api.deezer.com/search/track/autocomplete?limit=1&q=eminem.
Response to preflight request doesn't pass access control check: 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.
localhost's response's headers does have Access-Control-Allow-Origin header
(Access-Control-Allow-Origin:*).
I'm using fetch like:
fetch('http://api.deezer.com/search/track/autocomplete?limit=1&q=eminem').
What am I doing wrong?
You can make the request through a public CORS proxy; to do that try changing your code to:
fetch('https://cors-anywhere.herokuapp.com/http://api.deezer.com/search/track/autocomplete?limit=1&q=eminem')
That sends the request through https://cors-anywhere.herokuapp.com, which forwards the request to http://api.deezer.com/search/track/autocomplete?limit=1&q=eminem and then receives the response. The https://cors-anywhere.herokuapp.com backend adds the Access-Control-Allow-Origin header to the response and passes that back to your requesting frontend code.
The browser will then allow your frontend code to access the response, because that response with the Access-Control-Allow-Origin response header is what the browser sees.
You can also set up your own CORS proxy using https://github.com/Rob--W/cors-anywhere/
For details about what browsers do when you send cross-origin requests from frontend JS code using XHR or the Fetch API or AJAX methods from JavaScript libraries—and details about what response headers must be received in order for browsers to allow frontend code to access the responses—see https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS.
For now, it is impossible to make this request. You can proxy request to API from your own backend or use jsonp. Here is a library with fetch-like syntax https://github.com/camsong/fetch-jsonp. Usage example https://jsfiddle.net/4dmfo0dd/1/
fetchJsonp('https://api.deezer.com/search/track/autocomplete?limit=1&q=eminem&output=jsonp')
.then(function(response) {
return response.json();
})
.then(json => console.log(json))
.catch(function(error) { console.log(error); });
CORS or Cross Origin requests made to servers
http://api.deezer.com/search/track/autocomplete?limit=1&q=eminem
in this case, have a preflight check enabled by all modern browsers.
and usually fail, if the server does not respond with Access-control headers.
In case of a fetch too, since you are basically fiddling with Javascript ,
You Need the Server to respond with Access-control-Allow-Origin Headers, which are flexible.
You Can not do Much about it Unless, the API itself becomes flexible and more open.
You however can Use fetch with mode set to no-cors
IFFF you only wish to cache the result of the request you make, to serve as a response, and not consume it yourself
Read Opaque Responses
No-CORS Definition
no-cors — Prevents the method from being anything other than HEAD, GET or POST. If any ServiceWorkers intercept these requests, they may not add or override any headers except for these. In addition, JavaScript may not access any properties of the resulting Response. This ensures that ServiceWorkers do not affect the semantics of the Web and prevents security and privacy issues arising from leaking data across domains
Medium has an RSS feed available at https://medium.com/feed/[#username]. I'm trying to fetch all my blog posts using an XMLHTTPRequest. When I test on local, I run into CORs errors. When I turn on CORs Chrome extension, I get a 401 error. Any ideas? Has anyone succeeded in calling Medium RSS?
To get https://medium.com/feed/[#username] content using XHR, you can make the XHR request through a proxy of some kind. For example, trying giving your current XHR code this URL:
https://cors-anywhere.herokuapp.com/https://medium.com/feed/#sideshowbarker
That’ll cause the request to go to https://cors-anywhere.herokuapp.com, a open/public CORS proxy which then sends the request on to https://medium.com/feed/#sideshowbarker.
And when that proxy gets the response, it takes it and adds the Access-Control-Allow-Origin response header to it and then passes that back to your requesting frontend code as the response.
That response with the Access-Control-Allow-Origin response header is what the 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.
Or use the code from https://github.com/Rob--W/cors-anywhere/ or such to set up your own proxy.
The reason you need a proxy is, responses from https://medium.com/feed/[#username] don’t include the Access-Control-Allow-Origin response header, so your browser will refuse to let your frontend JavaScript code access those responses cross-origin.
https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS has more details.
This is a bug.
Bug has opened. (Dan Abramov approved)
This question already has answers here:
XMLHttpRequest cannot load XXX No 'Access-Control-Allow-Origin' header
(11 answers)
Closed 5 years ago.
I'm encountering a bit of a strange issue when making an Ajax cross domain request. I get the following error in the console of chrome dev tools:
No 'Access-Control-Allow-Origin' header is present on the requested resource error
However, when I look at the network requests, it passes the browsers CORS preflight request because request changes from OPTIONS which it was when it was failing preflight request to GET, and the response is as I would get via postman. However, the Ajax failure message is triggered so even though in dev tools the request appears to succeed, I can't access the successful response via the JavaScript.
Additional info is that the file that is making the ajax request is just an HTML file with inline JavaScript that I open directly from the file directory. I'm thinking this might be my problem but couldn't find anything that explicitly says this so I am wanting confirmation.
Note with respect to the API: the appropriate access control headers are set
You have to pass some (if not all, I haven't checked) with every response, not only the response to the pre-flight OPTIONS request.