I am getting this message when trying to send a post request:
Access to XMLHttpRequest at 'http://localhost:3002/api/products/checkout' from origin
'http://localhost:4200' has been blocked by CORS policy: Request header field content-type
is not allowed by Access-Control-Allow-Headers in preflight response.
Right now I'm simply trying to send data to my backend and then log it in the console. Get requests work fine but for some reason I get that CORS error when trying post. Here is my code:
Angular code:
//api call
return this.http.post('http://localhost:3000/api/checkout', cart)
NodeJs code:
const bodyParser = require('body-parser');
const express = require('express');
const app = express();
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: false}));
app.use((req, res, next) => {
res.setHeader('Access-Control-Allow-Origin', '*');
res.setHeader(
'Access-Control-Allow-Header',
'Origin, X-Requested-With, Content-Type, Accept');
res.setHeader(
'Access-Control-Allow-Methods',
'GET, POST, PATCH, DELETE, OPTIONS');
next();
})
app.post("/api/checkout", (req, res, next) => {
const cart = req.body;
console.log(cart)
res.status(201).json()
})
module.exports = app;
In the network calls I can see that Request Headers is:
Access-Control-Request-Headers: content-type
while Response Headers is:
Access-Control-Request-Headers: Origin, X-Requested-With, Content-Type, Accept
I'm not sure if content-type being lower case has anything to do with the issue.
You should use req.set instead, just change setHeader to set only. Here is the document https://expressjs.com/en/api.html#res.set
And if you just using localhost, there's another easier option, you can use proxy. More information can be found here https://angular.io/guide/build#proxying-to-a-backend-server
I think the problem that you wrote Access-Control-Allow-Header instead of Access-Control-Allow-Headers, but I cannot test it now.
Be aware that you need to serve OPTIONS requests too. Which is just responding with an empty message body using the same headers. You can get these kind of OPTIONS requests before PUT, PATCH, DELETE from certain HTTP clients e.g. from browsers too.
I don't know what is causing this error. I set all the right headers and all the correct methods. This is my Node Js Server:
Full Error : login:1 Access to XMLHttpRequest at 'http://localhost:3000/' 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. zone-evergreen.js:2845 POST http://localhost:3000/ net::ERR_FAILED
const path = require("path");
const express = require("express");
const bodyParser = require("body-parser");
const app = express();
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use((req, res, next) => {
res.setHeader("Access-Control-Allow-Origin", "*");
res.setHeader(
"Access-Control-Allow-Headers",
"Origin, X-Requested-With, Content-Type, Accept"
);
res.setHeader(
"Access-Control-Allow-Methods",
"GET,PUT, POST, PATCH, DELETE, OPTIONS"
);
next();
});
I am sending POST request from an Angular app from http://localhost:4200 and connecting it with a MongoDB Server.
If someone could help me with this it would be great.
There are several ways to fix/workaround this.
Turn off CORS. For example: https://stackoverflow.com/questions/3102819/disable-same-origin-policy-in-chrome
Use a plugin for your browser : https://chrome.google.com/webstore/detail/allow-cors-access-control/lhobafahddgcelffkeicbaginigeejlf?hl=en
Use a proxy such as nginx. http://nginx.org/en/docs/beginners_guide.html
Go through the necessary setup for your server. This is more a
factor of the web server you have loaded on your EC2 instance
(presuming this is what you mean by "Amazon web service"). For your
specific server you can refer to the enable CORS website.
I am using a Angular 2 app and a NodeJS API. When I had the API in localhost everything was working just right, but I published my NodeJS API to a real server and it gives me that error when I try to access to any method of the API:
Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource
I was checking some anwsers from another topics here in stackoverflow and nothing has worked for me.
I've this snipped :
app.use(require("cors")());
app.use(function(req, res, next) {
res.setHeader("Access-Control-Allow-Origin", "*");
res.setHeader(
"Access-Control-Allow-Headers",
"Origin, X-Requested-With, Content-Type, Accept,responseType"
);
res.setHeader(
"Access-Control-Allow-Methods",
"POST, GET, PATCH, DELETE, OPTIONS"
);
next();
});
So I have the "*" in Access-Control-Allow-Origin header why I got the error that I don't have this header in my headers?
Thanks in advance.
Use only the middleware
var express = require('express')
var cors = require('cors')
var app = express()
app.use(cors())
more details
EDIT: Kevin B answered my question in a comment below. I added some logic to send a 200 request if an OPTIONS http request hit my API to fix the problem. Here is the code:
var allowCrossDomain = function(req, res, next) {
if ('OPTIONS' == req.method) {
res.header('Access-Control-Allow-Origin', '*');
res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,PATCH,OPTIONS');
res.header('Access-Control-Allow-Headers', 'Content-Type, Authorization, Content-Length, X-Requested-With');
res.send(200);
}
else {
next();
}
};
router.use(allowCrossDomain);
Original Question:
I currently am trying to get an Ionic 2 application running on my localhost to be able to send data to an Express 4 application. It works when I send requests without an authorization header. However, once I added auth headers, my API began to throw errors. I have done my research and have tried to implement what I found here: (https://stackoverflow.com/a/15254158/5379931.
However, I am getting errors still. If I set Access-Control-Allow-Origin like this:
res.header("Access-Control-Allow-Origin", "http://localhost:8100");
I get this error:
XMLHttpRequest cannot load URL. Response to preflight request doesn't pass
access control check: The 'Access-Control-Allow-Origin' header has a value
'http://localhost:8100/' that is not equal to the supplied origin. Origin
'http://localhost:8100' is therefore not allowed access.
If I set my Access-Control-Allow-Origin header like this:
res.header("Access-Control-Allow-Origin", "http://localhost:8100/");
I get this error:
XMLHttpRequest cannot load URL. No 'Access-Control-Allow-Origin' header is
present on the requested resource. Origin 'http://localhost:8100' is
therefore not allowed access. The response had HTTP status code 400.
Here is the rest of my express 4 code that is relevant:
router.use(function(req, res, next) {
res.header("Access-Control-Allow-Origin", "http://localhost:8100");
res.header("Access-Control-Allow-Headers", "Origin, Authorization, X-Requested-With, Content-Type, Accept");
res.header("Access-Control-Allow-Credentials", true);
res.header("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS");
next();
});
It looks like you forgot to respond to the options request. By not responding, it will go to your error handler and be dealt with as if it were an error.
Just send a 200 status within your .use if it is an options request so that it doesn't reach your error handler.
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 the No 'Access-Control-Allow-Origin'. I tried using node-http-proxy and Vhosts Apache but not having much succes, please see full error and code below.
XMLHttpRequest cannot load localhost:3000. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'localhost:8888' is therefore not allowed access."
// Api Using Node/Express
var express = require('express');
var app = express();
var contractors = [
{
"id": "1",
"name": "Joe Blogg",
"Weeks": 3,
"Photo": "1.png"
}
];
app.use(express.bodyParser());
app.get('/', function(req, res) {
res.json(contractors);
});
app.listen(process.env.PORT || 3000);
console.log('Server is running on Port 3000')
Angular code
angular.module('contractorsApp', [])
.controller('ContractorsCtrl', function($scope, $http,$routeParams) {
$http.get('localhost:3000').then(function(response) {
var data = response.data;
$scope.contractors = data;
})
HTML
<body ng-app="contractorsApp">
<div ng-controller="ContractorsCtrl">
<ul>
<li ng-repeat="person in contractors">{{person.name}}</li>
</ul>
</div>
</body>
Try adding the following middleware to your NodeJS/Express app (I have added some comments for your convenience):
// Add headers before the routes are defined
app.use(function (req, res, next) {
// Website you wish to allow to connect
res.setHeader('Access-Control-Allow-Origin', 'http://localhost:8888');
// Request methods you wish to allow
res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE');
// Request headers you wish to allow
res.setHeader('Access-Control-Allow-Headers', 'X-Requested-With,content-type');
// Set to true if you need the website to include cookies in the requests sent
// to the API (e.g. in case you use sessions)
res.setHeader('Access-Control-Allow-Credentials', true);
// Pass to next layer of middleware
next();
});
(You might need to use 127.0.0.1 instead of localhost.)
Accepted answer is fine, in case you prefer something shorter, you may use a plugin called cors available for Express.js.
It's simple to use, for this particular case:
var cors = require('cors');
// use it before all route definitions
app.use(cors({origin: 'http://localhost:8888'}));
(You might need to use 127.0.0.1 instead of localhost.)
The request origin needs to match the allowed origin(s), and you can also have multiple of them:
app.use(
cors({origin: ['http://localhost:8888', 'http://127.0.0.1:8888']})
);
Another way, is simply add the headers to your route:
router.get('/', function(req, res) {
res.setHeader('Access-Control-Allow-Origin', '*');
res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE'); // If needed
res.setHeader('Access-Control-Allow-Headers', 'X-Requested-With,content-type'); // If needed
res.setHeader('Access-Control-Allow-Credentials', true); // If needed
res.send('cors problem fixed:)');
});
The top answer worked fine for me, except that I needed to whitelist more than one domain.
Also, top answer suffers from the fact that OPTIONS request isn't handled by middleware and you don't get it automatically.
I store whitelisted domains as allowed_origins in Express configuration and put the correct domain according to origin header since Access-Control-Allow-Origin doesn't allow specifying more than one domain.
Here's what I ended up with:
var _ = require('underscore');
function allowCrossDomain(req, res, next) {
res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
var origin = req.headers.origin;
if (_.contains(app.get('allowed_origins'), origin)) {
res.setHeader('Access-Control-Allow-Origin', origin);
}
if (req.method === 'OPTIONS') {
res.send(200);
} else {
next();
}
}
app.configure(function () {
app.use(express.logger());
app.use(express.bodyParser());
app.use(allowCrossDomain);
});
The answer code allow only to localhost:8888. This code can't be deployed to the production, or different server and port name.
To get it working for all sources, use this instead:
// Add headers
app.use(function (req, res, next) {
// Website you wish to allow to connect
res.setHeader('Access-Control-Allow-Origin', '*');
// Request methods you wish to allow
res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, PATCH, DELETE');
// Request headers you wish to allow
res.setHeader('Access-Control-Allow-Headers', 'X-Requested-With,content-type');
// Set to true if you need the website to include cookies in the requests sent
// to the API (e.g. in case you use sessions)
res.setHeader('Access-Control-Allow-Credentials', true);
// Pass to next layer of middleware
next();
});
Install cors dependency in your project:
npm i --save cors
Add to your server configuration file the following:
var cors = require('cors');
app.use(cors());
It works for me with 2.8.4 cors version.
Hi this happens when the front end and backend is running on different ports. The browser blocks the responses from the backend due to the absence on CORS headers. The solution is to make add the CORS headers in the backend request. The easiest way is to use cors npm package.
var express = require('express')
var cors = require('cors')
var app = express()
app.use(cors())
This will enable CORS headers in all your request. For more information you can refer to cors documentation
https://www.npmjs.com/package/cors
This worked for me.
app.get('/', function (req, res) {
res.header("Access-Control-Allow-Origin", "*");
res.send('hello world')
})
You can change * to fit your needs. Hope this can help.
All the other answers didn't work for me. (including cors package, or setting headers through middleware)
For socket.io 3^ this worked without any extra packages.
const express = require('express');
const app = express();
const server = require('http').createServer(app);
const io = require('socket.io')(server, {
cors: {
origin: "*",
methods: ["GET", "POST"]
}
});
app.all('*', function(req, res,next) {
/**
* Response settings
* #type {Object}
*/
var responseSettings = {
"AccessControlAllowOrigin": req.headers.origin,
"AccessControlAllowHeaders": "Content-Type,X-CSRF-Token, X-Requested-With, Accept, Accept-Version, Content-Length, Content-MD5, Date, X-Api-Version, X-File-Name",
"AccessControlAllowMethods": "POST, GET, PUT, DELETE, OPTIONS",
"AccessControlAllowCredentials": true
};
/**
* Headers
*/
res.header("Access-Control-Allow-Credentials", responseSettings.AccessControlAllowCredentials);
res.header("Access-Control-Allow-Origin", responseSettings.AccessControlAllowOrigin);
res.header("Access-Control-Allow-Headers", (req.headers['access-control-request-headers']) ? req.headers['access-control-request-headers'] : "x-requested-with");
res.header("Access-Control-Allow-Methods", (req.headers['access-control-request-method']) ? req.headers['access-control-request-method'] : responseSettings.AccessControlAllowMethods);
if ('OPTIONS' == req.method) {
res.send(200);
}
else {
next();
}
});
Add following code in app.js of NODEJ Restful api to avoid "Access-Control-Allow-Origin" error in angular 6 or any other framework
var express = require('express');
var app = express();
var cors = require('cors');
var bodyParser = require('body-parser');
//enables cors
app.use(cors({
'allowedHeaders': ['sessionId', 'Content-Type'],
'exposedHeaders': ['sessionId'],
'origin': '*',
'methods': 'GET,HEAD,PUT,PATCH,POST,DELETE',
'preflightContinue': false
}));
You could use cors package to handle it.
var cors = require('cors')
var app = express()
app.use(cors())
for setting the specific origin
app.use(cors({origin: 'http://localhost:8080'}));
know more
You can use "$http.jsonp"
OR
Below is the work around for chrome for local testing
You need to open your chrome with following command. (Press window+R)
Chrome.exe --allow-file-access-from-files
Note : Your chrome must not be open. When you run this command chrome will open automatically.
If you are entering this command in command prompt then select your chrome installation directory then use this command.
Below script code for open chrome in MAC with "--allow-file-access-from-files"
set chromePath to POSIX path of "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome"
set switch to " --allow-file-access-from-files"
do shell script (quoted form of chromePath) & switch & " > /dev/null 2>&1 &"
second options
You can just use open(1) to add the flags: open -a 'Google Chrome' --args --allow-file-access-from-files
/**
* Allow cross origin to access our /public directory from any site.
* Make sure this header option is defined before defining of static path to /public directory
*/
expressApp.use('/public',function(req, res, next) {
res.setHeader("Access-Control-Allow-Origin", "*");
// Request headers you wish to allow
res.setHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
// Set to true if you need the website to include cookies in the requests sent
res.setHeader('Access-Control-Allow-Credentials', true);
// Pass to next layer of middleware
next();
});
/**
* Server is about set up. Now track for css/js/images request from the
* browser directly. Send static resources from "./public" directory.
*/
expressApp.use('/public', express.static(path.join(__dirname, 'public')));
If you want to set Access-Control-Allow-Origin to a specific static directory you can set the following.
Apart from all listed answers, I had the same error
I have both access to frontend and backend, I already added cors module app.use(cors()); Still, I was struggling with this error.
After some debugging, I found the issue. When I upload a media which size was more than 1 MB then the error was thrown by Nginx server
<html>
<head>
<title>413 Request Entity Too Large</title>
</head>
<body>
<center>
<h1>413 Request Entity Too Large</h1>
</center>
<hr>
<center>nginx/1.18.0</center>
</body>
</html>
But in the console of frontend, I found the error
Access to XMLHttpRequest at 'https://api.yourbackend.com' from origin 'https://web.yourfromntend.com' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
So It makes confusion here. But the route cause of this error was from nginx configuration. It's just because the directive client_max_body_size value has been set to 0 by default. It determines what the allowable HTTP request size can be is client_max_body_size. This directive may already be defined in your nginx.conf file located at /etc/nginx/nginx.conf Now you need to add/edit the value of the directive client_max_body_size either at http or server.
server {
client_max_body_size 100M;
...
}
Once you have set your desired value, save your changes and reload Nginx: service nginx reload
After these changes, It's working well
REFERENCE: https://www.keycdn.com/support/413-request-entity-too-large#:~:text=%23,processed%20by%20the%20web%20server.&text=An%20example%20request%2C%20that%20may,e.g.%20a%20large%20media%20file).
We'll see if the top 2 answers accept my edit, but it's very likely you're gonna have to either add or use 127.0.0.1 instead of localhost.
With the cors package, you're even able to use more than one allowed origin:
app.use(
cors({ origin: ["http://localhost:8888", "http://127.0.0.1:8888"] })
);
And you could use origin: "*" if you wish to allow for anything.
For more info, do check out Web Dev Simplified's tutorial.