Access To Fetch At From Origin 'http://localhost:3000' Has Been Blocked By Cors Policy

Adding to the database shows the error. what should I do? Access to fetch at 'http:xxx' from origin 'http://localhost:3000' has been blocked by CORS policy: Response to preflight

Solution 1:

try using ''no-cors' mode.

fetch('http://localhost:8080/example', {
            mode: 'no-cors',
            method: "post",
            headers: {
                 "Content-Type": "application/json"
            },
            body: JSON.stringify(ob)
 })

Solution 2:

Your server should respond with a response that looks like below

Access-Control-Allow-Origin: https://localhost:3000

Untill you are able to configure that as a workaround you can install the below chrome extension to resume your testing

https://chrome.google.com/webstore/detail/who-cors/hnlimanpjeeomjnpdglldcnpkppmndbp?hl=en-GB

But the above is only a workaround to continue development

I would suggest you read this article for understanding CORS https://javascript.info/fetch-crossorigin

Solution 3:

For browser CORS is enabled by default and you need to tell the Browser it's ok for send a request to server that not served your client-side app ( static files ).

if you use RestFul API with node and express add this middleware to your file

app.use((req, res, next) => {
  res.header("Access-Control-Allow-Origin", "*")
}) 

Solution 4:

The middleware should be like this.

app.use((req, res, next) => {
  res.header({"Access-Control-Allow-Origin": "*"});
  next();
}) 

Solution 5:

I resolved the issue by installing the cors node module and adding this on the requested server

const cors = require("cors");
app.use(cors());