Origin origin is not allowed by Access-Control-Allow-Origin

Question

XMLHttpRequest cannot load http   localhost 8080 api test  Origin http   localhost 3000 is not allowed by Access-Control-Allow-Origin     I read about cross domain ajax requests  and understand the underlying security issue  In my case  2 servers are running locally  and like to enable cross domain requests during testing   localhost 8080 - Google Appengine dev server localhost 3000 - Node js server   I am issuing an ajax request to localhost 8080 - GAE server while my page is loaded from node server  What is the easiest  and safest   Don t want to start chrome with disable-web-security option   If I have to change  Content-Type   should I do it at node server  How

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Hi This is the way to solve CORS problem in node Just add these lines on server  api  side in Node js or what ever your server File   befor that make sure to install  cors       const express   require  express        const app   express        app use express json         var cors   require  cors        app use cors

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You have to enable CORS to solve this if your app is created with simple node js set it in your response headers like var http   require  http     http createServer function  request  response    response writeHead 200         Content-Type    text plain        Access-Control-Allow-Origin              Access-Control-Allow-Methods    GET PUT POST DELETE      response end  Hello World n       listen 3000    if your app is created with express framework use a CORS middleware like var allowCrossDomain   function req  res  next        res header  Access-Control-Allow-Origin    quot   quot        res header  Access-Control-Allow-Methods    GET PUT POST DELETE        res header  Access-Control-Allow-Headers    Content-Type        next       and apply via app configure function         app use allowCrossDomain         some other code          Here are two reference links  how-to-allow-cors-in-express-nodejs diving-into-node-js-very-first-app  see the Ajax section

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use dataType   jsonp   works for me       async function get ajax data            var  reprojected lat lng   await   ajax                                    type   GET                                    dataType   jsonp                                    data                                       url   reprojection url                                   error  function  jqXHR  textStatus  errorThrown                                         console log jqXHR                                                                       success  function  data                                         console log data                                             note  data is already json type  you just specify dataType  jsonp                                      return data                                                                                 function

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router use function req  res  next    res header  Access-Control-Allow-Origin         res header  Access-Control-Allow-Methods         res header  Access-Control-Allow-Headers         next         add this to your routes which you are calling from front-end  Ex- if you call for http   localhost 3000 users register you must add this code fragment on your back-end  js file which this route lays

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Since they are running on different ports  they are different JavaScript origin   It doesn t matter that they are on the same machine hostname   You need to enable CORS on the server  localhost 8080    Check out this site  http   enable-cors org   All you need to do is add an HTTP header to the server   Access-Control-Allow-Origin  http   localhost 3000   Or  for simplicity   Access-Control-Allow-Origin      Thought don t use     if your server is trying to set cookie and you use withCredentials   true     when responding to a credentialed request  server must specify a domain  and cannot use wild carding    You can read more about withCredentials here

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If you are using express  you can use cors middleware as follows   var express   require  express   var cors   require  cors   var app   express    app use cors

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If you got 403 after that please reduce filters in WEB XML tomcat config to the following     lt filter gt     lt filter-name gt CorsFilter lt  filter-name gt     lt filter-class gt org apache catalina filters CorsFilter lt  filter-class gt     lt init-param gt       lt param-name gt cors allowed origins lt  param-name gt       lt param-value gt   lt  param-value gt     lt  init-param gt     lt init-param gt       lt param-name gt cors allowed methods lt  param-name gt       lt param-value gt GET POST HEAD OPTIONS PUT lt  param-value gt     lt  init-param gt     lt init-param gt       lt param-name gt cors allowed headers lt  param-name gt       lt param-value gt Content-Type X-Requested-With accept Origin Access-Control-Request-Method Access-Control-Request-Headers lt  param-value gt     lt  init-param gt     lt init-param gt       lt param-name gt cors exposed headers lt  param-name gt       lt param-value gt Access-Control-Allow-Origin Access-Control-Allow-Credentials lt  param-value gt     lt  init-param gt   lt  filter gt

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I was facing a problem while calling cross origin resource using ajax from chrome   I have used node js and local http server to deploy my node js app   I was getting error response  when I access cross origin resource  I found one solution on that    1  I have added below code to my app js file  res header  Access-Control-Allow-Origin         res header  Access-Control-Allow-Headers    X-Requested-With      2  In my html page called cross origin resource using   getJSON       getJSON  http   localhost 3000 users   function  data        alert         Success                 var response JSON stringify data       alert  success   response       document getElementById  employeeDetails   value response

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In router js just add code before calling get post methods  It works for me without errors     Importing modules  Brahmmeswar const express   require  express    const router   express Router     const Contact   require     models contacts     router use function req  res  next        res header  Access-Control-Allow-Origin             res header  Access-Control-Allow-Headers    Origin  X-Requested-With  Content-Type  Accept        next

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In case anyone searching for the solution   if you are using express here is the quick solution     const express   require  express   const cors   require  cors   const app   express     1  install cors using npm npm install cors --save  2  import it  require   const cors   require  cors    3  use it as middleware  app use cors     for details insatll and usage of cors   That is it  hopefully it works

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If you re in Google Chrome  try installing this add-on   https   chrome google com webstore detail allow-control-allow-origi nlfbmbojpeacfghkpbjhddihlkkiljbi related

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If you need a quick work around in Chrome for ajax requests  this chrome plugin automatically allows you to access any site from any source by adding the proper response header  Chrome Extension Allow-Control-Allow-Origin

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Add this to your NodeJS Server below imports   app use function req  res  next      res header  Access-Control-Allow-Origin           res header  Access-Control-Allow-Headers    Origin  X-Requested-With  Content-Type  Accept      next

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I finally got the answer for apache Tomcat8  You have to edit the tomcat web xml file   probabily it will be inside webapps folder    sudo gedit  opt tomcat webapps your directory WEB-INF web xml   find it and edit it   lt web-app gt     lt filter gt     lt filter-name gt CorsFilter lt  filter-name gt     lt filter-class gt org apache catalina filters CorsFilter lt  filter-class gt     lt init-param gt       lt param-name gt cors allowed origins lt  param-name gt       lt param-value gt   lt  param-value gt     lt  init-param gt     lt init-param gt       lt param-name gt cors allowed methods lt  param-name gt       lt param-value gt GET POST HEAD OPTIONS PUT lt  param-value gt     lt  init-param gt     lt init-param gt       lt param-name gt cors allowed headers lt  param-name gt       lt param-value gt Content-Type X-Requested-With accept Origin Access-Control-Request-Method Access-Control-Request-Headers lt  param-value gt     lt  init-param gt     lt init-param gt       lt param-name gt cors exposed headers lt  param-name gt       lt param-value gt Access-Control-Allow-Origin Access-Control-Allow-Credentials lt  param-value gt     lt  init-param gt     lt init-param gt       lt param-name gt cors support credentials lt  param-name gt       lt param-value gt true lt  param-value gt     lt  init-param gt     lt init-param gt       lt param-name gt cors preflight maxage lt  param-name gt       lt param-value gt 10 lt  param-value gt     lt  init-param gt   lt  filter gt     lt filter-mapping gt     lt filter-name gt CorsFilter lt  filter-name gt     lt url-pattern gt    lt  url-pattern gt   lt  filter-mapping gt      lt  web-app gt    This will allow Access-Control-Allow-Origin all hosts  If you need to change it from all hosts to only your host you can edit the   lt param-name gt cors allowed origins lt  param-name gt   lt param-value gt http   localhost 3000 lt  param-value gt    above code from   to your http   your public IP or http   www example com  you can refer here Tomcat filter documentation  Thanks

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For PHP  use this to set headers   header  Access-Control-Allow-Origin       header  Access-Control-Allow-Methods  PUT  GET  POST    header  Access-Control-Allow-Headers  Origin  X-Requested-With  Content-Type  Accept

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I accept  Rocket hazmat s answer as it lead me to the solution  It was indeed on the GAE server I needed to set the header  I had to set these   Access-Control-Allow-Origin  - gt       Access-Control-Allow-Headers  - gt   Origin  X-Requested-With  Content-Type  Accept    setting only  Access-Control-Allow-Origin   gave error  Request header field X-Requested-With is not allowed by Access-Control-Allow-Headers    Also  if auth token needs to be sent  add this too   Access-Control-Allow-Credentials  - gt   true    Also  at client  set withCredentials  this causes 2 requests to sent to the server  one with OPTIONS  Auth cookie is not send with it  hence need to treat outside auth

[javascript] Origin <origin> is not allowed by Access-Control-Allow-Origin

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