Response to preflight request doesn't pass access control check

You are running into CORS issues.

There are several ways to fix/workaround this.

1. Turn off CORS. For example: how to turn off cors in chrome
2. Use a plugin for your browser
3. Use a proxy such as nginx. example of how to set up
4. 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.

More verbosely, you are trying to access api.serverurl.com from localhost. This is the exact definition of cross domain request.

By either turning it off just to get your work done (OK, but poor security for you if you visit other sites and just kicks the can down the road) you can use a proxy which makes your browser think all requests come from local host when really you have local server that then calls the remote server.

so api.serverurl.com might become localhost:8000/api and your local nginx or other proxy will send to the correct destination.

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Now by popular demand, 100% more CORS info....same great taste!

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Bypassing CORS is exactly what is shown for those simply learning the front end. https://codecraft.tv/courses/angular/http/http-with-promises/

My "API Server" is an PHP Application so to solve this problem I found the below solution to work:

Place the lines in index.php

header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, POST, PATCH, PUT, DELETE, OPTIONS');
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token');

In AspNetCore web api, this issue got fixed by adding "Microsoft.AspNetCore.Cors" (ver 1.1.1) and adding the below changes on Startup.cs.

public void ConfigureServices(IServiceCollection services)
{ 
    services.AddCors(options =>
    {
          options.AddPolicy("AllowAllHeaders",
                builder =>
            {
                    builder.AllowAnyOrigin()
                           .AllowAnyHeader()
                           .AllowAnyMethod();
                });
    });
    .
    .
    .
}

and

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{


    // Shows UseCors with named policy.
    app.UseCors("AllowAllHeaders");
    .
    .
    .
}

and putting [EnableCors("AllowAllHeaders")] on the controller.