I have the following shell script for a very simple HTTP server:

#!/bin/sh

echo "Serving at http://localhost:3000"
python -m SimpleHTTPServer 3000

I was wondering how I can enable or add a CORS header like Access-Control-Allow-Origin: * to this server?

Unfortunately, the simple HTTP server is really that simple that it does not allow any customization, especially not for the headers it sends. You can however create a simple HTTP server yourself, using most of SimpleHTTPRequestHandler, and just add that desired header.

For that, simply create a file simple-cors-http-server.py (or whatever) and, depending on the Python version you are using, put one of the following codes inside.

Then you can do python simple-cors-http-server.py and it will launch your modified server which will set the CORS header for every response.

With the shebang at the top, make the file executable and put it into your PATH, and you can just run it using simple-cors-http-server.py too.

Python 3 solution

Python 3 uses SimpleHTTPRequestHandler and HTTPServer from the http.server module to run the server:

#!/usr/bin/env python3
from http.server import HTTPServer, SimpleHTTPRequestHandler, test
import sys

class CORSRequestHandler (SimpleHTTPRequestHandler):
    def end_headers (self):
        self.send_header('Access-Control-Allow-Origin', '*')
        SimpleHTTPRequestHandler.end_headers(self)

if __name__ == '__main__':
    test(CORSRequestHandler, HTTPServer, port=int(sys.argv[1]) if len(sys.argv) > 1 else 8000)

Python 2 solution

Python 2 uses SimpleHTTPServer.SimpleHTTPRequestHandler and the BaseHTTPServer module to run the server.

#!/usr/bin/env python2
from SimpleHTTPServer import SimpleHTTPRequestHandler
import BaseHTTPServer

class CORSRequestHandler (SimpleHTTPRequestHandler):
    def end_headers (self):
        self.send_header('Access-Control-Allow-Origin', '*')
        SimpleHTTPRequestHandler.end_headers(self)

if __name__ == '__main__':
    BaseHTTPServer.test(CORSRequestHandler, BaseHTTPServer.HTTPServer)

Python 2 & 3 solution

If you need compatibility for both Python 3 and Python 2, you could use this polyglot script that works in both versions. It first tries to import from the Python 3 locations, and otherwise falls back to Python 2:

#!/usr/bin/env python
try:
    # Python 3
    from http.server import HTTPServer, SimpleHTTPRequestHandler, test as test_orig
    import sys
    def test (*args):
        test_orig(*args, port=int(sys.argv[1]) if len(sys.argv) > 1 else 8000)
except ImportError: # Python 2
    from BaseHTTPServer import HTTPServer, test
    from SimpleHTTPServer import SimpleHTTPRequestHandler

class CORSRequestHandler (SimpleHTTPRequestHandler):
    def end_headers (self):
        self.send_header('Access-Control-Allow-Origin', '*')
        SimpleHTTPRequestHandler.end_headers(self)

if __name__ == '__main__':
    test(CORSRequestHandler, HTTPServer)

Try an alternative like http-server

As SimpleHTTPServer is not really the kind of server you deploy to production, I’m assuming here that you don’t care that much about which tool you use as long as it does the job of exposing your files at http://localhost:3000 with CORS headers in a simple command line

# install (it requires nodejs/npm)
npm install http-server -g

#run
http-server -p 3000 --cors

Need HTTPS?

If you need https in local you can also try caddy or certbot

Some related tools you might find useful

• ngrok: when running ngrok http 3000, it creates an url https://$random.ngrok.com that permits anyone to access your http://localhost:3000 server. It can expose to the world what runs locally on your computer (including local backends/apis)

• localtunnel: almost the same as ngrok

• now: when running now, it uploads your static assets online and deploy them to https://$random.now.sh. They remain online forever unless you decide otherwise. Deployment is fast (except the first one) thanks to diffing. Now is suitable for production frontend/SPA code deployment It can also deploy Docker and NodeJS apps. It is not really free, but they have a free plan.

I had the same problem and came to this solution:

class Handler(SimpleHTTPRequestHandler):
    def send_response(self, *args, **kwargs):
        SimpleHTTPRequestHandler.send_response(self, *args, **kwargs)
        self.send_header('Access-Control-Allow-Origin', '*')

I simply created a new class inheriting from SimpleHTTPRequestHandler that only changes the send_response method.

You’ll need to provide your own instances of do_GET() (and do_HEAD() if choose to support HEAD operations). something like this:

class MyHTTPServer(SimpleHTTPServer):

    allowed_hosts = (('127.0.0.1', 80),)

    def do_GET(self):
        if self.client_address not in allowed_hosts:
            self.send_response(401, 'request not allowed')
        else:
            super(MyHTTPServer, self).do_Get()