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Get the IP address of a visitor in Flask

Get the IP address of a visitor in Flask

David Y.

—

The Problem

How do I get the IP address of a visitor in Flask?

The Solution

The IP address associated with the current request is stored in the Flask Request object’s remote_addr attribute. The following simple application will display the IP address of visitors to the /whatsmyip route:

Click to Copy
from flask import Flask, request

app = Flask(__name__)

@app.route("/whatsmyip", methods=["GET"])
def whats_my_ip():
    return request.remote_addr

app.run()

However, this will only work if users connect directly to your Flask web server. If it’s running behind a proxy such as NGINX, as is often the case in production environments, remote_addr will always be the local loopback address, 127.0.0.1. From Flask’s perspective, all requests are coming from the proxy.

Fortunately, we can fix this by including some additional code to tell Flask it is behind a proxy. This code will configure our application to assign request.remote_addr from the request’s X-Forwarded-For HTTP header.

Click to Copy
from werkzeug.middleware.proxy_fix import ProxyFix

app.wsgi_app = ProxyFix(
    app.wsgi_app, x_for=1, x_proto=1, x_host=1, x_prefix=1
)

ProxyFix must be called with the exact number of proxies that are in front of the Flask server, or malicious users will be able to spoof their IP addresses by including their own X-Forwarded-For header in their requests.

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