Accessing a Client IP Address

You might want to collect some information about the clients accessing your app, like their IP address, which can be useful for analytics or security purposes. However, you might have noticed that when you directly try to access the IP address in your app, you receive or an undefined response due to technical limitations.

Fortunately, there is a workaround that you can use to access the client’s IP address. This is by using the CF-Connecting-IP header, which is available when using Cloudflare as the DNS provider for your custom domain, with Cloudflare Proxy enabled. Cloudflare is a content delivery network (CDN) that acts as an intermediary between your website and your visitors, improving the speed and security of your site.

Once you’ve added your domain to Cloudflare, follow these steps:

  1. Log-in to Space, click on the three dots (…) at the bottom right of your app’s icon on the Horizon and select Settings to open your app’s settings.
  2. Click Add Custom Domain (in the Domains tab for released apps) and enter your domain name (e.g.
  3. Go to the DNS settings in your Cloudflare Dashboard and add the required records. Make sure that Cloudflare Proxy is enabled when adding the A record.

Make sure to change your SSL/TLS encryption mode to Full in the Cloudflare Dashboard before doing this to avoid any unexpected issues.

  1. Verify that your domain has been added. Now, you can use the CF-Connecting-IP header to determine your client’s IP address when your app is accessed via the custom domain.

Here’s an example of how to access the header in ExpressJS:

app.get("/endpoint", (req, res) => {
const ipAddress = req.get("CF-Connecting-IP");
res.send(`Your IP address is ${ipAddress}`);

It’s important to note that the CF-Connecting-IP header can be spoofed, so you should always use additional security measures in conjunction with it.