Public IP Address API with two lines of Nginx config

Here is how I set up a "show my public IP address" with Nginx without any backend (no PHP, no Nginx-Lua, ...).

The following block does the trick:

location /ip {
    default_type text/plain;
    return 200 $remote_addr;

The response is simply the IP address of the client:

$ curl

The default_type text/plain directive has no utility other than preventing Web browsers from attempting to download the response as a file. That is, a Web browser can display the IP address directly.
For programs interacting with the endpoint, it has no particular utility.

Bonus: JSON response

Want a JSON response? Sure, it is perfectly doable:

location /json_ip {
    default_type application/json;
    return 200 "{\"ip\":\"$remote_addr\"}";

The response is now a pretty JSON document:

$ curl -s | jq
    "ip": "2001:1b48:103::189"

I hope that little Nginx trick will save you some maintenance time.