NGINX is a popular web server and reverse proxy server that is commonly used to serve and manage web applications. One of its capabilities is to perform URL redirection using the proxy_redirect directive, which is used to modify the URL in the response headers when NGINX acts as a reverse proxy.

The proxy_redirect directive is used to adjust the URLs in HTTP Location and Refresh headers returned by a proxied server. It’s particularly useful when you are using NGINX as a reverse proxy to redirect requests from one server to another, and you want to ensure that the URLs in the response headers are correctly adjusted to match the new server.

The basic syntax of the proxy_redirect directive is as follows:

proxy_redirect [default | off | redirect_regex | redirect replacement];

Here’s a breakdown of the options:

• default: This option performs a standard replacement of the server name or IP address in the response headers. It assumes that the backend server you are proxying to is located at the same path as the frontend server.
• off: Disables URL redirection.
• redirect_regex: Allows you to use regular expressions to define the replacement.
• redirect: This is used to specify a specific replacement pattern. The replacement pattern can include variables that refer to parts of the original request.

Here’s an example of how you might use proxy_redirect in an NGINX configuration:

location /old {
    proxy_pass http://backend_server;
    proxy_redirect default; # This is the default setting
}

In this example, when a request is made to /old on the NGINX server, it’s reverse proxied to the backend_server. The proxy_redirect default; line ensures that any redirections provided by the backend_server in response headers are adjusted to match the frontend server’s URL structure.

Keep in mind that configuring proxy_redirect correctly is important to ensure that URLs in response headers are accurately adjusted. The specific configuration you need depends on your use case and the structure of your application.

Additionally, starting with NGINX version 1.15.9, the proxy_redirect directive can also be used in conjunction with regular expressions for more advanced redirection scenarios.

Remember to test your configuration thoroughly to make sure that the URL redirections are working as expected.