Changing content on-the-fly

Sometimes, it may be helpful to postprocess what comes from your application. Maybe you would like to add a string at a certain point in your page to show which frontend server delivered that page to the client. Or maybe you would like to perform a transformation on the rendered HTML page. NGINX provides three modules that could be useful here: the addition module, the sub module, and the xslt module.

Using the addition module

The addition module works as a filter to add text before and/or after a response. It is not compiled by default, so if you want to make use of this feature, you must enable it at configure time by adding --with-http_addition_module.

This filter works by referencing a subrequest, which is then either appended to a request, or placed at the beginning of one:

server {

  root /home/www;

  location / {

    add_before_body /header;

    add_after_body /footer;

  }

  location /header {

    proxy_pass http://127.0.0.1:8080/header;

  }

  location...