Synopsis

This module allows setting arbitrary HTTP headers.

Examples

  expires       24h;
  expires       0;
  expires       -1;
  expires       epoch;
  add_header    Cache-Control  private;

Directives

add_header

syntax: add_header name value

default: none

context: http, server, location

Directive adds headers to the HTTP response when the response code is equal to 200, 204, 301, 302 or 304.

In the value it is possible to use variables.

Note that it just appends a new header entry to the output header list. So you can't use this directive to rewrite existing headers like Server. Use the headers_more module for it.

expires

syntax: expires [time|epoch|max|off]

default: expires off

context: http, server, location

It allows or prevents adding or changing the Expires and Cache-Control in the response headers.

It is possible to assign positive or negative times. Time in the Expires header is obtained as the sum of the current time and the time assigned in the directive.

epoch indicates the absolute time of 1 January, 1970, 00:00:01 GMT. max assigns the time of 31 December 2037 23:59:59 GMT to the Expires header and 10 years for the Cache-Control header.

Contents of the Cache-Control header depends on the sign of the preset time:

negative time: Cache-Control: no-cache
positive time or equal to zero: Cache-Control: max-age = #, where # is the time in seconds, assigned in the directive.

The parameter "off" prevents changes to "Expires" and "Cache-Control" in the headers.

Note: expires works only for 200, 204, 301, 302, and 304 responses.