http_headers module

Allows adding the “Expires” and “Cache-Control” header fields, and arbitrary fields, to a response header.

Example Configuration

expires    24h;
expires    modified +24h;
expires    @24h;
expires    0;
expires    -1;
expires    epoch;
expires    $expires;
add_header Cache-Control private;

Directives

add_header

Syntax:

add_header name value [always];

Default:

—

Context:

http, server, location, if in location

Adds the specified field to a response header provided that the response code equals 200, 201, 204, 206, 301, 302, 303, 304, 307, or 308. Parameter value can contain variables.

There could be several add_header directives. These directives are inherited from the previous configuration level if and only if there are no add_header directives defined on the current level.

If the always parameter is specified, the header field will be added regardless of the response code.

add_trailer

Syntax:

add_trailer name value [always];

Default:

—

Context:

http, server, location, if in location

Adds the specified field to the end of a response provided that the response code equals 200, 201, 206, 301, 302, 303, 307, or 308. Parameter value can contain variables.

There could be several add_trailer directives. These directives are inherited from the previous configuration level if and only if there are no add_trailer directives defined on the current level.

If the always parameter is specified the specified field will be added regardless of the response code.

expires

Syntax:

expires [modified] time;
expires epoch | max | off;

Default:

expires off;

Context:

http, server, location, if in location

Enables or disables adding or modifying the “Expires” and “Cache-Control” response header fields provided that the response code equals 200, 201, 204, 206, 301, 302, 303, 304, 307, or 308. The parameter can be a positive or negative time.

The time in the “Expires” field is computed as a sum of the current time and time specified in the directive. If the modified parameter is used then the time is computed as a sum of the file’s modification time and the time specified in the directive.

In addition, it is possible to specify a time of day using the “@” prefix:

expires @15h30m;

The contents of the “Cache-Control” field depends on the sign of the specified time:

• time is negative — “Cache-Control: no-cache”.

• time is positive or zero — “Cache-Control: max-age=`t`”, where t is a time specified in the directive, in seconds.

epoch	sets “Expires” to the value “Thu, 01 Jan 1970 00:00:01 GMT”, and “Cache-Control” to “no-cache”.
max	sets “Expires” to the value “Thu, 31 Dec 2037 23:55:55 GMT”, and “Cache-Control” to 10 years.
off	disables adding or modifying the “Expires” and “Cache-Control” response header fields.

The last parameter value can contain variables:

map $sent_http_content_type $expires {
    default         off;
    application/pdf 42d;
    ~image/         max;
}

expires $expires;