3.15. Expirations
Apache Version 1.2 brought the expires module, mod_expires, into the main distribution. The point of this module is to allow the webmaster to set the returned headers to pass information to clients' browsers about documents that will need to be reloaded because they are apt to change, or alternatively, that are not going to change for a long time and can therefore be cached. There are three directives.
3.15.1. ExpiresActive
ExpiresActive [on|off] Anywhere, .htaccess when AllowOverride Indexes
ExpiresActive simply switches the expiration mechanism on and off.
3.15.2. ExpiresByType
ExpiresByType mime-type time Anywhere, .htaccess when AllowOverride Indexes
ExpiresByType takes two arguments. mime-type specifies a MIME type of file; time specifies how long these files are to remain active. There are two versions of the syntax. The first is:
code seconds
There is no space between code and seconds. code is one of the following:
- A
Access time (or now, in other words)
- M
Last modification time of the file
seconds is simply a number. For example:
A565656
specifies 565656 seconds after the access time.
The more readable second format is:
base [plus] number type [number type ...]
where base is one of the following:
- access
Access time
- now
Synonym for access
- modification
Last modification time of the file
The plus keyword is optional, and type is one of the following:
years
months
weeks
days
hours
minutes
seconds
For example:
now plus 1 day 4 hours
does what it says.
3.15.3. ExpiresDefault
ExpiresDefault time Anywhere, .htaccess when AllowOverride Indexes
This directive sets the default expiration time, which is used when expiration is enabled but the file type is not matched by an ExpireByType directive.
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