To improve the site performance, I'm adding following http headers in IIS 7.5.
Expires: Sun, 29 Mar 2020 00:00:00 GMT and
Cache-Control:Public
I'm adding these headers for images folder in site's virtual directory.
When I access the site, I see that for each image present in this folder; those response headers were:
Accept-Ranges:bytes
Cache-Control:no-cache, no-store,Public
Content-Length:4445
Content-Type:image/png
Date:Fri, 06 Jun 2014 09:18:36 GMT
ETag:"16874c2af55ecf1:0"
Expires:-1,Sun, 29 Mar 2020 00:00:00 GMT
Last-Modified:Wed, 23 Apr 2014 13:08:48 GMT
max-age:604800
Pragma:no-cache
Server:Microsoft-IIS/7.5
X-Powered-By:ASP.NET
I need browser to take these images from it's cache instead of requesting again from server. How should I achieve it?
Your header shows that you add a new value but you need to replace the existing one
Cache-Control:no-cache, no-store,Public
Expires:-1,Sun, 29 Mar 2020 00:00:00 GMT
no-cache, no-store stands for no cache and -1 says that the content is already expired.
Instead of doing it from the code you can easily set it in the root web.config file as
...
<location path="images">
<system.webServer>
<staticContent>
<clientCache cacheControlMode="UseExpires"
httpExpires="Sun, 29 Mar 2020 00:00:00 GMT" />
</staticContent>
</system.webServer>
</location>
</configuration>
where images is a name of your directory
or add dedicated web.config file directly in the target directory
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<staticContent>
<clientCache cacheControlMode="UseExpires"
httpExpires="Sun, 29 Mar 2020 00:00:00 GMT" />
</staticContent>
</system.webServer>
</configuration>
You can also use cacheControlMode="UseMaxAge" and set specific time of expiration
Example to set expiration in 7 days
<clientCache cacheControlMode="UseMaxAge"
cacheControlMaxAge="7.00:00:00" />
Read more http://msdn.microsoft.com/en-us/library/ms689443.aspx
