URL/Subdomain rewrites (htaccess)

Question

Say I have the following file:

http://www.example.com/images/folder/image.jpg

I want to serve it on

http://s1.example.com/folder/image.jpg

How can I do a htaccess rewrite to point it to it?

Like for example, I make a subdomain s1.example.com and then on that subdomain, I add a htaccess rule to point any files, to pull it from http://www.example.com/images/

Does serving files this way act as serving content from a cookieless domain?

Answer 1

First let me talk a bit about the concept of cookieless domains. Normally, when requesting anything over http, any relevant cookies are sent with the request. Cookies, are dependent on which domain they come from. The idea of using a cookieless domain is that you relocate static content that doesn't cookies, like images, to a separate domain so that no cookies will be sent with that request. This cuts out a small amount of traffic.

How much you gain from doing this depends on the type of page. The more images you have, the more you gain. If your site loads a big bunch of small images, such as avatars or image thumbnails, you might have a lot to gain. On the contrary, if your site doesn't use any cookies, you have nothing to gain. It's entirely possible that your page won't load noticeably faster, if it only uses a small amount of images, which will be cached between page loads anyway.

One thing to keep in mind, too, is that cookies set for example.com will also be sent with requests to s1.example.com as "s1." is a subdomain to example.com. You need to use www. (or any other subdomain of your choice) in order to separate the cookie spaces.

Secondly, if you decide that a cookieless domain is actually something worth trying, let's talk about the implementation.

Shikhar's solution is bad! While the solution appears to work on the surface, it actually defeats the purpose of using a cookieless domain. For every image, first the s1. url is tried. The s1. URL then makes a redirect to the www. domain which triggers a second http request. This is a loss, no matter how you look at it. What you need is a rewrite, which changes the URL internally on the web server, without the browser even realizing.

For simplicity, I'm assuming that all domains point to the same directory, so that www.example.com/something = example.com/something = s1.example.com/something = blub.example.com/something. This makes things simpler if you really need store the images physically in "www.example.com/images".

I'd recommend a .htaccess that looks a little something like this:

# Turn on rewrites
RewriteEngine On

# Rewrite all requests for images from s1, so they are fetched from the right place
RewriteCond %{HTTP_HOST} ^s1\.example\.com
# Prevent an endless loop from ever happening
RewriteCond %{REQUEST_URI} !^/images
RewriteRule (.+) /images/$1 [L]

# Redirect http://s1.example.com/ to the main page (in case a user tries it)
RewriteCond %{HTTP_HOST} ^s1\.example\.com
RewriteRule ^$ http://www.example.com/ [R=301,L]

# Redirect all requests with other subdomains, or without a subdomain to www.
# Eg, blub.example.com/something -> www.example.com/something
#     example.com/something      -> www.example.com/something
RewriteCond %{HTTP_HOST} !^www\.example\.com
RewriteCond %{HTTP_HOST} !^s1\.example\.com
RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L]

# Place any additional rewrites below.