In a previous post I explained how to create a .htaccess file to stop remote image linking (hotlinking) and bandwidth theft – however, there are some situations where you might want your image files linked to from remote sites – how do you make exceptions for these sites?

The code to block all sites from hotlinking to your images is, as follows (see my previous post for a detailed explanation of the code):
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?tomrafteryit.net [NC]
RewriteRule \.(png|gif|jpe?g)$ - [NC,F]

To allow Google, AltaVista, Gigablast, Comet Systems, and SearchHippo translators and caches to be able to link to images we need to use the following code:
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?tomrafteryit\.net [NC]
RewriteCond %{HTTP_REFERER} !^http://216\.239\.(3[2-9]|[45][0-9]|6[0-3]).*(www\.)?tomrafteryit\.net [NC]
RewriteCond %{HTTP_REFERER} !^http://babel.altavista.com/.*(www\.)?tomrafteryit\.net [NC]
RewriteCond %{HTTP_REFERER} !^http://216\.243\.113\.1/cgi/
RewriteCond %{HTTP_REFERER} !^http://search.*\.cometsystems\.com/search.*(www\.)?tomrafteryit\.net [NC]
RewriteCond %{HTTP_REFERER} !^http://.*searchhippo\.com.*(www\.)?tomrafteryit\.net [NC]
RewriteRule \.(png|gif|jpe?g)$ - [NC,F]

And obviously, everywhere you see my domain (tomrafteryit.net) in the code, substitute in your own domain.

In my last post on using .htaccess to block direct linking of images, I advised simply using the RewriteRule to forbid display of images (i.e. RewriteRule .(gif|png|jpg|jpeg?)$ – [NC,F]). This is a nice simple rule which works a treat to block display of your images on remote sites.

However, if you want to take this a step further, you can re-direct requests for images from remote webpages to an image of choice on your website. I have created an image, called stolenimage.jpg, which simply says “This image is stolen”. Anyone trying to link directly to images on my site is, therefore, inadvertantly serving that image on their pages.

The code to put in .htaccess to achieve this is:

RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?tomrafteryit.net [NC]
RewriteRule \.(png|gif|jpe?g)$ stolenimage.$1 [NC,L]

This is the same code as is in my previous post except for the RewriteRule.

It is a very good idea not to redirect a browser from one file type to another. The cleanest approach is to make a seperate version of your the stolenimage.jpg file in each format that you use on your site – for example I have one in gif format, one in jpg format, one in jpeg format, and one in png format. Then redirect each hot-linked image to the matching filetype.

In the RewriteRule above, the “$1” in the last line refers back to the contents of the parenthesis in the same line. That is, a request for a .jpg file will be redirected to http://www.tomrafteryit.net/stolenimage.jpg, and a request for a .gif file will be redirected to http://www.tomrafteryit.net/stolenimage.gif, etc.

The L in the square brackets is the “last rule” – it stops the rewriting process here and tells the .htaccess file not to apply any more rewriting rules. See the Apache mod_rewrite URL Rewriting Engine page for more.

Obviously, if you are feeling a bit mischievous, you can serve other images to people hotlinking your images – “Free shipping worldwide – we ship anywhere for free”, “Order one, get three free” or “This site supports the Taliban’s policy on Feminism” are some possibilities! You are only limited by your imagination.

Many thanks to all the contributers to the WebmasterWorld forums, from where I gleaned most of the information in these posts.