How To Prevent Image Copying

Chapter 4: Checking The Referring Page

• If you use an anti-leech script to prevent hot-linking, it works great:
  
  For example, imagine that 90% of users' browsers fill out the Referring Page correctly, but 10% don't:
  
  
  • If you install anti-leech script on your site, you can configure the script to allow browsers with both valid Referring Pages and blank Referring Pages, to see your images. In which case, all users will be able to see the images on your site.
    
    
  • However, if some other webmaster hot-links to your images, 90% of his users (with invalid Referring Pages) will not be able to see your images, and only 10% will.
  
  
• If you use an anti-leech script to prevent copying, it isn't nearly so good.
  
  For example, imagine that 90% of users' browsers fill out the Referring Page correctly, but 10% don't:
  
  
  • When the image "thief" wants to retrieve images from your site, he will probably simply type in the images' URLs. In this case the Referring Page from the browser is normally blank, thus to prevent it you'll have to ban access to images from browsers with blank Referring pages.
    
    
  • An unwanted side effect of banning access from browsers with blank Referring pages, is that you also have banned 10% of your "legitimate" users from seeing your images. Ouch!
    
    
  • In any case, it is possible for a determined image "thief" to use a browser which spoofs a valid Referring Page, and thus copy your images. So at the end of the day, you haven't really protected your images, but you have stopped many "legitimate" users from accessing your site!