David Walsh Blog

Prevent JavaScript Hotlinking with .htaccess

Almost a decade (!) ago I wrote a post about preventing image hotlinking.  We all have the right to protect imagery hosted on our domain because it can slow our site down tremendously.  I love that post because it shows you how to replace the image requested with any image of your choosing; for example, I could replace any incoming image request with my logo:


<IfModule mod_rewrite.c>
  RewriteEngine on
  RewriteCond %{HTTP_REFERER} !^$
  RewriteCond %{HTTP_REFERER} !^https://davidwalsh.name/.*$ [NC]
  RewriteRule .*.(png|gif|jpe?g)$ [F,NC]
</IfModule>

But what should we do when someone is hotlinking JavaScript files?  I’ve written a ton about JavaScript over the years, oftentimes providing a demo page, so you can probably guess I host many JavaScript files, including all of my MooTools plugin files.  I’ve chosen a somewhat harsh approach to prevent hotlinking of JavaScript files:


<IfModule mod_rewrite.c>
  RewriteEngine on
  RewriteCond %{HTTP_REFERER} !^$
  RewriteCond %{HTTP_REFERER} !^https://davidwalsh.name/.*$ [NC]
  RewriteRule \.(js)$ http://davidwalsh.name/hotlink.js [R,L]
</IfModule>

The snippet above, placed in my .htaccess file, directs my server to ignore the JavaScript file the foreign domain has requested and instead provide a hotlink.js file whose contents are a bit devious:


window.location = 'https://davidwalsh.name/';

A bit harsh?  Perhaps, but my server is put under undue stress, they shouldn’t be hotlinking files, and being redirected to my site is a good indication of where they should be looking to fix the issue.  I could do worse, like serve evil.js or redirect them to an adult site, but I’d prefer not to go that far.

Protect your server from hotlinking — you have every right to and, in the end, you’re probably doing them a favor.