These range from super easy stuff like checking for CHANGELOG.txt to checking the source for a reference to “drupal.css” (Drupal 4.7) to checking for common paths like taxonomy/term/1, and /user, (which might be aliased to something else with something like Pathauto/Path Redirect module), and so on.
However, since Drupal 4.6, there’s a super geeky trick you can use to fingerprint a Drupal site that works 90% of the time.
Get the Live HTTP Headers extension.
After restarting Firefox, click Tools > Live HTTP Headers. This’ll pop up a little window to the side.
Visit a website you suspect of being Drupalish. You know, like http://drupal.org/ (except, you know, I bet they’re running WordPress…).
Highlight the Live HTTP headers window and type “exp”, looking for the following in the output:
Expires: Sun, 19 Nov 1978 05:00:00 GMT
You know, like so!
Update 2008-May-31 Or! For you command-line junkies out there, check out TBarregren’s helpful bash script which allows you to just do ./is-drupal www.lullabot.com – Awesome!
By the way, this date has special significance in the Drupal community. Anyone know why? Eye-wink
Hat tip to chx for this trick. Smiling