I made a contact form that sends the data URL encoded if JS is disabled, or JSON if JS is enabled. If the back end gets url-encoded data, it's spam. I also use

I made a contact form that sends the data URL encoded if JS is disabled, or JSON if JS is enabled. If the back end gets url-encoded data, it's spam. I also use the hidden field trick, but I label it phone number and fill it with zeros. Then I hide it with an external stylesheet. I don't actually want a phone field, its a decoy. If it is changed from zeros, it is spam. Most spam bots don't seem to parse external stylesheets. I've had zero contact form spam with this method. Mind you it is a very low volume site. I was just having fun with it, making a php-style contact form backend but using node.js. I read lots of those old blog posts you mention.