How Mollom works

An overview of how Mollom works

Mollom is a web service that analyzes the quality of content posted to websites. This includes comments, contact-form messages, blogs, forum posts, etc. Mollom specifically tries to determine whether this content is unwanted - i.e. "spam" - or desirable - i.e. "ham." Websites that allow visitors to contribute or post comments are constantly being flooded with inappropriate, distracting or even illegal commercial messages, many of which are uploaded by automatic "spambots." Mollom screens all contributions before they are posted to participating websites.

Websites using Mollom send data they want checked to, and Mollom replies with either a spam or ham classification. If Mollom is not certain, it will return an "unsure," typically prompting websites to ask Mollom's CAPTCHA server for an audio or visual CAPTCHA challenge to present to the user.

An overview of how Mollom works

Thanks to the "unsure" reply and the CAPTCHA challenges, Mollom avoids incorrectly classifying legitimate contributions as spam. The strategy of combining text classification with occasional CAPTCHAs has two important benefits:

  1. It effectively eliminates the need to moderate messages that Mollom decides to block since they are unlikely to have come from legitimate users.
  2. Because CAPTCHA rarely challenges legitimate content (currently only approximately 2% of human users are challenged with a CAPTCHA), it makes your site a lot more accessible while still greatly improving its overall quality.

One of Mollom's key features is that all participating sites can report comment spam that slipped through the cracks. Mollom combines and correlates this information and learns from it to help prevent future abuse.

You want to get started?

Now you know how Mollom works, you should be ready to start using Mollom on your website:

  1. Download a plugin for your website
  2. Create an account on
  3. Activate your website (requires authentication)

Get started

Want to learn more?

If you want to know more, we recommend that you check out our technical whitepaper or that you read the Mollom API documentation.