Spam filter for web forms

Sblam! is a web service that blocks spammy posts in blog comments, forums and guestbooks (blocks bots posting adverts for viagra, porn, credit, casinos, etc.). It detects spam server-side and doesn't bother users with any puzzles to retype.


  • It's installed on thousands of websites. Spammers caught on any one of them are blocked on all of them.
  • Combines several different anti-spam techniques, which gives it very high accuracy.
  • Filtering is transparent to the users. Works with all browsers and it's accessible to visually impaired users.
  • Allows you to decide what to do with suspected spam: you can block it, moderate it or ask the user to try again.
  • It has a database of several millions of words, phrases, links and IP addresses feeding an auto-learning bayesian classifier.
  • Checks links and senders in external blacklists such as Project Honeypot and LinkSleeve, taking into account dynamic IPs and public proxy servers.
  • Supports Unicode text semantics. Won't be fooled by special characters or CJK text.
  • Uses custom efficient non-XML API with on-the-fly compression and integrity checking.
  • Tweaked for spams typical on Polish pages, but supports English as well and should perform well regardless of language used.

Download and install Sblam!


How does it work?

A script installed on your site relays posts to the central Sblam! server for analysis and gives you the result.

What if filter mistakes legitimate comment for spam?

It's up to you how spams are handled. Sblam! has very high accuracy (typically 99.8%) and reports when it's not certain about the result, so you can manually moderate the toughest cases.

Does it work with WordPress, phpBB or <any other system>?

Yes. It does work with any PHP-based site which uses standard POST forms, but you have to integrate the filter yourself.

Is Sblam! completely free?

Yes, but please donate to help cover hosting costs.

Does Sblam! respect privacy?

Sblam! is intended only for posts that are going to be displayed publicly on the Internet. Please do not use it for private corespondence. Posts sent to Sblam! server are stored and their aggregated data (such as spammy links and IP blacklist) may be published.

Cookies (except a single one which is private to Sblam!) are not sent. You can keep some form fields secret by unsetting them with unset($_POST['secretfield']).


  1. Sblam! can be used freely, even on commercial websites.
  2. Privacy is not guaranteed. Posts will be stored and analyzed in order to improve quality of filtering.
  3. Accuracy of filtering is not guaranteed.
  4. Availability of the service is not guaranteed (the service has been running with little downtime since 2007).