Comment systems

Vuukle

Vuukle is an audience engagement and commenting platform.

Giscus

Giscus is a comment system powered by GitHub Discussions.

Disqus

Disqus is a worldwide blog comment hosting service for web sites and online communities that use a networked platform.

Livefyre

Livefyre is a platform that integrates with the social web to boost social interaction.

ReplyBox

ReplyBox is a privacy-focused comment system designed to collect, store, and display user feedback while minimizing data exposure and supporting secure interaction.

IntenseDebate

IntenseDebate is a blog commenting system that supports Typepad, Blogger and Wordpress blogs. The system allows blog owners to track and moderate comments from one place with features like threading, comment analytics, user reputation, and comment aggregation.

Isso is a lightweight commenting server written in Python and JavaScript, referred to as "Ich schrei sonst" in German.

Annoto

Annoto is a platform that transforms video viewing into an interactive, social, and collaborative experience rather than a passive individual activity.

Twikoo

Twikoo is a simple, safe, free comment system.

utterances

Utterances is a lightweight comments widget built on GitHub issues.

Cackle

Cackle is a cloud services platform for increasing conversion using comments, feedback collection, online consultant and surveys.

Commento

Commento is a tool for fostering discussion and improving engagement on websites.

Cove

Cove is a commenting and community platform that integrates with Ghost sites to enable reader discussions and user engagement.

Question2Answer

Question2Answer (Q2A) is a popular open-source Q&A platform for PHP/MySQL.