Zulip has the best user experience of all the chat apps I’ve tried. With the discussion organized by topic within each channel, Zulip is the only app that makes hundreds of conversations manageable.

Participants across six continents signed up for my graduate-level classes when I decided to open them up to the world during the pandemic. Zulip became a central hub for asynchronous Q&A and posting Zoom links for lectures, whiteboard PDFs, and announcements. Zulip’s topics, and the ability to change the topic of someone else's message, has made it much easier for me to keep things coherent. It’s super easy to discuss technical material using the TeX integration, and spoilers are a great way to answer questions about homework without depriving students of a chance to keep thinking about the problem on their own.