Question: I need a chat API that can be easily integrated into my app and offers a customizable UI.

If you're looking for a chat API with a customizable UI, TalkJS is another good option. It's a full-featured chat platform that supports 1-on-1 and group chats, AI chatbots, and customizable styling. TalkJS includes a pre-built UI and features like out-of-the-box notifications, moderation tools, and analytics. The platform is multi-platform compatible and includes a free development mode for testing and development.

Another good option is Sendbird, which offers a broad communications API that spans chat, SMS, WhatsApp, voice and video. Sendbird offers very abstracted APIs and SDKs with UI kits for several platforms. It's got a strong reputation for security and compliance, so it's a good fit for many industries. The service also offers features like targeted messaging and group chat, and has several pricing tiers including a free developer plan.

Stream is another option if you need a scalable API for social networks and chat apps. It's got a powerful Chat Messaging API with offline support and global EDGE network, along with sophisticated moderation tools. Stream's APIs and SDKs are designed to be easy to use, and the company offers copious documentation and UI kits to let you build rich social experiences quickly.

Finally, Meya is a customizable chatbot platform that's good for building sophisticated customer support systems. With features like advanced mobile and web chat UI, NLU integration and lots of customization options, Meya works with mobile and web apps. It offers a free 14-day trial and scalable pricing plans, so it's good for businesses large or small.