Building a short video and live streaming app like TikTok and Instagram starts with understanding your audience. Include essential features such as video recording, editing tools, filters, music, user profiles, likes, comments, and sharing. Add live streaming with chat and virtual gifts to encourage interaction. Choose a reliable backend, efficient video storage, and adaptive streaming for smooth playback across devices. Prioritize privacy, content moderation, and secure authentication. Begin with a minimum viable product, test performance, and collect user feedback. Gradually introduce personalized recommendations and monetization options while improving stability, usability, and the overall experience as your community continues to grow.