How to Build a Custom AI Chat Application with Next.js: Fine-Tune GPT Using Your Data

AI specialists can now create highly personalized chatbots by fine-tuning OpenAI's GPT-4.1 models with their own data and building custom Next.js applications, transforming generic AI into domain-specific assistants that understand particular businesses, coding styles, and brand voices. This comprehensive tutorial demonstrates the complete process from web scraping and data preparation through model training to deploying a production-ready chat interface, offering developers an alternative to generic chatbots that provides consistent personality and specialized knowledge without requiring complex prompt engineering.