Wrtn Leverages GPT-5 to Build Lifestyle AI for Millions in Korea

Wrtn, a Korean AI company, has successfully scaled its AI apps to 6.5 million users in Korea using GPT-5, OpenAI's latest model. The company is now planning to expand its model across East Asia. Wrtn initially focused on individual productivity with AI-powered writing assistants and note-taking tools. However, their vision evolved to create a 'Lifestyle AI' that integrates seamlessly into daily life, especially within Korea’s character-driven digital culture. "We realized the real opportunity was in AI that made discovery and creativity approachable for everyone," said Amp Park, AI Lead at Wrtn. Wrtn’s product suite, including AI Supporter, Labs, and Crack, has seen significant growth, including doubled retention and quadrupled time spent per user. The user base has expanded from students to professionals and families. One key challenge was nuanced localization for Korean. With GPT-4 and GPT-4.1, the AI's tone improved, incorporating slang, humor, and internet expressions. Wrtn layered in system prompt injections, persona-based role guidance, and temperature tuning to further enhance human-like responses. Wrtn uses a router architecture, directing traffic with lightweight models like GPT-4o mini and GPT-4.1 mini, while heavier tasks use GPT-4.1 and multimodal TTS. The launch of GPT-5 led to immediate increases in users and engagement, with an 8% increase in daily active users within a week due to improved instruction adherence, context handling, and personalization. Wrtn’s success demonstrates how advanced AI models can be made accessible and useful for millions in learning, creativity, and communication.