OpenAI recently launched ChatGPT Atlas, a web browser where the LLM acts as your co-pilot across the internet. The browser allows users to ask questions about any page, have ChatGPT complete tasks, or let it browse in Agent mode while users work on something else. Delivering this experience required solving significant technical challenges around performance and responsiveness.

To build Atlas, OpenAI chose Chromium as the foundation, leveraging its proven performance, security, and web compatibility. However, the team faced ambitious goals: instant startup times, rich animations for features like Agent mode using modern native frameworks like SwiftUI and Metal, and support for hundreds of open tabs without performance degradation. Traditional Chromium integration would have required extensive modifications and custom patches that would complicate future updates.

OpenAI's solution was OWL (OpenAI's Web Layer), an architectural layer that runs Chromium as a separate process rather than embedding it directly. This approach uses IPC with Mojo for communication between the Atlas application and Chromium's browser process. The architecture enables rapid experimentation, faster feature delivery, and maintains OpenAI's engineering culture of "shipping on day one" where new engineers make code changes their first afternoon.