The Architecture Behind Atlas: OpenAI’s New ChatGPT-based Browser

Sonar Summit: global conversation building software in the AI era (Sponsored)

Join us for Sonar Summit on March 3rd, a global virtual event, bringing together the brightest minds in software development.

In a world increasingly shaped by AI, it’s more crucial than ever to cut through the noise and amplify the ideas and practices that lead to truly good code. We created Sonar Summit to help you navigate the future with clarity and knowledge you need to build better software, faster.

OpenAI recently launched ChatGPT Atlas, a web browser where the LLM acts as your co-pilot across the internet. You can ask questions about any page, have ChatGPT complete tasks for you, or let it browse in Agent mode while you work on something else.

Delivering this experience wasn’t trivial. ChatGPT Atlas needed to start instantly and stay responsive even with hundreds of tabs open. To make development faster and avoid reinventing the wheel, the team built on top of Chromium, the engine that powers many other modern browsers.

However, Atlas is not just another Chromium-based browser with a different skin. Most Chromium-based browsers embed the web engine directly into their application, which creates tight coupling between the UI and the rendering engine. This architecture works fine for traditional browsing, but it makes certain capabilities extremely difficult to achieve.

Therefore, OpenAI’s solution was to build OWL (OpenAI’s Web Layer), an architectural layer that runs Chromium as a separate process, thereby unlocking capabilities that would have been nearly impossible otherwise.

In this article, we learn how the OpenAI Engineering Team built OWL and the technical challenges they faced around rendering and inter-process communication.

Disclaimer: This post is based on publicly shared details from the OpenAI Engineering Team. Please comment if you notice any inaccuracies.

Why Chromium?

Chromium was the natural choice as the web engine for Atlas. Chromium provides a state-of-the-art rendering engine with strong security, proven performance, and complete web compatibility. It powers many modern browsers, including Chrome, Edge, and Brave. Furthermore, Chromium benefits from continuous improvements by a global developer community. For any team building a browser today, Chromium is the logical starting point.

However, using Chromium comes with significant challenges. The OpenAI Engineering Team had ambitious goals that were difficult to achieve with Chromium’s default architecture:

• First, they wanted instant startup times. Users should see the browser interface immediately, not after waiting for everything to load.

• Second, they