Why an agent browser can resemble ordinary browser traffic

Agentic browsers that run in the user's own browser present to websites as ordinary Chrome and carry no robots.txt token. ChatGPT Atlas (launched 21 October 2025 on macOS, with agent mode in preview) and Perplexity Comet are Chromium builds whose user-agent and client-hint brands HUMAN Security found effectively indistinguishable from Google Chrome (December 2025); Chrome's own Gemini auto browse (January 2026, US AI Pro and Ultra subscribers, preview) acts inside Chrome. OpenAI says it honours a GPTBot disallow for page content acquired through users' Atlas sessions and advises ARIA roles, labels and states so its agent can interact with pages. OpenAI deprecated Atlas, which was scheduled to stop working on 9 August 2026, moving browser-based agentic work into the ChatGPT desktop app and a Chrome extension or sidebar. Only cloud-hosted agents (Google-Agent, OpenAI's signed Cloud browser) identify themselves.