Anthropic's Claude for Mac desktop app now has built-in browser

What happened

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Anthropic has shipped a built-in Chromium-based browser inside the Claude desktop application's Cowork mode, available on Mac, Windows, and Linux. The company announced the change on a Wednesday, positioning it as a way for Claude to navigate the web directly within the same environment where users already do their work, without requiring a separate extension or a separate browser window.

This article covers how the built-in browser differs from the existing Claude in Chrome extension, what access it has to existing logins, what security trade-offs Anthropic acknowledged in its own announcement, and who should pay attention to the settings change it introduces. It is aimed at developers and power users who run Claude in Cowork mode as part of a daily workflow.

How it works

Anthropic added a Chromium-based browser directly into Cowork, the desktop app mode for Claude available on Mac, Windows, and Linux. Before this change, letting Claude browse the web required installing the Claude in Chrome extension, which gave Claude access through a user's existing browser session. The company framed the extension approach as appropriate for pages a user already has open, but not for the broader class of web tasks that benefit from a fresh, separate browser context.

The update also arrives at a particular moment in the AI assistant market. OpenAI had previously announced Atlas, a stand-alone browser project, then changed direction and instead added built-in browsing to the ChatGPT desktop app. With the Claude desktop app now shipping the same capability, both major consumer-facing AI assistant applications offer integrated web access through their desktop clients rather than through independent browser products.

The built-in browser runs as a separate Chromium instance that Anthropic describes as "Claude's browser, not yours." Because it is isolated from the user's daily browser, it does not automatically carry over the user's existing login sessions. To bridge that gap, Anthropic built a credential import mechanism: on macOS, users can bring logins from Chrome, Edge, and Firefox, though banking, email, and single sign-on providers are explicitly excluded from that import by default unless the user manually overrides the restriction.

Why it matters

On Windows, only Firefox credentials can be imported. The asymmetry exists because Chrome and Edge on Windows implement infostealer countermeasures that prevent third-party applications from reading local cookies, while Firefox on any platform stores session data in an unencrypted SQLite database. Chrome on macOS stores its encryption keys in the system Keychain, which macOS permits authorized apps to read. This means the practical range of imported sessions differs by operating system and by which browser the user has installed.

The architectural shift matters because it changes the trust boundary. The Chrome extension model put Claude inside the user's existing authenticated session, which gave it broad access to any page currently open but also meant that access was bounded by what the user had loaded. A dedicated Chromium instance decoupled from the user's session creates a narrower attack surface for the sites Claude will most often visit during autonomous tasks, since it is unlikely to be logged into sensitive accounts.

Who is affected

Anthropic nonetheless made an explicit acknowledgment in its announcement that prompt injection risk is not eliminated. The company says it has built safeguards into both the Chrome extension and the built-in browser, but states that "the risk is not zero." Because the built-in browser is not signed into banking or email by default, the company reasons that if a prompt injection attack were to succeed, the blast radius would be smaller than it would be inside a fully authenticated personal browser session.

Anyone running the Claude desktop application on Mac, Windows, or Linux who uses Cowork is immediately affected, particularly users who previously relied on the Claude in Chrome extension for all web browsing tasks. Those users will need to check their settings, because if the Chrome extension is already installed, it remains the default browser for Claude to use rather than the new built-in one. Switching to the integrated Chromium browser requires explicitly changing the preferred browser in Claude Desktop settings.

Enterprise or team users who have configured Claude workflows involving web research or agentic tasks that touch third-party sites should audit which login credentials would transfer under the new system. Users on Windows specifically face a narrower credential import than macOS users. Developers building automation on top of Claude's Cowork mode should also verify whether their existing web-facing tasks assume the extension model or are agnostic to the underlying browser context.

What to watch next

The most concrete thing to verify in the coming weeks is whether the excluded credential categories hold firm. Anthropic says banking, email, and SSO providers are blocked from the credential import unless a user explicitly overrides the restriction, but the mechanism for that override is worth examining in practice to confirm how much friction is placed on high-risk approvals. A builder integrating Claude's web capability into an automated pipeline should also test whether the session isolation holds across restarts and whether any state leaks between Cowork sessions.

The Chrome extension itself is not going away. Anthropic is maintaining both paths, with the extension remaining the recommended tool for working on a page already open in the user's own browser with their own active accounts, such as editing a document, processing an inbox, or updating a CRM. The open question is whether Anthropic will eventually unify the two surfaces or keep them as distinct tools with distinct scopes, and whether the credential import list will expand or contract as the built-in browser matures.