Claude, Codex, and Gemini Are All in the Browser Now: Comparing Three AI Agent Approaches in Chrome

TL;DR Anthropic builds an extension, OpenAI builds its own browser, Google welds AI directly into Chrome — three completely different approaches. Here's a comparison of the current landscape, key differences, and a selection guide.

#ai-agent #chrome-extension #claude #codex #chatgpt-atlas #gemini #browser-agent

Table of Contents

Claude for Chrome
ChatGPT Atlas + Codex Chrome Extension
Gemini in Chrome
Three-Way Comparison
The Big Picture
References

🌏 中文版

From early 2026 through May, all three major AI vendors brought agents into the browser — but each took a completely different approach. Anthropic built a Chrome extension, OpenAI built its own browser Atlas and added a Codex extension, and Google welded Gemini directly into Chrome itself. This post covers where each stands, how their strategies differ, and how to choose.

Claude for Chrome

Anthropic went the “extension” route. It launched as a research preview in August 2025, limited to 1,000 testers. By 2026 it entered beta, and now all paid plans have access.

The design philosophy is “meet users where they already are”: no browser switch required, no fight over the default search engine. It sits in a Chrome side panel. It sees the same content you do and can click, fill forms, operate across tabs, and execute multi-step workflows. Claude Code’s Chrome integration (beta) follows the same line, targeting developers.

The permission model leans conservative: sensitive sites require per-site authorization by default. There’s a good reason for this — in 2026, LayerX disclosed a vulnerability called ClaudeBleed, showing that any Chrome extension (even without special permissions) could inject instructions to hijack the Claude extension. Anthropic shipped v1.0.70 on 2026-05-06, adding a secondary confirmation flow for sensitive operations.

Best for: people who want to stay in Chrome, don’t want to switch ecosystems, and are already paying Claude subscribers. Not ideal for: power users who want an agent to take over their entire browsing workflow — Anthropic deliberately confines it to the side panel.

ChatGPT Atlas + Codex Chrome Extension

OpenAI is playing two games at once.

ChatGPT Atlas is OpenAI’s own Chromium-based browser with a built-in ChatGPT sidebar and Agent Mode (Plus / Pro / Business preview). Agent Mode is faster than earlier versions and can research, plan trips, and automate tasks directly within tabs. Currently macOS only; Windows / iOS / Android are planned.

Codex Chrome Extension, released on 2026-05-07, is an entirely separate play targeting developers. It lets Codex leverage your already-signed-in browser sessions to operate LinkedIn, Salesforce, Gmail, and internal company tools. It pulls context across tabs and uses DevTools, but deliberately avoids taking over the entire browser. Not available in the EU or UK.

The two lines coexist for now, but OpenAI announced in 2026-03 that it plans to merge Atlas + the ChatGPT desktop app + Codex into a single desktop application — the current split is a transitional phase.

Design philosophy: control the entire browsing surface. Atlas isn’t an extension; it’s a browser. An agent can do far more when it owns the runtime rather than living inside someone else’s browser. The tradeoff is asking users to switch browsers.

Best for: people willing to switch browsers, those wanting the deepest agent integration, or developers who need signed-in session access to SaaS tools. Not ideal for: European users (Codex extension not yet available), anyone who doesn’t want to leave Chrome.

Gemini in Chrome

Google is the only one that requires zero installation — Gemini is already built into Chrome.

Starting 2026-01-28, a new Gemini 3-based sidebar rolled out on Windows / macOS / Chromebook Plus in the US, expanding to APAC in 2026-04. The highlight is Auto Browse: agentic multi-step operations (price comparison, hotel booking, form filling, subscription management), currently in preview for Google AI Pro / Ultra subscribers.

The design philosophy is first-party integration: Gemini isn’t bolted onto Chrome; it’s part of Chrome. This enables things others simply can’t do: deep integration across Google Apps (Gmail / Drive / Calendar), no authorization steps needed (Chrome’s existing permissions are inherited directly), and a future path toward Personal Intelligence.

The tradeoff is lock-in to the Google ecosystem. For heavy Gmail / Drive / Calendar users, this is the smoothest option. For people who don’t want to hand more data to Google, it’s also the hardest to refuse — because it’s just there once Chrome updates.

Best for: Google power users, AI Pro / Ultra subscribers, anyone wanting a zero-friction experience. Not ideal for: people who work across platforms and ecosystems.

Three-Way Comparison

Vendor	Form Factor	Model / Price Threshold	Regional Restrictions	Setup Cost
Anthropic	Chrome extension (beta)	Any paid plan	—	Install extension
OpenAI	Atlas browser + Codex extension	Plus/Pro/Business (Atlas); Codex subscribers	EU/UK no Codex	Switch browser or install extension
Google	Built into Chrome + side panel	AI Pro/Ultra (Auto Browse)	US first, APAC now available	None

The Big Picture

The three approaches really represent three different answers to “where should an agent live”:

Anthropic: Piggyback on the user’s existing browser — cautious, incremental, safety-model-first.
OpenAI: Build your own browser — agent-first, browsing-second; supplement with an extension for developer scenarios.
Google: Use the existing Chrome distribution channel to deliver AI directly to everyone’s desktop.

Decision criteria for choosing:

Which one are you already paying for? All three have paid tiers as prerequisites — start with your existing subscription.
Are you willing to switch browsers? Yes → Atlas offers the most complete experience. No → Claude extension or Gemini in Chrome.
What tasks do you need? Developer scenarios with signed-in sessions → Codex extension. Personal assistant, research, trip planning → Atlas Agent Mode or Gemini Auto Browse. Blended into your workflow while keeping you in control → Claude for Chrome.

Short-term outlook: once Atlas + Codex merge, OpenAI will have the most complete agent stack. Gemini will capitalize on Chrome’s massive distribution advantage. Claude will maintain its “most cautious, most trustworthy” positioning. Over the next year, these three trajectories will continue to diverge, not converge.