AI browser assistants now follow a familiar pattern: a panel beside the page can read what you are viewing and, with permission, act on it. Claude for Chrome, Gemini in Chrome, ChatGPT's browser tools, and Perplexity Comet all use some version of this idea.
Kilo Code is the model-agnostic, open-source alternative in this category. It adds an AI side panel to Chrome or Firefox, reads the selected tab, can act on the page when you explicitly enable Danger mode, and lets you choose from 500+ models across 60+ providers. The extension is MIT-licensed and free; inference can use Kilo Gateway at provider rates, your own API keys, free models, or Auto Free.
The tradeoff is maturity. Kilo Code's browser extension launched at version 0.1.1 in July 2026. It currently reads one selected tab at a time and limits a run to 20 tool rounds. Claude for Chrome and Perplexity Comet are further ahead for long, multi-tab browser automation.
This comparison was checked against official product pages and documentation on July 27, 2026. Browser-agent features, regional availability, and pricing change quickly, so verify plan details before buying.
TL;DR: Which AI browser extension is best?
| Your priority | Best fit | Why |
|---|---|---|
| Open-source, model-agnostic assistance in Chrome or Firefox | Kilo Code | 500+ models, 60+ providers, MIT license, BYOK, free-model options, Read-only and Danger modes |
| Polished browser automation in Chrome | Claude for Chrome | Strong click, form, multi-tab, Claude Code, and Cowork workflows |
| Native Chrome and Google app integration | Gemini in Chrome | Built into Chrome with open-tab context and Google ecosystem connections |
| OpenAI browser workflows | ChatGPT | Browser capabilities are moving from Atlas into ChatGPT, Codex, and a Chrome extension/sidebar |
| Most capable AI-native browser | Perplexity Comet | Strong multi-step and multi-tab workflows, but requires switching browsers |
| Multi-model sidebar with bundled creative tools | Sider or Monica | Broad model access plus writing, image, video, and document tools |
| Scripted monitoring and browser automation | HARPA AI | Reusable commands, scheduled tasks, page monitoring, automation, and BYOK |
| Open-source, keys-only multi-agent automation | Nanobrowser | Apache-2.0, Chrome and Edge support, local execution, and user-supplied keys |
Short answer: choose Kilo Code when your main requirements are model choice, open-source code, transparent inference costs, Firefox support, and an extension that stays in your current browser. Choose a first-party tool when you already pay for its ecosystem and want its deepest integrations. Choose Comet when autonomous multi-tab work matters more than keeping your current browser.
What is the Kilo Code browser extension?
The Kilo Code browser extension is an AI browser agent for Chrome and Firefox. It stays open in the browser side panel and grounds answers in the page you have selected. Typical uses include summarizing an article, explaining a dashboard, searching a long document, and extracting structured information without copying content into another tab.
Read-only mode
Read-only mode is designed for questions that do not require page interaction. Its tools can retrieve a sanitized snapshot of the selected page, search text in that snapshot, inspect element details, capture an optional viewport screenshot for vision-capable models, and search local memories.
Read-only mode cannot click, type, navigate, submit forms, read cookies, or read browser storage. That smaller permission surface is useful when you want grounded answers without giving an agent control of the page.
Danger mode
Danger mode adds one tool: eval. It runs model-authored JavaScript in the selected tab, through the Chrome debugger protocol or Firefox scripting API. Instead of selecting from a fixed vocabulary such as click, type, and navigate, the model can perform operations available from the page's JavaScript context.
That design is flexible, but it also deserves the name. Kilo instructs the agent to request confirmation before irreversible, financial, authentication-related, privacy-sensitive, or externally communicating actions. Use Read-only mode unless a task genuinely requires interaction.
Remote MCP tools and local memories
Kilo Code can connect to remote Model Context Protocol (MCP) servers over OAuth. Tools from a connected server appear as callable functions in the side panel, and each server can be allowed or blocked in Read-only mode. Among the browser assistants reviewed here, Kilo is the only one we found documenting remote MCP tools directly in the side panel.
The extension also keeps local memories. You can add a page to memory from the context menu and let the agent search those saved memories during later sessions.
Model choice and cost
Kilo Gateway provides 500+ models from 60+ providers, including frontier proprietary models, open-weight models, free models, and automatic routing. Kilo charges exact provider rates without an inference markup. You can also bring your own keys or use local models through tools such as Ollama and LM Studio.
This is Kilo's main structural difference from Claude, Gemini, and ChatGPT browser products: the browser workflow is not coupled to one model vendor. A cheap, fast model can summarize a page, while a stronger reasoning model can handle a difficult analysis, without changing extensions.
AI browser extensions and agents compared
| Product | Runs in | Reads pages | Acts on pages | Model choice | Cost model | Open source |
|---|---|---|---|---|---|---|
| Kilo Code | Chrome, Firefox | Yes, one selected tab | Yes, JavaScript eval in Danger mode | 500+ models across 60+ providers, including free and open-weight models | Free extension; provider-rate inference, BYOK, or Auto Free | Yes, MIT |
| Claude for Chrome | Desktop Chrome | Yes | Yes, including navigation, clicks, and forms | Anthropic models | Available on paid Claude plans | No |
| Gemini in Chrome | Chrome | Yes, including context from open tabs | Auto-browse where eligible | Gemini models | Reading features vary by region; auto-browse starts on eligible paid plans | No |
| ChatGPT browser tools | ChatGPT desktop and Chrome extension/sidebar where available | Yes | Browser workflows where available | OpenAI models | Availability depends on plan, region, device, and workspace | No |
| Perplexity Comet | Comet browser on macOS, Windows, iOS, Android | Yes | Yes, including multi-step tasks | Perplexity-selected model access; premium models depend on plan | Free browser with paid Perplexity tiers | No |
| Sider | Browser extension and desktop/mobile apps | Yes | Browser automation features | Multiple frontier models | Credit-based free and paid plans | No |
| Monica | Chrome extension and apps | Yes | Browser Operator | Multiple text, image, and video models | Credit-based plans | No |
| HARPA AI | Chrome extension | Yes | Yes, including reusable and scheduled commands | Multiple hosted models plus BYOK | Free limits, token plans, BYOK, and lifetime option | No |
| Nanobrowser | Chrome, Edge | Yes | Yes, multi-agent automation | Supported providers, Ollama, and OpenAI-compatible endpoints using your keys | Free extension; you pay provider or local inference costs | Yes, Apache-2.0 |
The products fall into four practical groups:
- Single-vendor browser assistants: Claude for Chrome, Gemini in Chrome, and ChatGPT. They integrate deeply with one lab's models and products but do not offer cross-provider model choice.
- AI-native browsers: Perplexity Comet. These can redesign the whole browsing experience around agents, but adoption means moving your browser data and habits.
- Multi-model commercial sidebars: Sider, Monica, and HARPA AI. They bundle multiple models and browser features, usually behind credits, token allocations, or subscriptions.
- Open-source BYOK browser agents: Kilo Code and Nanobrowser. Their code and licenses are public, and users have more control over model routing and costs.
Kilo Code vs Claude for Chrome
Claude for Chrome is the strongest choice for a polished Anthropic-native browser workflow. It can navigate, click, fill forms, work across tabs, run background tasks, and connect browser work with Claude Code and Cowork. Anthropic describes it as a beta available on paid Claude plans.
Kilo Code is the better fit if you need Firefox, open-source code, or models outside Anthropic. It also lets you use less expensive open-weight or free models for routine page reading instead of spending premium-model tokens on every task.
Choose Claude for Chrome if you already use a paid Claude plan and want mature multi-tab automation. Choose Kilo if model freedom and browser choice matter more than maximum autonomy today.
Kilo Code vs Gemini in Chrome
Gemini in Chrome has two advantages Kilo does not currently match: native Chrome integration and context from multiple open tabs. It also connects naturally to Google products such as Gmail, Drive, Keep, and YouTube.
Google's auto-browse capability can complete browser tasks for eligible Google AI Pro and Ultra users, but availability depends on region and plan. Kilo's Danger mode is available in both supported browsers and is not restricted to Gemini models.
Choose Gemini for comparisons across several open tabs or a Google-first workflow. Choose Kilo for Firefox, open-source implementation, broader model selection, or access to remote MCP tools.
Kilo Code vs ChatGPT after Atlas
OpenAI is discontinuing the ChatGPT Atlas browser and moving browser-based agent capabilities into ChatGPT and Codex. Atlas is scheduled to stop working on August 9, 2026. OpenAI advises users to export bookmarks and save important pages before the cutoff.
OpenAI says its replacement browser experience will include multiple tabs, downloads, improved navigation, account login support, and a ChatGPT Chrome extension or sidebar where available. Availability can depend on plan, region, device, browser, and workspace settings.
Kilo is available now from the Chrome and Firefox extension stores and is not tied to OpenAI models. ChatGPT remains the natural choice for people committed to the OpenAI ecosystem; Kilo is the better match for users who want a stable extension shape and cross-provider choice.
Kilo Code vs Perplexity Comet
Perplexity Comet is an AI-native browser designed for delegation. It can research across tabs, work with email, shop, and perform multi-step browser tasks. It is available on macOS, Windows, iOS, and Android.
Comet is more capable than Kilo for long autonomous sequences and multi-tab synthesis. The tradeoff is switching browsers and adopting Perplexity's product and plan structure. Kilo is a small extension added to Chrome or Firefox, so your bookmarks, passwords, extensions, and browsing habits stay where they are.
Choose Comet for maximum browser autonomy. Choose Kilo to add model-agnostic assistance to the browser you already use.
Kilo Code vs Sider, Monica, and HARPA AI
Sider, Monica, and HARPA AI are Kilo's closest commercial competitors for multi-model access.
Sider combines page chat, summarization, translation, browser automation, coding, and creative tools. Monica adds text, image, and video generation plus a Browser Operator. HARPA AI focuses on reusable commands, web monitoring, scheduled workflows, extraction, and automation, and it supports BYOK.
The main difference is the billing layer. These products package usage into credits, token allocations, subscriptions, or lifetime plans. Kilo Gateway bills model inference at provider rates without markup, while BYOK and free-model paths let users bypass hosted Kilo inference entirely.
Choose Sider or Monica if you want one subscription for browser help and creative-generation features. Choose HARPA for scripted monitoring and recurring automation. Choose Kilo when open-source code, Firefox support, remote MCP tools, and transparent model costs are the priority.
Kilo Code vs Nanobrowser
Nanobrowser is the closest open-source alternative in philosophy. It is Apache-2.0 licensed, runs locally as a Chrome or Edge extension, supports multiple provider and local-model options, and uses separate planning and navigation agents for browser automation.
Nanobrowser is a good fit if you already have provider keys and want a keys-only, multi-agent automation tool. Its official documentation does not currently list Firefox as supported.
Kilo adds a hosted path: start with Auto Free, pay provider rates through Kilo Gateway, or bring keys later. It also supports Firefox, remote MCP servers, local memories, and team features such as centralized billing, usage analytics, model restrictions, audit logs, and SSO.
Browser-agent security: read-only access vs automation
Browser agents process untrusted page content while operating inside sessions that may already be logged in. That creates a prompt-injection risk: text hidden or displayed on a page can attempt to redirect the model from the user's instruction. Anthropic, OpenAI, Google, and independent security researchers all describe prompt injection as an unresolved browser-agent problem.
Kilo treats page text, URLs, HTML, and tool results as data rather than instructions. Tab context is HTML-escaped before reaching the model, and URL query strings and fragments are removed. Danger mode also asks for confirmation before sensitive actions.
Those mitigations reduce risk; they do not eliminate it. The strongest control is capability restriction. In Read-only mode, Kilo cannot click, type, navigate, submit forms, inspect cookies, or access browser storage. For summarization, extraction, and page questions, use Read-only mode. Enable Danger mode only for a task that needs page interaction, review proposed actions, and avoid using browser agents for financial transactions or high-risk account changes.
Which AI browser assistant should you install?
Choose based on the constraint you care about most:
- Choose Kilo Code for a model-agnostic, open-source AI browser extension with Chrome and Firefox support, provider-rate inference, BYOK, free-model options, remote MCP tools, and a deliberate Read-only mode.
- Choose Claude for Chrome for polished, multi-tab automation connected to Claude Code and Cowork.
- Choose Gemini in Chrome for native Chrome integration, multi-tab context, and Google app workflows.
- Choose ChatGPT for OpenAI-native browser work as Atlas capabilities move into ChatGPT, Codex, and Chrome surfaces.
- Choose Perplexity Comet for the strongest autonomous browser experience when changing browsers is acceptable.
- Choose Sider or Monica for multi-model access bundled with broad writing and creative tools.
- Choose HARPA AI for monitoring, reusable commands, and scheduled browser automation.
- Choose Nanobrowser for open-source, keys-only, multi-agent automation in Chrome or Edge.
Kilo Code is the best fit when you want the same core browser-agent pattern without committing to one AI lab, one paid credit currency, or Chrome alone. Its limitations are concrete: version 0.1.1 is early, it reads one selected tab at a time, and a run stops after 20 tool rounds. If you need long autonomous workflows across many tabs, Claude for Chrome or Comet is more mature today.
If your workflow is page reading, grounded questions, structured extraction, optional page actions, and calls to your own MCP tools, Kilo gives you that workflow with model choice and open-source transparency.
Frequently asked questions
What is the best open-source AI browser extension?
Kilo Code is the best fit for users who want an open-source AI side panel in both Chrome and Firefox, access to 500+ models, hosted and BYOK options, remote MCP tools, and separate Read-only and Danger modes. Nanobrowser is a strong Apache-2.0 alternative for keys-only multi-agent automation in Chrome or Edge.
Is Kilo Code a Claude for Chrome alternative?
Yes. Both can read a page and act on browser content, but their architectures differ. Claude for Chrome is tied to Anthropic models and offers more mature multi-tab automation. Kilo Code is model-agnostic, MIT-licensed, available on Chrome and Firefox, and supports 500+ models across 60+ providers.
Does Kilo Code work in Firefox?
Yes. Kilo Code is available from Firefox Add-ons as well as the Chrome Web Store. Claude for Chrome, Gemini in Chrome, and HARPA AI are Chrome-focused, while Nanobrowser officially supports Chrome and Edge.
Can Kilo Code click and fill forms?
Kilo Code can act on a page when Danger mode is enabled. Instead of separate click and type tools, it provides an eval function that runs model-authored JavaScript in the selected tab. Read-only mode cannot click, type, navigate, or submit forms.
Can I choose which model powers the Kilo browser extension?
Yes. Kilo Gateway exposes 500+ models across 60+ providers, including frontier proprietary models, open-weight models, free models, and Auto routing. Users can also bring their own provider keys or use local model setups.
Is the Kilo Code browser extension free?
The extension is free. Inference can run on Auto Free, free models, your own API keys, local models, or paid models through Kilo Gateway at provider rates without markup.
Is the Kilo Code browser extension safe?
No browser agent is risk-free because web pages can contain malicious prompt injections. Kilo's Read-only mode limits the agent to page-reading capabilities and cannot click, type, navigate, submit forms, read cookies, or read storage. Danger mode is more powerful and should be enabled only when page interaction is required.
Official sources
The comparison uses official product pages, pricing pages, and project documentation retrieved on July 27, 2026.