What is WebBrain?
WebBrain is a browser extension for Chrome, Edge and Firefox that adds an AI agent in a side panel. It answers questions about the page you are on and, in Act mode, clicks, types, navigates, fills forms and downloads files inside your normal signed-in browser. A Dev mode adds page source, console, network and reversible page edits. It is written by Emre Sokullu and contributors; the repository was created in April 2026.
It runs on three kinds of model. The default, WebBrain Compass 1.0, is a hosted service at api.webbrain.one with a free daily allowance and no key to set up. You can instead bring a key for one of 117 built-in provider cards on Chromium, among them OpenAI, Anthropic, Gemini, Bedrock and OpenRouter, or point it at a local OpenAI-compatible server such as llama.cpp, Ollama, vLLM or LM Studio. An MCP server lets Claude Code, Codex and Cursor hand it tasks.
The extension is free under GPL-3.0-or-later from version 33.0.0; the project began under MIT. A Compass subscription costs $5 a month per device profile. Help Improve WebBrain, on by default, lets WebBrain keep Compass prompts, responses and page text for model training.
How much does WebBrain cost?
| Plan | Price | What you get |
|---|---|---|
| Extension | Free | GPL-3.0-or-later; your own key or a local model |
| Compass free | Free | Daily allowance, size not published |
| Compass subscription | $5/month | Per device profile, under fair use |
Extension free under GPL-3.0-or-later. WebBrain Compass, the default hosted model, has a free daily allowance (size not published) and a $5/month subscription per device profile under a fair-use policy. Your own API key or a local model costs only what that provider or your hardware costs.
Is WebBrain worth it?
WebBrain's README lists more than most side-panel agents attempt: separate Ask, Act and Dev modes, saved and taught workflows, scheduled tasks, page watches, a screenshot-only vision mode and an MCP bridge for coding agents. It is also moving very fast. Version 45.0.4 shipped on 30 October 2026, and the major number rose from 38 to 45 during October. The repository has about 1,580 stars and 196 forks; the Chrome Web Store counts 2,000 users and a 4.0 rating from 24 reviews, and Firefox Add-ons 196 daily users. By those numbers it is young and small.
The default deserves the first look. Out of the box the panel runs on WebBrain Compass, which sends your prompt, page text and screenshots to api.webbrain.one and on through OpenRouter to an upstream model the privacy policy does not name. A setting called Help Improve WebBrain is on by default, and while it is on WebBrain may keep Compass prompts, responses, page text, tool calls and agent actions to fine-tune and train its models. Raw records are kept for up to 12 months and de-identified ones for up to 5 years, with a copy in an OpenRouter log retained for at least three months. Turning the switch off under Settings, Advanced stops new collection. Requests to your own API key or a local server bypass Compass entirely, and the extension carries no analytics or crash-reporting SDK.
The permissions are as broad as Chrome allows. The manifest asks for all URLs, cookies, the debugger, clipboard reading and tab capture, injects scripts into every frame of every page, and replaces the new tab page. The project's own security model is blunt about it: every site you are signed into, banking and email included, is open to the agent with your full rights. Its prompt-injection defence is more careful than most. Page text is wrapped as untrusted data, and a deterministic gate asks you to allow each consequential action per site, with no model in the decision. The weak points are the overrides. A 'Dangerously skip permissions' button turns the gate off, a default-on setting lets fetch_url send write requests to an approved host without a further prompt, and a question left unanswered for 60 seconds defaults to finishing the task, though anything touching payments, deletions or credentials falls back to the safe option.
GitHub's licence label is wrong. It reports NOASSERTION, but the LICENSE file grants GPL-3.0-or-later for version 33.0.0 onwards, chosen because the extension bundles GPL-licensed Xapian and libzim code; earlier versions were MIT, and the Firefox listing still says MIT. The GPL lets you use, modify and sell WebBrain, inside a company or not, but anyone who distributes a modified build must publish its source under the same licence.
Against Nanobrowser, the better-known open-source side-panel agent with 14,210 stars under Apache-2.0, WebBrain offers far more providers, in-browser WebGPU models and a paid hosted fallback. Against Browser Use or Stagehand it is a different tool: an assistant for a person at the keyboard rather than a library for unattended pipelines. Firefox users get a weaker build with no Chrome DevTools Protocol, which means no shadow-DOM piercing and no trusted mouse events, so some React and Vue buttons will not respond.
Where it earns its place
A researcher at a law firm who may not send client pages to a cloud model
Summarise and pull figures from documents in a signed-in research portal
Point WebBrain at a local llama.cpp or Ollama server and stay in read-only Ask mode, so nothing reaches WebBrain or a cloud provider. Size the model's context window first: the docs say 16k is only a fallback and the larger tool tiers can exceed it before history builds up.
A developer using Claude Code or Codex every day
Let the coding agent check pages behind SSO without scripting a login
Add the server with npx -y @webbrain/mcp-server, paste its pairing key under Settings, Bridge, and the agent gets six task-level tools such as webbrain_run and webbrain_extract against the signed-in browser. Act runs still stop for the in-browser approval prompts, so someone has to be at the screen.
An office manager at a small agency with no developer
Fill the same supplier order forms every week
Run the task once in Act mode, save it with /workflow --save and re-run it with new values; /schedule can repeat it while the browser is open. On Compass that costs $5 a month per device profile after the free allowance, and Help Improve WebBrain should be switched off first, since form contents would otherwise be eligible for training.
Before you commit
- Setup
- Install from the Chrome Web Store, Firefox Add-ons or Edge Add-ons and the Compass default works with no key. Local models need an OpenAI-compatible server and a provider card. Firefox needs version 140 or newer, and the Chrome store build (42.3.1, updated 21 October 2026) trails GitHub's 45.0.4.
- Integrations
- 117 provider cards on Chromium (116 on Firefox), covering OpenAI, Anthropic, Gemini, Azure OpenAI, Bedrock, OpenRouter and local runtimes; an MCP server for Claude Code, Codex, Cursor and OpenClaw; an LM Studio plugin; optional CAPTCHA services on your own keys.
- Data and privacy
- No analytics SDK. Compass requests go to api.webbrain.one and OpenRouter; with Help Improve WebBrain on, the default, eligible text is kept up to 12 months raw and up to 5 years de-identified for training. Own-key and local requests are not collected unless you enable per-provider research sharing, which is off by default. Licence is GPL-3.0-or-later from 33.0.0.
- Cost at scale
- Free on your own key or hardware, with per-provider cost allowances in Settings. Compass is $5 a month per device profile, so ten people pay $50 a month; the fair-use policy rules out automated or unusually high-volume use, and the subscription is tied to a device identifier, not refunded if that is lost. Compass XL uses credits at five times the standard rate.
- Limits
- Runs stop at 130 steps by default (195 at most). Firefox lacks the Chrome DevTools Protocol, so trusted mouse events and shadow-DOM piercing are Chrome-only. The website FAQ still calls llama.cpp the default provider, so the docs lag the code. Nine issues are open.
What’s good
- Runs on 117 provider cards, local servers or in-browser WebGPU
- Per-site permission gate that uses no model to decide
- Ask mode is read-only; actions need your own request
- MCP server lets coding agents use your signed-in browser
What’s not
- Hosted default keeps prompts for training unless switched off
- Can read every site and cookie you have, by design
- Major version went from 38 to 45 in one month
- Firefox build lacks trusted clicks and shadow-DOM access
Best for
Individuals who want a side-panel browser agent on their own API key or a local model and will take ten minutes to audit its defaults.
WebBrain alternatives
WebBrain: common questions
- Is WebBrain worth it?
- WebBrain gives you a capable agent inside your real browser for nothing, but its hosted default keeps your prompts for training until you find the switch, so run it on your own key or a local model. We rate it 3.7 out of 5.
- How much does WebBrain cost?
- Extension free under GPL-3.0-or-later. WebBrain Compass, the default hosted model, has a free daily allowance (size not published) and a $5/month subscription per device profile under a fair-use policy. Your own API key or a local model costs only what that provider or your hardware costs.
- What are the downsides of WebBrain?
- Hosted default keeps prompts for training unless switched off; can read every site and cookie you have, by design; major version went from 38 to 45 in one month; firefox build lacks trusted clicks and shadow-DOM access.
- Who is WebBrain best for?
- Individuals who want a side-panel browser agent on their own API key or a local model and will take ten minutes to audit its defaults.
- How much does WebBrain cost for a team or in production?
- Free on your own key or hardware, with per-provider cost allowances in Settings. Compass is $5 a month per device profile, so ten people pay $50 a month; the fair-use policy rules out automated or unusually high-volume use, and the subscription is tied to a device identifier, not refunded if that is lost. Compass XL uses credits at five times the standard rate.
- Is WebBrain safe for company data?
- No analytics SDK. Compass requests go to api.webbrain.one and OpenRouter; with Help Improve WebBrain on, the default, eligible text is kept up to 12 months raw and up to 5 years de-identified for training. Own-key and local requests are not collected unless you enable per-provider research sharing, which is off by default. Licence is GPL-3.0-or-later from 33.0.0.
- What are the best WebBrain alternatives?
- The closest alternatives we have reviewed are BrowserOS, Browser Use and OpenCLI.
Answers checked Oct 31, 2026.