Meet WebBrain: An Open-Source, Local-First AI Browser Agent That Reads Pages and Automates Tasks in Chrome and Firefox

WebBrain is a free, open-source browser agent for Chrome and Firefox. It reads pages, extracts data, and automates multi-step tasks. Unlike most browser AI plugins, it can also run entirely on a local model. It is built by Emre Sokullu and licensed under MIT. The full source lives on GitHub. Run the agent against a local model, and no page data leaves your machine. Connect a cloud API when you want more capability. What is WebBrain? WebBrain lives in your browsers side panel. In Chrome it uses Manifest V3 and the sidePanel API. In Firefox it uses Manifest V2 and sidebar_action. Each tab keeps its own conversation history. The extension operates inside your existing authenticated session. It sees your logged-in accounts exactly as you do. It stores no data externally and adds no telemetry or accounts. The plugin ships in English, Español, Français, Türkçe, and 中文. It auto-detects your browser language on first launch. Ask Mode, Act Mode, and How Actions Actually Fire WebBrain has two modes: Ask mode is read-only and cannot change the page. Act mode can click, type, scroll, navigate, and run workflows. Ask mode reads pages through ordinary content scripts. Act mode is different. It drives the page through the Chrome DevTools Protocol via the chrome.debugger API. That produces trusted input events that modern sites actually honor. It also reaches cross-origin iframes and shadow DOM that content scripts cannot see. That power is scoped deliberately. WebBrain attaches the debugger only when an action needs it, per tab. Chrome surfaces its standard ‘WebBrain started debugging this browser’ banner while attached. Firefox has no CDP equivalent, so its Act mode is meaningfully weaker. Temperatures are fixed for predictability. Act mode uses temperature 0.15. Ask mode uses 0.3. Dedicated vision screenshot descriptions use 0. The Security Model Browser agents run on an adversarial surface. Web pages can hide prompt injections that hijack an agents behavior. WebBrains design ad