Chrome extension development

Workflows for developing and testing Chrome extensions using Claude in Chrome MCP tools. Enables a tight feedback loop: make code changes, reload the extension, navigate to test pages, and verify behaviour visually.

Prerequisites

Extensions Reloader

The test workflow requires the Extensions Reloader extension to be installed in Chrome.

Before first use, verify it's installed: Navigate to http://reload.extensions/. If the page loads (even with an error page), Extensions Reloader is installed and working. If navigation fails entirely, direct the user to install it: https://chromewebstore.google.com/detail/fimgfedafeadlieiabdeeaodndnlbhid

Dev bridge

Chrome extension keyboard shortcuts (registered via manifest.json commands or chrome://extensions/shortcuts) are intercepted by Chrome before reaching any page. Simulated keypresses from javascript_tool or computer tool cannot trigger them. The same applies to clicking the extension toolbar icon—it's outside the page viewport.

To trigger extension actions programmatically, extensions need a dev bridge: a small permanent snippet that forwards postMessage calls from the page context to the extension's message system.