Chrome Extension Manifest Generator

Manifest V3 (MV3) is the current Chrome extension platform. It replaced Manifest V2 with service workers instead of background pages, declarativeNetRequest instead of blocking webRequest, and stricter content security policies. Google began enforcing MV3 in 2024 — all new extensions must use MV3, and all existing MV2 extensions were sunset from the Chrome Web Store.

permissions covers API access (storage, tabs, notifications, etc.) — Chrome features your extension can use. host_permissions covers which websites your extension can access (inject scripts, read cookies, make requests). In MV3 these are separate: APIs go in permissions[], website patterns go in host_permissions[]. Both require user consent during install.

Content scripts run in the context of web pages — they can read and modify page DOM, interact with the page's JavaScript environment, and listen to page events. Background service workers handle events not tied to a specific page: alarms, messages, network requests via fetch, or responding to browser events. They wake on demand and sleep when idle.

Follow least-privilege: only request what you actually use. For a simple popup that reads/writes settings: just storage. For reading the current tab URL: activeTab (granted on user click, no prompt). For scripting injection: scripting + host_permissions for the target sites. Chrome may warn users about 'sensitive permissions' — keep the list lean to improve install conversion.

Create icon PNG files at 16x16, 32x32, 48x48, and 128x128 pixels. Place them in an icons/ folder. Reference them in manifest.json under both the top-level icons (for the extensions page) and action.default_icon (for the toolbar button). For best results, use a transparent background and test on both light and dark Chrome themes.

Open chrome://extensions in Chrome, enable 'Developer mode' (top right toggle), click 'Load unpacked', and select your extension folder containing manifest.json. Chrome loads the extension and shows any manifest errors. After code changes, click the refresh icon next to your extension to reload it without reinstalling.