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You have an idea. Now build it. This guide walks you through writing your first prompt, understanding what gets generated, and testing the result live in Chrome.

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Pick something to build

Not sure where to start? These three prompts are beginner-friendly — each produces a complete, testable extension with immediate, visible results.
Prompt: “Build a Chrome extension that highlights every price on a webpage in green and shows a floating badge in the bottom-right corner with the total count of prices found.”What gets generated: A content.js file that scans the page for currency symbols ($, £, €), wraps matching text in a styled <span>, and injects a floating badge into the DOM.
Prompt: “Build a 25-minute Pomodoro timer in a popup. It should have Start, Pause, and Reset buttons and show a browser notification when time is up.”What gets generated: A popup.html, popup.css, and popup.js with a countdown timer. A background.js service worker keeps the timer running even when the popup is closed.
Prompt: “Build an extension with a toolbar button that toggles dark mode on the current webpage by inverting all colors.”What gets generated: An action-based extension that uses chrome.scripting.executeScript to inject a CSS filter into the active tab on each toolbar click.

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Write your prompt

Open the Extensy editor and describe what you want. The more specific you are, the better the output. A strong first prompt covers four things:
  1. Goal — “Build a Chrome extension that…”
  2. Target — “…on wikipedia.org” or “…on every webpage”
  3. Action — “…highlights all prices” or “…shows a popup with a timer”
  4. UI — “…with a green floating badge in the bottom-right corner”
You don’t need to know any code. Write the prompt the same way you’d explain the idea to a friend.

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Generate the extension

Click Generate. Extensy’s AI pipeline analyzes your request and produces a complete extension package — manifest, scripts, popup files, and icons. Generation typically takes 10–30 seconds.

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What you get

Every generated extension is a complete Chrome extension package following Manifest V3. Depending on your prompt, it may include:
Not every extension needs all these files. A simple popup tool may have no content.js. Extensy only generates what your prompt actually requires.

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Download and load in Chrome

1

Download the ZIP

Click Download ZIP from the Extensy dashboard and save the file to your computer. Extract it into a regular folder.
2

Open chrome://extensions

Navigate to chrome://extensions in Chrome.
3

Enable Developer mode

Toggle Developer mode on in the top-right corner.
4

Load unpacked

Click Load unpacked and select the unzipped folder.

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Test it

Open a tab that matches your extension’s target and trigger the behavior — click the toolbar icon, visit a page with prices, or start the timer.
If nothing happens immediately, check the toolbar. Your extension may be popup-based and only activates when you click its icon. You might also need to pin it first via the puzzle-piece menu.

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Common first-timer mistakes

  • Vague selectors — If you ask the extension to click a button but don’t name it, the AI will guess. Include the exact button label or ID when possible.
  • Missing permissions — If your extension calls an external API, mention it in your prompt so Extensy can add the correct host_permissions to manifest.json.
  • Stale tabs — Content scripts don’t inject into tabs that were already open when you loaded the extension. Refresh any existing tabs after loading.

Prompting guide

Learn the anatomy of a great Extensy prompt and templates for every category.

Load in browser

Full step-by-step instructions for Chrome Developer Mode.