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Before publishing your extension, load it directly into Chrome to test it. This takes under a minute using Chrome’s built-in Developer Mode.

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Load the extension

1

Download and unzip

Click Download ZIP from the Extensy dashboard and save the file to your computer. Extract it into a regular folder — Chrome needs the unzipped folder, not the ZIP file itself.
2

Open chrome://extensions

Type chrome://extensions into the Chrome address bar and press Enter. You can also get here by clicking the puzzle icon in the toolbar and selecting Manage extensions.
3

Enable Developer mode

Find the Developer mode toggle in the top-right corner of the page and turn it on. A row of new buttons will appear at the top-left.
4

Click Load unpacked

Click the Load unpacked button that appeared after enabling Developer mode.
5

Select your extension folder

A file browser opens. Navigate to the unzipped folder containing your extension files (the folder that holds manifest.json) and select it.
6

Verify it loaded

Your extension should now appear as a card on the chrome://extensions page. If there are any errors, an Errors button will appear on the card — click it to see details.

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Pin the extension to your toolbar

If your extension has a popup, pin it so it’s easy to access:
  1. Click the puzzle icon in the Chrome toolbar.
  2. Find your extension in the dropdown list.
  3. Click the pin icon next to it.
Your extension’s icon will now appear directly in the toolbar.

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Test your extension

Once loaded, verify it works as expected:
  • Popup-based extensions — Click the toolbar icon to open the popup and interact with it.
  • Content script extensions — Open a tab that matches your extension’s target site (e.g., wikipedia.org) and look for the injected UI or behavior.
  • Background event extensions — Trigger the event your extension listens for (e.g., opening a new tab, installing the extension) and check the result.
If you don’t see anything on the page, try refreshing the tab. Content scripts don’t inject into tabs that were already open when the extension was loaded.

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Reload after editing

When you make changes to the extension’s files, you don’t need to remove and re-add it. Instead:
  1. Save your file changes in your code editor.
  2. Go to chrome://extensions.
  3. Click the reload icon (↺) on your extension’s card.
  4. Refresh the tab you’re testing on.
Chrome does not hot-reload extensions. You must click the reload button on the extensions page manually after each change — the browser won’t pick up file edits automatically.

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Troubleshoot load errors

If the extension fails to load or behaves unexpectedly:
  • Click the Errors button on the extension card in chrome://extensions for a detailed breakdown of which file and line caused the issue.
  • Open Chrome DevTools (F12 or right-click → Inspect) on the page you’re testing. Check the Console tab for JavaScript errors from content scripts.
  • For popup errors, right-click the extension icon in the toolbar and select Inspect popup to open DevTools scoped to the popup.

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Other Chromium browsers

These same steps work in any Chromium-based browser. Look for the equivalent extensions management page in:
  • Brave — brave://extensions
  • Microsoft Edge — edge://extensions
  • Opera — opera://extensions
  • Vivaldi — vivaldi://extensions
Enable Developer mode and use Load unpacked the same way.

Edit & iterate

How to modify files and reload after making changes.

Download

What’s inside your extension ZIP and what each file does.