If you’re a developer, to view the source code of the extensions you’ve to download some chrome extensions, or you want to install an extension manually via developer mode where installing that from Chrome Web Store is failed, in both cases you need to download Chrome extension manually, which Google is not allowing us after the launch of their Web Store, Google WebStore Downloader is a Firefox add-on which lets you download Chrome extensions from Chrome WebStore easily.
One thing lot of users do know is that when you visit Chrome WebStore in Firefox, the page asks to download Chrome to install apps, extensions and themes, but with the install of Google WebStore Downloader extension “Download” button appears after “Add to Chrome” button in Firefox, which is shown below in the screenshot.
Update Novermber 7, 2014: This Extension is no longer working.
You can easily download any extension and change its extension to Zip type and load unpacked extension by selecting ‘developer mode’ in Chrome.
Till now Chrome extension is saved as HTM file which you can overcome by using above said extension.