Starting today, Google Chrome users on Windows will only be able to install extensions from Google Web Store only. This step has been taken to make Chrome more secure. Because most of the times, third party malicious browser extension change the browser settings and cause problem.
Users who have already installed extensions from third-party website will find all those extensions disabled. These extensions cannot be re-enabled or re-installed again. The only way to install those extensions is to get those extensions from Web Store.
Google first announced this plan last November and suggested all developers to move their extensions on Web Store.
For developers, local install will work. So, developers will be able to check their extensions by local installation.
This move will protect users from malicious browser extensions which change homepage and other browser settings. Many browser extensions also inject ads in the websites you browse. If your browser seems to be hijacked and settings changed suddenly, you can fix it by resetting it and disable all unknown extensions.