To protect users and ensure their safety while browsing the web, Google Chrome will no longer allow extensions to be installed from developers’ websites. They can only be installed from the Chrome Web Store.
Google Chrome will no longer allow you to install extensions from websites
For the developers, the Google team decided to implement this change in different stages. To begin with, new extensions can only be installed through the Chrome Store, so developers will no longer be able to enable the installation from their web pages.
On the other hand, the external extensions that have already been published will have a margin of 3 months to update the dynamics. As of September 12, the stand-alone extension installation will be blocked.
If a user tries to install an extension using that dynamic, they will automatically be redirected to Google Chrome to complete the process. And as of December, with the arrival of version 71 of the browser, the API that allows developers to offer the installation of its extension independently will be completely eliminated.
The idea is that Chrome Web Store gives users more security about the extensions they can install, giving them all the information they need to understand the permissions they grant or the dynamics they plan to implement.
This link mentions some of the steps that developers should take into account to update the installation dynamics of their extensions.