
Test WebExtensions with Chrome Web Store. Till now you can not install Chrome extensions in Firefox and Firefox extensions in Google Chrome, the latter is not possible, but the former is possible now, thanks to WebExtensions!
Currently WebExtensions API is work in a progress, when Mozilla completes the API, you can able to install extensions in Chrome Web Store in Firefox without any issues.
While the Firefox browser vendor is working on it, a developer has created Chrome Store Foxified add-on –more useful for add-on developers than to general users who want to port to their extension to Chrome–, which enables Chrome Web Store and makes point and click to install Chrome extensions in Firefox 48+ browser.
Note: Experimental WebExtensions support is already available and enabled in Nightly.
Update: The developer has updated the extension with Firefox 57+ compatibility and added Opera Store support as well, means with Chrome Store Foxified installed in Firefox, you can install extensions from Opera add-ons site also.
Installing Chrome Extensions in Firefox
1. Install Chrome Store Foxified add-on, visit Chrome Web Store in Firefox, select ‘Extensions’ section (you don’t need to sign into Google account)
2. Find an extension and visit its page, you can see ‘Add to Firefox‘ button, when you click the button the add-on fetches the Chrome extension data and converts into Firefox format and offers multiple options:

Sign add-on then install
Note: The add-on itself will automatically sign the add-on, you need to have a valid Firefox account and signed into addons.Mozilla.org to install the extension normally.
Just sign and download
Install temporarily: Clicking this means the extension will be unsigned and will be installed temporarily in Firefox for that session, when you restart browser, it will be removed.
For the extension to be signed by the add-on, you need to accept to the agreement, the process of signing and installing the Chrome extension normally is a complex one and has’t worked for us, at least you can able to install Chrome extensions in Firefox temporarily. This extension has made that possible.