Installing browser extensions can add extra security and functionality to your browser. But use caution! Some extensions are bundled with other software that you don't actually want. You could inadvertently download an extension that compromises your browser security.
When considering browser extensions, make sure they are approved by the browser you're trying to add them to. A good way to make sure is to download them through the official pages from each browser:
HTTPS Everywhere will tell your browser to automatically connect to the encrypted version of a site (https) instead of the regular site (http) if an encrypted version is available.
Ghostery tells you who is tracking your activity and why on any given web page. It also gives you the option to block those trackers from gathering information about you.
Privacy Badger identifies trackers that follow you from site to site, and blocks them from gathering your information. It also blocks ads. You can choose what trackers to allow or block on any given page.
UBlock Origin is an extension that allows for flexibility in what is blocked or allowed. Users can choose different 'lists' to block ads, trackers, malware, and many other unwanted web features.
The search engine DuckDuckGo doesn't track your search activity as you use it; this extension lets you use DuckDuckGo in the search toolbar of your browser, from a right-click menu, or from a toolbar button.