A web browser extension is a downloadable add-on that can aid your browsing of the web. Some are 3rd party whilst others are from established developers, their uses are subject to the user’s wishes.
For example, a web browser extension like Grammarly helps the user to detect and correct spelling and grammar mistakes by reading in real time. Whereas a web browser extension like Honey actively searches for codes you can use in order to get money off from e-commerce websites.