With the new iOS and iPadOS 15, Apple has enabled extensions in Safari. These are typically utilities that can do one or two small things that positively affect your web browsing experience. Things like better password management, universal dark mode, and easy coupon finding are some examples.
There are a couple of ways to install Safari extensions for iOS and iPadOS 15. First, you can go to the Settings app, select Safari, and inside the Extensions section, turn on any extensions you’ve installed and give them permission to interact with webpages. Second, you can enable or disable extensions by tapping on the puzzle piece icon in the address bar and then choosing ‘Manage Extensions.’
I think John Voorhees at MacStories did a great job at sorting through and picking some of the best ones currently available.