Here is a thing worth knowing about the free QR generators on the internet: a lot of them do not encode your link. They encode a link to their site, which then redirects. That is convenient right up until the service shuts down or starts charging, and every printed poster you made is dead.
Codes generated here contain your actual data. Nothing to expire, nothing to subscribe to, no redirect in the middle.
There are seven content types, and the ones beyond a plain link are the interesting ones. A Wi-Fi code that joins the network without anybody typing a password. A contact card that lands in the phone book in one tap. Email, phone, SMS and plain text as well.
Styling is where it stops being a utility and starts being design. Code color and background, transparent background if you want it on a photograph, square, rounded or dotted modules, separate styling for the three corner eyes, and a logo in the middle taken straight from your brand kit. It arrives as a layer, so it can sit inside a real design rather than next to one.