Does the QR code expire?

Never: it holds the address or text itself, with no redirect service in between. It works for as long as its content does.

Which error correction should I pick?

Medium suits almost everything. High survives a damaged or partly covered code (by a logo, say), at the cost of a denser code.

Guests scan it and join the network without typing the password. The password stays in your browser — it isn’t sent anywhere.

No. The code is worked out in your browser; nothing is uploaded or stored.

A QR code for a website, a Wi-Fi network, a contact, an email or a place — as PNG, SVG or vector PDF, in your colours.

Does the QR code expire?: Never: it holds the address or text itself, with no redirect service in between. It works for as long as its content does.
Which error correction should I pick?: Medium suits almost everything. High survives a damaged or partly covered code (by a logo, say), at the cost of a denser code.
How does the Wi-Fi code work?: Guests scan it and join the network without typing the password. The password stays in your browser — it isn’t sent anywhere.
Is my data sent anywhere?: No. The code is worked out in your browser; nothing is uploaded or stored.