Here is a 1-paragraph summary of the text: QR codes have made a comeback during COVID and can be used to seamlessly onboard customers into an SMS campaign or other communication channels like WhatsApp, phone calls, and email. QR codes for SMS work by decoding a set of characters and words that translate to a message body pre-populated in the SMS app. With Twilio, users can generate QR codes for different communication channels using a 3-step process: configure their number, generate a QR code, and add it to signs or billboards. The QR code can be linked to a keyword that determines how to respond, making it useful for applications like customer feedback or surveys. Additionally, users can bulk generate QR codes using Google Spreadsheets or an open-source command line tool like qrencode.