Click-to-chat is an entry point, a link, a button, an ad or a QR code, that opens a messaging conversation with a business in the customer's messaging app with one tap.
How it starts a conversation
The link or code opens the phone's messaging app addressed to the business, often with a pre-filled first message such as "Hi, I'd like to book". The customer sends it, and that first mobile originated message is both the opening of the thread and, if the pre-filled text is a clear opt-in, the consent record. From there the business replies over RCS if the handset supports it, with a verified sender, rich cards and suggested replies, or over SMS if it does not.
Where it is used
On a website's contact page instead of a form, on packaging and in-store signage as a QR code, in a "text us" line in an email, and in ads that resolve to a conversation rather than a landing page. It suits questions that are quicker to answer in a thread than on a page, and it is how an RCS chatbot gets its first message.
What to get right
The pre-filled message must say what the customer is agreeing to, the business must reply from a sender it is allowed to use, and the QR code should point at the same number everywhere. A QR opt-in counts as consent only if the disclosure is next to the code.