Does RCS use data or Wi-Fi?

This is the single structural difference from which almost everything else about RCS follows. SMS was designed in the 1980s to squeeze 160 characters into spare capacity on the carrier's control channel. It works nearly everywhere and costs almost nothing to carry, but that tiny envelope is why SMS cannot do rich media, branding, or engagement signals. RCS moved business messaging onto the internet, where those constraints do not exist.

Which connection it actually uses

Whichever one the phone has. On Wi-Fi, RCS uses Wi-Fi. On mobile data, it uses the data plan. The messaging app switches between them the same way any other app does, and the recipient sees no difference. A phone in airplane mode with Wi-Fi switched back on can still send and receive RCS, which is a common source of surprise for people used to SMS behaviour.

How much data an RCS message consumes

For text, the answer is negligible. A plain RCS text message is a few kilobytes, so a year of them would not register against any modern data plan. What consumes data is media: an RCS image, GIF, or video is a real file transfer, and rich media is where the difference becomes measurable.

Google's RCS for Business platform caps the whole message payload at 250 KB and individual media files at 100 MB, though real campaign images are far smaller. Compressing images properly is worth doing anyway, because a heavy image loads slowly on a weak connection, and a slow-loading card is one people scroll past.

What happens with no data at all

Nothing breaks. Before delivering, the platform runs a capability check on each destination number, and a recipient who cannot receive RCS gets the same message as SMS or MMS instead. That per-recipient fallback is automatic and invisible to both sides, and it is what makes an RCS-first programme safe to run before every customer is RCS-ready. How RCS falls back to SMS covers the mechanics.

For a business the practical consequence is that connectivity is not a reason to delay adopting RCS. Recipients on a strong connection get the rich version, recipients with no data get a clean SMS, and your billing reflects what was actually delivered rather than what you hoped to send.

Does it cost the recipient anything?

Not the way a text message does. RCS messages do not draw on SMS allowances or per-message charges on the recipient's plan, because they are not delivered as texts. They use data, which on the great majority of US plans is either unlimited or generous enough that messaging is not a meaningful line item. Recipients on a strictly metered plan, or roaming internationally without a data package, are the exception worth knowing about.

For the sender the economics are different again, and are set by your provider and Google's RBM fees rather than by data. How much does RCS cost sets out the actual numbers.