Glossary
What is SMS gateway?
An SMS gateway is the software or service that turns a request from a computer system into a text on the mobile network and passes replies back.
The word gets used for two things. Sometimes it means a whole service with an API, as in 'SMS gateway API'. Sometimes it's a box with a SIM card in it that sends texts the way a phone would. Either way its job is to get a message out of software and onto a network, and to bring back whatever the network says about it.
The usual set-up looks like a Southampton gym whose booking software calls a gateway's API: the software decides who gets which text and when, and the gateway handles the sending.
From your side, CaptiFi Connect is the gateway. You call one REST API or use the dashboard, and the platform decides how each text travels, from a UK mobile number or through a licensed aggregator. You get the same statuses and webhooks whichever way it goes.