What is an SMS gateway?

Short answerAn SMS gateway is the service that converts a message from an application into a format mobile networks can deliver, and passes it to the right operator. It is what lets software send a text without a phone or a SIM card, and it reports back whether the message was delivered.

How does an SMS gateway actually work?

Your application makes an authenticated request — usually an HTTPS call, sometimes an SMPP session — containing the recipient's number, the message text and a sender ID. The gateway validates it, works out which mobile operator owns that number, converts the message into the protocol that operator's network speaks, and hands it over.

The operator delivers to the handset and returns a delivery receipt. The gateway passes that back to you, normally by calling a webhook you host, so your system knows the outcome of every message individually.

Why not connect to mobile operators directly?

Because there are more than a thousand of them, each with its own commercial agreement, technical connection, registration process and content rules. A gateway maintains those relationships once so every customer can use them.

The difference between gateways is mostly the quality of those connections. A direct connection to an operator delivers faster and reports more accurately than a route resold through two or three intermediaries — and resold routes are where most unexplained delivery failures come from.

What should you look for in an SMS gateway?

• Direct operator connections in the markets you actually send to, rather than an aggregate global figure.
• Real delivery receipts — a per-message status with a timestamp and a failure reason, not just 'submitted'.
• Sender ID registration handled for you, because in most countries unregistered traffic is blocked.
• Throughput that matches your peaks, not your average.
• Fallback to other channels, so a failed SMS is not simply a failed message.