What is USSD? A Complete Guide to USSD Technology (2026)

If you've ever dialed *170# to check a mobile money balance, or *123# to buy airtime, you've used USSD — quite possibly the single most-used piece of financial technology on the African continent, despite being older than the smartphone.

This guide covers what USSD actually is, how it works under the hood, and why it remains the default channel for mobile money and banking across markets where internet access still isn't universal.

---

1. What is USSD?

USSD (Unstructured Supplementary Service Data) is a communication protocol built into the GSM mobile network standard that lets a phone exchange short messages with an application in real time, over the same signaling channel used for calls — not over the internet.

When you dial a USSD code like *123#, your phone opens a live session with a server, which responds with a text menu you navigate by typing numbers. Unlike SMS, which sends and receives standalone messages, a USSD session is a continuous back-and-forth conversation that stays open until the user finishes or it times out.

---

2. Why USSD Still Matters in 2026

Three properties explain why USSD has outlasted multiple generations of "the next big thing" in mobile:

It works without internet or a smartphone

USSD runs over the GSM signaling channel, the same one used for voice calls — it needs no data connection and works on the most basic feature phone ever sold. In markets where mobile data is expensive or coverage is patchy, this alone makes USSD the only channel that reliably reaches everyone.

It's session-based and instant

Unlike SMS, a USSD session is live and interactive — the user sees a menu, picks an option, and gets an immediate response, all within a single continuous session. That real-time back-and-forth is what makes USSD suitable for things SMS can't do well, like multi-step transactions.

It's the backbone of mobile money

Mobile money services across Africa are built on USSD precisely because it reaches every phone, requires no app install, and completes transactions in seconds. For a huge share of the population, USSD banking menus are their primary banking interface.

---

3. How a USSD Session Actually Works

1. User dials a short code — e.g., *384*1#.
2. The carrier routes the session to whichever server is registered for that short code — your application's USSD gateway.
3. Your server responds with a menu, marked as still-active (see CON vs END below).
4. The user selects an option, which gets sent back to your server as the next request in the same session.
5. The session continues — menu after menu — until your application sends a final response, or the session times out (typically 60–120 seconds of inactivity).

[ User dials *384*1# ]
        │
        ▼
[ Carrier routes session to your USSD gateway ]
        │
        ▼
[ Your server responds with menu: "CON Welcome. 1. Balance 2. Transfer" ]
        │
        ▼
[ User selects "1" ]
        │
        ▼
[ Your server responds: "END Your balance is GHS 500.00" ]

---

4. CON vs END: The Two Response Types

Every response your application sends back has to be prefixed with one of two keywords, and this single detail is what makes a USSD menu actually navigable:

• CON — "continue": the session stays open and the carrier displays your message, waiting for further input.
• END — the session terminates after displaying your message; no more input is expected.

Get this wrong — send END when you meant CON — and the user's session closes after step one, no matter how many menu levels you built.

---

5. USSD vs SMS: What's the Difference?

These two get confused constantly since both work on any phone without data:

In practice, most fintech products use both: USSD for the live transaction (checking balance, sending money), SMS for the confirmation receipt afterward.

---

6. Common USSD Use Cases

• Mobile money — balance checks, transfers, airtime and bill payments
• Banking — account access and transactions for users without a banking app
• Customer self-service — account management, support ticket creation
• Agriculture — market price lookups, weather updates for farmers without smartphones
• Elections and surveys — reaching respondents at population scale regardless of device
• Healthcare — appointment booking and health information access

---

7. Building Your First USSD Menu

Here's a minimal webhook handler showing the actual request/response shape a USSD gateway sends:

import express from "express";
const app = express();
app.use(express.urlencoded({ extended: true }));

app.post("/ussd", (req, res) => {
  const { sessionId, serviceCode, phoneNumber, text } = req.body;

  let response = "";

  if (text === "") {
    // First request in the session — show the main menu
    response = `CON Welcome to Sendexa Demo
1. Check Balance
2. Send Money`;
  } else if (text === "1") {
    response = `END Your balance is GHS 500.00`;
  } else if (text === "2") {
    response = `CON Enter amount to send:`;
  } else if (text.startsWith("2*")) {
    const amount = text.split("*")[1];
    response = `END GHS ${amount} has been sent.`;
  } else {
    response = `END Invalid option.`;
  }

  res.set("Content-Type", "text/plain");
  res.status(200).send(response);
});

app.listen(3000, () => console.log("USSD service listening on port 3000"));

text accumulates the user's choices across the session, separated by * — that's how a stateless webhook can still track a multi-step menu without a database, for simple flows. For anything beyond a couple of levels, you'll want to persist session state server-side rather than parsing an ever-growing text string.

For a full walkthrough of getting a short code, going live, and handling session state properly, see our step-by-step USSD build tutorial.

---

Conclusion

USSD isn't legacy technology being kept alive out of nostalgia — it's the only channel that reliably reaches every phone on the network, with zero dependency on internet access or app installs, and near-instant response times. For any product that needs to reach users beyond the smartphone-and-data-plan segment — which, across most of Africa, is still the majority — USSD is not optional infrastructure.

Sendexa provides USSD gateway access with direct connections to major carriers, short code provisioning, session management, and mobile money integration, so you can focus on the menu logic instead of the carrier plumbing.