What is USSD (Unstructured Supplementary Service Data)?

What to know about this communications technology

Unstructured Supplementary Service Data (USSD) is a communication protocol for mobile phones. By using USSD codes, you can access web-based services without installing a mobile app. Here's what is it, how it works, and why it's important.

What Is USSD?

The USSD messaging protocol is part of the Global System for Mobile Communications (GSM) digital cellular standard. Like SMS and MMS, USSD facilitates communication without the need for a dedicated app. Unlike SMS, which is used for back-and-forth text messaging between two phones, USSD establishes a real-time connection between your phone and a mobile network or a server. That way, you can do things like add time to your phone plan, check your bank account, and more without having to download or install any apps on your device.

What Is a USSD Code?

USSD relies on codes made up of characters found on every mobile phone. When you dial a USSD code, your phone sends a request to a USSD network gateway, which routes the request to a web-based application. The network gateway then returns a text-based menu that you can use to interact with the app.

On prepaid phones, for example, you can use USSD codes to check your remaining balance, enable roaming, or use location-based services. It's also possible to get social media updates from Facebook and Twitter via USSD. USSD codes can be used to transfer money, set up call forwarding, and even browse the web via Wireless Application Protocol (WAP).

Running USSD Codes

Most USSD codes begin with an asterisk (*) or a hashtag (#). To initiate a USSD request, enter the USSD code on your keypad. Some codes will run immediately while some require you to tap Send.

Since USSD applications run on your mobile network rather than the device itself, they don't take up storage space or consume system resources, making them especially useful for older phones. No internet connection is required to use USSD apps; as long as you can connect to your mobile carrier's network, you can take advantage of USSD codes.

Feature Codes

You don't need a smartphone to use USSD codes; however, some codes are exclusive to specific types of phones. Also called quick codes or feature codes, these USSD codes are programmed into the device's SIM card.

Some feature codes only serve one purpose. For example, dialing *#06# on most Android phones will display your IMEI number. On iPhones, dialing *3001#12345#* with display information about your device and SIM card. Other codes are specific to your mobile carrier. For example, on T-Mobile phones, you can turn on call forwarding with the code *43#.

Other Uses for USSD

USSD codes allow companies to provide web-based services to users. Businesses can develop USSD-based apps to do things like:

  • Solicit feedback from customers
  • Request a callback
  • Confirm delivery orders
  • Send virtual coupons

Making Payments With USSD

Some banks and online payment services support balance inquiries and money transfers via USSD, which is more convenient than using a mobile app. You must first register your phone number with a payment method, then dial *99# to set up mobile payments.

When you dial *99# again, you'll have the option to send money directly to another mobile user. For example, if they have USSD payments set up on their phone, you can send or request money by entering their phone number.

USSD payments are more common outside of the U.S., particularly in parts of the world where internet connections are unreliable. The only major downside is that USSD codes do not work on all phones, but they are still more accessible than mobile apps designed for smartphones.

USSD, MSS, and SMS

USSD is often used in conjunction with SMS and MSS. For instance, when you purchase digital goods via USSD payment, they can be delivered via MSS, and you might receive a receipt via SMS.