Transacting without the internet.
WHAT USSD IS
A session-based protocol on mobile networks, using short codes and menus.
WHY IT MATTERS HERE
It works on any phone, without data, and reaches customers smartphones do not.
WHAT IT IS USED FOR
Balance enquiry Transfers Airtime and bill purchase Merchant payment
WHAT CONSTRAINS IT
Short session timeouts Limited characters per screen No graphics Session loss on network interruption
WHAT THAT MEANS FOR DESIGN
Few options per screen Short, unambiguous text Minimal steps to completion State preserved so an interrupted session can resume
WHY RESUMPTION MATTERS
Sessions drop routinely, and restarting from the beginning causes abandonment.
WHAT THE COST MODEL IS
Charged per session, usually to the customer.
WHY THAT MATTERS
Long flows cost the customer money, and they notice.
WHAT SECURITY CONSIDERATIONS APPLY
The channel is not encrypted end to end Codes entered may be observed SIM swap enables account takeover
WHAT TO IMPLEMENT
Transaction limits Verification for higher-value actions Detection of recent SIM changes
