A code-generating system can be accessed from within a messaging application on a mobile computing device to generate and insert a two-dimensional (2-D) code into a message. During operation, the system can receive a request to generate a 2-D code, such as from the messaging application executing on the mobile device or from the operating system. In response to receiving the request, the system can present a user-interface (UI) mechanism (e.g., modal window) for entering or selecting message content to convert into a 2-D code. Then, in response to obtaining the message content from a local user, the system may generate a 2-D code for the message content, and may generate a message that includes the 2-D code (e.g., by inserting the 2-D code into the message body). The system may then send the message, which includes the 2-D code, to a target recipient.