Abstract: There is provided herein a technical solution to the technical problem of being able to obtain proof-of-play and display timing data despite not being able to access or modify the display controller software of digital display devices of outdoor advertising networks which entails transmitting hypertext marked-up image display data files to digital displays which comprise client-side code and a resource locator. As such, when each display data file is displayed by the digital display the web-capable display controller thereof executes the client-side code to transmit proof-of-play tracking data to the resource locator and which may periodically transmit timing data until the instantiation of the client-side code is destroyed by the display controller. Aspects are also provided herein for being able to achieve sub second resolution and account for data transmission errors.