Determining a duration content is visible to a user of an online system

A method comprising:

• including instructions in a page of content that, when executed by a client device presenting the page of content, cause the client device to:
• obtain a visibility state of an application presenting the page of content, the visibility state indicating whether at least a threshold amount of the page of content is presented on a display device of the client device,
• obtain a time when the visibility state was obtained,
• obtain one or more updated visibility states of the application presenting the page of content,
• obtain one or more times when each of the one or more updated visibility states were obtained, and
• generate an identifier corresponding to execution of the instructions by the client device;
• receiving the visibility state and the time when the visibility state was obtained in association with the identifier;
• receiving the one or more updated visibility states and the one or more times when each of the one or more updated visibility states were obtained in association with the identifier;
• and
• determining a duration the page of content was presented based on the visibility state, the time when the visibility state was obtained, the one or more updated visibility states, and the one or more times when each of the updated visibility states were obtained.

A computer program product comprising a computer readable storage medium having instructions encoded thereon that, when executed by a processor, cause the processor to:

• include additional instructions in a page of content that, when executed by a client device presenting the page of content, cause the client device to:
• obtain a visibility state of an application presenting the page of content, the visibility state indicating whether at least a threshold amount of the page of content is presented on a display device of the client device,
• obtain a time when the visibility state was obtained,
• obtain one or more updated visibility states of the application presenting the page of content,
• obtain one or more times when each of the one or more updated visibility states were obtained, and
• generate an identifier corresponding to execution of the instructions by the client device;
• receive the visibility state and the time when the visibility state was obtained in association with the identifier;
• receive the one or more updated visibility states and the one or more times when each of the one or more updated visibility states were obtained in association with the identifier;
• and
• determine a duration the page of content was presented based on the visibility state, the time when the visibility state was obtained, the one or more updated visibility states, and the one or more times when each of the updated visibility states were obtained.