A diary study requires users, or observers of users, to keep track of activities or events in some form of diary or log for a particular period of time.
Participants or observers may be asked to track specific items like mobile device usage, use of personal calendars, and course work or general activities like "what you did for each 30 minutes of your work day." Diary entries can include: text accounts of events, pictures, video, audio, sketches, and voice-mail.
The main benefit of a diary study is to get information about the user's experience over time. The feedback is also often provided while the user is interacting with the product, so there is less of a lag in the feedback than with other methods and it is in the actual context of use. The main disadvantage is that all information is self-reported.