Field experiments are carried out in the everyday, real-life environment of the participants. As in lab experiments the researcher manipulates the independent variable but the:

• Setting
• participants
• manipulations / treatments
• outcome measures

are all authentic

• Randomized experiment in a real-word setting
  
• Results are generalizable to real-world behavior
• Participant are unaware taht they are taking part in a study and are unaware of the different manipulations
• Often requires to work together with an organization
• Tranditional (offline) field experiments v.s. Large-scale (online) field experiments

• When the number of independent (and moderator) variables is limited and when they can be manipulated
  
• When it is important to measure real-world behaviro in real-world situations (high external validity is curcial)
• When you want to capture second-order and long-term effects of your manipulations