Secondary data is the data that has been collected in the past by someone else but made available for others to use. They are usually once primary data but become secondary when used by a third party.

Secondary data are usually easily accessible to researchers and individuals because they are mostly shared publicly. This, however, means that the data are usually general and not tailored specifically to meet the researcher's needs as primary data does.

In a time when data is becoming easily accessible to researchers all over the world, the practicality of utilizing secondary data for research is becoming more prevalent, same as its questionable authenticity when compared with primary data.