Duplicates are observations with identical values. The duplicates commands provide a way to report on, give examples of, list, browse, tag, or drop duplicate observations.

duplicates report reports duplicates.

duplicates examples lists one example of the group of the duplicated observations.

duplicates list lists all duplicated observations.

duplicates tag, generate(var) creates a new variable var that gives the number of duplicates of each variable.

duplicates drop keeps only the first of the duplicates and drops the rest.

More examples on the duplicates commands and an alternative method of detecting duplicates:
UCLA: Statistical Consulting Group, How can I detect duplicate observations? | Stata FAQ

Author: Yun Dai, 2018