Rulers is a historical reference resource documenting political leadership around the world. Its lists cover heads of state and heads of government, as well as selected de facto leaders, across countries and territories, with records reaching back to about 1700 in most cases. The site also includes information on subdivisions within some countries, selected international organizations, foreign ministers worldwide, and other government ministers for certain countries.

Entries provide office-holding dates and, where available, birth and death years. The resource explains how uncertain dates are marked and cautions that biographical details may vary between sources. An extensive alphabetical index contains more than 50,000 entries, including full and alternative names, other positions, and further biographical information; many of its larger biographies link directly from the leadership lists. Users can explore country and organization listings, a clickable map, religious leaders, and a chronology of relevant events from 1996 onward. The site is designed as a structured historical and biographical guide for researching political officeholders, government roles, and leadership changes across countries and territories.