Which records did Tacitus use to write about Roman emperors?

To write his accounts of Roman emperors, the historian Tacitus utilized a variety of sources, ranging from earlier historical works to official government documentation and personal accounts.1

Historical and Literary Sources

For the period spanning from Augustus to Vespasian, Tacitus relied on the writings of predecessors who had already compiled material from public records and contemporary commentary. Key historians he consulted included:1
* Aufidius Bassus and Pliny the Elder: Their works covered the early empire and the German wars.12
* Specific Period Authorities: He drew upon Servilius Nonianus for information on Tiberius, Cluvius Rufus and Fabius Rusticus for the reign of Nero, and Vipstanus Messalla for the events of the year 69.1

Official and Personal Records

Tacitus also consulted primary documentation and firsthand accounts when necessary, including:
* Official Records: He accessed the Senate’s records and the official daily journal. For the later years of Vespasian and the reigns of Titus and Domitian, he relied more heavily on official reports.1
* Firsthand Information: He utilized personal memoirs, such as those of Agrippina the Younger and the military memoirs of the general Gnaeus Domitius Corbulo, as well as specific documents like a speech delivered by the emperor Claudius.1