Reliability is how accurate and trustworthy a source is. Historians check where information comes from to decide if it can be trusted. Sources based on direct evidence are often considered more reliable.

A diary written at the time of an event may be more reliable than a story told many years later. Official records, photographs, and eyewitness accounts are often examined closely. Errors or missing details can affect reliability.

Researchers compare multiple sources to check accuracy. Reliable sources are important for building clear and supported accounts of history.