Note: Instructors, departments, and disciplines define 'primary sources' differently. Contact your instructor if you are unclear about what counts as a primary source for an assignment! This guide only serves as one possible starting place.
With that being said, primary sources are generally understood to...
...provide first-hand testimony, direct evidence, or original findings concerning a topic under investigation. They are created by witnesses or recorders who experienced the events or conditions being documented.
Often these sources are created at the time when the events or conditions are occurring, but primary sources can also include autobiographies, memoirs, oral histories, and scientific research articles recorded later.
Primary sources are characterized by their content, regardless of whether they are available in original format, in microfilm/microfiche, in digital format, or in published format. --based on Yale's Primary Sources LibGuide Module