Primary vs. Secondary Sources: A Guide
In academic research and credible writing in general, it’s preferred to obtain your information from the original — or primary — source. That’s because primary sources provide direct evidence about the research or item being studied, making them especially useful for establishing credibility and authority.
It’s not always desirable or possible to use and/or cite the primary source for your research for a variety of reasons, which we’ll discuss. Secondary sources can be more useful when your research needs explanation or expert insight rather than direct evidence alone.
If it’s been some time since you’ve written a paper for school and you need to brush up on your primary and secondary sources, this is the guide for you.
What Is a Primary Source?
Primary and secondary sources differ in how close they are to original information.
A primary source provides direct, firsthand evidence about a topic. It may have been created by someone who experienced or witnessed an event, or it may present original research or data.
The Library of Congress describes primary sources as “original documents and objects that were created at the time under study.”
Examples of Primary Sources by Discipline
- History: diaries, speeches, letters, maps, government documents, photographs, artifacts
- Social sciences: survey data, census records, interviews, original empirical research, lab notebooks
- Literature and arts: original texts, films, paintings, sculptures, poems, plays
- Scientific research: raw data, publications in peer-reviewed journals with methods and results, presentations or papers given at scientific meetings detailing new research
What Is a Secondary Source?
A secondary source is one step removed from the original information. Secondary sources interpret, analyze, or evaluate primary sources and may include summaries or paraphrases to help explain the original evidence.
A secondary source helps contextualize or give commentary on the evidence provided by primary sources.
Examples of Secondary Sources
Examples of secondary sources across disciplines include:
- Textbooks
- Scholarly articles that review research
- Review articles
- Biographies
- Academic monographs
- Literary criticism
A note: Not all books or articles are secondary sources. Some are primary, depending on use and context. If you’re unsure and it’s for a school paper, your safest bet is to ask your instructor if the source is acceptable. You can also check with your school library.
Primary vs. Secondary vs. Tertiary Sources
Tertiary sources repackage information once again. They may index, organize, compile, or provide condensed versions of other sources.
Tertiary sources are often tools that help researchers locate, organize, and understand information. Examples include reference materials such as dictionaries, encyclopedias, bibliographies, almanacs, and library catalogs.
In Short:
Primary sources offer original, firsthand evidence — think interviews, original data/research, and artifacts. They’re the best for credibility purposes because you are, quite literally, going right to the source.
Secondary sources report on the primary information above. An online magazine giving its analysis of a new theory or commentary on the latest State of the Union address would be a secondary source.
Tertiary sources summarize or organize other sources. Think of a bibliography or a library catalog.
Does APA Style Require Primary Sources Only?
APA Style is the standard style for academic writing (including work done at Purdue Global). APA guidelines recommend citing primary sources when possible and secondary sources sparingly.
“It is important — and ethically necessary — to provide full credit to the creators and publishers of documents, and to allow future scholars to find the source quickly and correctly,” the Library of Congress states.
You can cite a secondary source if, according to APA, the source is credible and appropriate for your research. APA Style uses the author–date citation system, in which a brief in-text citation directs readers to a full reference list entry.
>>Related Reading: How to Format Papers Using APA
When to Use a Primary vs. a Secondary Source
There may be times when you want to cite a secondary source; it depends on the purpose of your paper and the point you are trying to make. Follow these guidelines, keeping in mind that for academic writing, primary sources are preferred:
Primary sources strengthen original arguments and evidence. If your goal is to report a statistic, original idea, or raw data, use the primary source in the citation.
Secondary sources offer context and scholarly conversation. If you’re writing about the analysis of the primary information, credit it to the appropriate secondary source.
Sometimes, primary sources aren’t available to cite. In that case, aim to find a scholarly journal or reputable source that conveys the same data.
How to Find Primary Sources
When looking for primary sources for academic writing, check:
- Public and university library catalogs
- Special collections, archives, and government databases
- Digital archives, institutional repositories, and historical databases
- Open-access collections from national libraries or public records
When searching for sources digitally, include terms such as “original research articles” or “datasets” in academic databases. Remember, you’re looking for authenticity and relevance. The Library of Congress publishes sets of primary sources on specific topics that can assist you in your search.
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