There’s a persistent myth floating around the research world: if it’s publicly available, it must be free to use however you want. Preprints, sitting openly on servers and indexed by search engines, often fall victim to this assumption. After all, they’re right there, begging to be cited. But as many researchers have learned (sometimes the hard way), there is a crucial difference between “public” and “permitted reuse”. This month’s Researcher Riddle dives into the subtle yet important difference between the two, and how they fit in the world of pre-prints.  

Preprints are preliminary manuscripts shared before peer review, a valuable part of the scientific ecosystem, but not yet validated by external experts. They are generally separated into two categories: public access and permitted reuse. Public access simply means anyone can view a piece of content. No paywall, no login, no institutional affiliation required. On the other hand, permitted reuse is a separate, rights‑based question: it determines whether you can copy, adapt, analyze, redistribute, or build upon that content in your own research. For example, platforms like Research Square publish most preprints under a CC‑BY 4.0 license, which does allow reuse, adaptation, and even commercial use, provided you give proper attribution, link the license, and indicate any changes. Crucially, every preprint receives a DOI, making it a citable part of the scientific record. But not all preprints across all servers share the same licensing terms, and not all data posted publicly is ethically or legally reusable.  

Preprints often feel “free” because they’re openly available, but reuse depends entirely on licensing terms, author permissions, and ethical constraints. Think about it this way: it's like any image you may find online; you can see it for free, but you cannot use it commercially freely. Visibility is not the same as permission, and responsible researchers must check the license, the DOI, and the data provenance before treating publicly accessible material as reusable. Additionally, because preprints are provisional, researchers must treat them with caution: check for updated versions, look for the formally published and peer‑reviewed article, and avoid building critical claims solely on unverified data. With that in mind, let’s step into this month’s scenario. 

You’re a researcher looking to expand the dataset of your manuscript. Which one of these three publicly available sources could you use? 

• A: An internet research paper published as a preprint clearly labeled CC‑BY 4.0, complete with a DOI 

• B: A preprint on a smaller institutional server with no license information listed 

• C: A publicly accessible PDF shared on a lab website, containing raw patient data extracted from social media posts 

• D: A preprint with the CC‑BY 4.0 license, a complete DOI, dated to 2015 

• E: None of them until you can verify peer‑reviewed versions of each manuscript, as none of these papers count as verified datasets. 

The correct answer is A: the internet research paper with the appropriate license. The online study preprint is explicitly published under CC‑BY 4.0, meaning you can reuse, adapt, and build upon the content as long as you provide proper attribution, link the license, and cite the DOI. This is exactly the kind of reuse the license is designed to support. However, one important thing to keep in mind is that having the appropriate license does not automatically mean “ethical”. Especially when it comes to data gathered on the internet, researchers have a responsibility to verify the origin of the data and must be prepared to justify their decisions, document their safeguards, and demonstrate respect for participants' expectations (see Researcher Riddle: Internet data safety for researchers). 

Now let's see why the other options might not be the best choice for you and your manuscript, depending on the questions you are addressing, the rarity of research into this area, and other considerations.  

• B: The small institutional preprint is a tricky one, but not necessarily off-limits. Lack of visible licensing does not automatically prohibit reuse, but it does require caution. You may need to check the server’s policies or contact the authors. Many institutional repositories default to permissive academic reuse, but you must verify before incorporating the data.  

• C: The lab PDF raises a clear ethical red flag. Raw patient data scraped from social media (even if publicly posted) does not make it automatically permissible to use in research. Ethical and legal constraints around consent, privacy, and data provenance make this source unsuitable for reuse (see our previous Researcher Riddle: did they assent to consent?). Public visibility does not override human‑subject protections. 

• D: Even though the preprint dated 2015 has all the necessary permits (license and DOI), it might be a bit too old to be still considered relevant. This all depends on the field of research, but in general it would be best to proceed with caution and verify whether a more recent version has been released.  

• E: Using none of these options because they lack peer review misunderstands the role of preprints. You should treat them cautiously, but you don’t need to wait for peer review to reuse content that is properly licensed and cited. 

If you’re navigating the world of preprints, whether mining data, building analyses, or simply staying informed, make sure you understand the difference between public access and permitted reuse. 

Licensing matters. Attribution matters. Ethical data handling matters even more.