1. Data source and retrieval
PaperTracer uses data from OpenAlex, a free and open catalog of the world's scholarly knowledge. When you search for a paper, we retrieve its metadata including authors, publication date, and citations using the OpenAlex API.
2. References and citing works
A reference is a paper that your query paper cites. A citing work is a paper that cites your query paper. Together, they form the citation neighborhood around your paper.
3. Links between works
Links in the graph are induced from OpenAlex's reference lists. When we retrieve a set of papers, we examine their references and draw edges between any two papers that both appear in your neighborhood. Links are not shown between papers that were not fetched together in the same query.
After you expand a paper, the app asks OpenAlex for the reference lists of up to 400 of the works now on display, choosing those with the most citations and always keeping the root and the expanded papers, and draws every citation among them. A paper reached through one expansion is therefore linked to a paper reached through another whenever OpenAlex records that citation. If this request fails, the links from each individual query remain and a note says that some links between expanded papers could not be loaded.
4. Timeline view
Horizontal position is publication date. Vertical position only separates papers.
In the Timeline view, papers are positioned on a horizontal axis according to their publication year. The vertical axis is determined by a force-directed layout to minimize overlap. The root paper is fixed at its publication date and at vertical center (y = 0). References appear to the left; citing works appear to the right.
5. Similarity view
Papers that cite each other, or share many neighbors, sit closer together.
In the Similarity view, papers are arranged using a force-directed layout based on their citation links. The root paper is pinned at the center. This layout emphasizes direct connections and clusters of related work.
6. Co-cited view
Papers frequently cited together with the root sit closer together.
The Co-cited view shows papers that are frequently cited together with your query paper. We sample up to 200 citing works, find the top 50 most frequently co-cited papers, and draw edges between papers with a Jaccard similarity above 0.25. Each paper retains its three strongest edges to keep the graph readable.
7. Size and color encodings
Node size (radius) is proportional to citation count: more cited papers appear larger. Color represents publication decade using a five-bin sequential ramp: papers from the 2020s are the brightest; older papers are progressively darker. Papers with unknown publication years appear as hollow rings.
8. Known data issues
OpenAlex provides reliable metadata but has known limitations:
- Record merging:OpenAlex sometimes merges records for the same work. A work's title, DOI, or publication year can come from a different version or a different work. For example, the OpenAlex record for “Attention Is All You Need” (W2626778328) shows a publication date of 2025-08-23, although the paper appeared in 2017.
- Incomplete references: Reference lists can be incomplete for very recent papers or for records that have been newly re-indexed.
- Year correction scope:When a paper's publication year is missing, we can infer it from its arXiv identifier if available. Year correction only applies in these cases; we do not otherwise estimate or modify publication dates.
- Earliest-citation placement: For the paper at the center of a neighborhood that has at least 20 citations, we look at the five earliest works that cite it. If OpenAlex dates the paper at least three years later than the fifth of those, the paper is shown in that earlier year instead, unless the references we retrieved are mostly dated later than that year, in which case the reported year is kept and a note says the dates look inconsistent. The change is never silent: it is stated in the data notes, and other papers are not adjusted this way.
- No silent edits: The app never modifies or silently corrects data. Any correction made is recorded in the annotation export and shown in the interface.
9. How to cite
If you use PaperTracer in your research, please cite it as:
PaperTracer, accessed 10/5/2026. Data from OpenAlex.