API costs per paper
Variable definitions (first 8 pages โ AI)
~$0.001
Each citation hover
~$0.0002
Typical session (paper + 20 citation hovers)
~$0.005
Don't worry, it's on me ๐
Variable Detection
When you upload a PDF, var scans every page and computes the dominant body font. Any single letter rendered in a different font (typically a math italic or symbol font) is flagged as a candidate variable. Greek letters (ฯ, ฮฒ, ฯโฆ) are always detected regardless of font. Subscripts are identified geometrically โ a smaller glyph sitting to the right and below a base letter is merged in as a subscripted variant (e.g. Yit). Variables with the same base letter share a color family; different subscripts get different shades.
โ Limitation: Image-Based Equations
Some publisher PDFs (Elsevier, Springer, etc.) embed equations as images rather than text. var cannot read images โ no variable detection or definition is possible for those equations. If you see very few highlights, this is likely why. arXiv preprints almost always use LaTeX-rendered text equations and work much better. When in doubt, use the arXiv version.
Variable Definitions
After rendering, var sends the first 8 pages of text to DeepSeek AI, which reads the paper's setup section and returns a plain-English definition for each detected symbol. For variables first appearing after page 8, a second targeted pass finds their first occurrence anywhere in the paper and runs a separate AI query. Hover any highlighted variable to see its definition. Click the pencil icon to write your own notes โ saved locally per paper.
Citation Detection
Citations are detected two ways: (1) from PDF annotation links embedded by the publisher, and (2) by regex scanning for author-year patterns like Smith (2020) or (Jones et al., 2021). Both handle Unicode names, hyphens, and multi-citation groups like (A, 2020; B et al., 2021). Blue underlines mark detected citations.
Citation Analysis
Hover any blue citation to get a one-sentence AI summary: what the cited paper found and why it's cited in that specific passage. var fetches the abstract from Semantic Scholar or CrossRef, then sends that plus ยฑ1 page of surrounding context to DeepSeek. Results are cached โ re-hovering the same citation is instant.
Past Papers
Sign in with Google to save papers. Each uploaded PDF is stored in Supabase (cloud storage) so you can reopen any past paper with one click. Swipe left on a card to reveal the delete button.