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Lemma for Mac

An IDE for reading math: a free PDF reader that understands textbooks and papers like editors do.

By fus3r. Free and open source, GPL-3.0 licence.

Get it with OpenDMG View source on GitHub

Lemma at a glance

Version
3.6.0
Released
6 November 2026
Download size
34 MB
Works on
Apple silicon and Intel
Licence
GPL-3.0
Category
Utilities
Developer
fus3r
GitHub stars
15

About Lemma

An IDE for reading mathematics: a free, open-source PDF reader for the Mac that turns references into links, proofs into steps and checks derivations as you write them.

Screenshots

Lemma screenshot 1Lemma screenshot 2Lemma screenshot 3

How to install Lemma on a Mac

  1. Get OpenDMG. It is a free app store for open source Mac apps. Download OpenDMG.
  2. Search for Lemma and press Get. OpenDMG downloads version 3.6.0 from fus3r's own GitHub release.
  3. Open it. The download is checked against its SHA-256 fingerprint and its signature is checked on your Mac before it lands in Applications.

Updates to Lemma show up in OpenDMG and install with one button. No account is needed.

Prefer to do it by hand? The developer's file is on GitHub: Lemma.dmg (34 MB).

What is new in Lemma 3.6.0

PDF annotations, workspace editing, and shared-window reliability.

- Annotate PDFs with the shared toolbox: pen, boxes, ellipses, lines, arrows and eraser; custom colors, widths, dashed outlines and translucent fills; move and resize shapes, Undo/Redo, and export a separate annotated PDF. Saved notes open in Preview, with Edit explicit.
- Highlight geometry follows individual text lines, including mathematical scripts, adjacent lines, columns and rotated pages. Drawing, hit testing, resizing and PDF export use the same bounds.
- A compact, named highlight palette with configurable shortcuts for each color and separate highlight/underline defaults. Existing marks retain their saved colors.
- A native workspace text editor with line numbers, Markdown syntax colors, word wrap, Find/Replace, and math preview beside the file. Shared file buffers stay synchronized, and failed saves keep unsaved work open when closing a file, window or the app.
- Search results, statement references, symbol definitions, breakpoints, the first “?” and active proof-debugger actions reveal their PDF when a text file or another editor is in front. Files retain their tabs and text; session restoration preserves the chosen foreground editor.
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