What is kgdiff?
kgdiff is git diff for knowledge graphs. Give it two versions of a graph (an ontology release, a GraphRAG extraction, a lineage DAG) and it tells you what happened in the terms a reviewer thinks in: a term merged into another, a class moved under a new parent, a relation pointed somewhere else, a label renamed. You get the answer in the terminal, as a pull request comment, or in an interactive viewer that shows both versions on one stable map.
npx @kgdiff/cli before.obo after.obokgdiff mhd 2026-09-01 → 2026-10-01 179 → 184 nodes · 351 → 353 edges
+3 added ~12 modified ⇄7 restructured 58 changes in 22 hunks
+++++~~~~~~~~~~~~⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄⇄
Restructured 7
⊕ Merged “juvenile diabetes” and “insulin-dependent d… identity · via replacement h…
⊕ Merged “heart attack” into “myocardial infarction” identity · via replacement h…
⇄ Moved “Crohn disease” under “inflammatory bowel dis… structure · from “intestinal…
⑂ Split “diabetes insipidus” into “arginine vasopress… identity · inferred · 80% co…
…
Modified 12
~ Renamed “alcoholic liver disease” → “alcohol-relate… content · ~1 attribute · +1…
…Why not a text diff?
A text diff compares files. Rename one class in Turtle and every line that mentions it changes; merge two terms and you see a deletion plus edits scattered across the file; serialize the same graph again and everything looks different. kgdiff compares the graphs:
- It matches nodes across versions: by id, by replacement hints such as OBO
replaced_by, or by label and neighbourhood when ids mean nothing, as in two LLM extraction runs. - It classifies what changed: renames, id changes, types, synonyms, attributes, deprecation, moves in a hierarchy, merges, splits, retargeted relations and predicate changes.
- It groups changes into hunks, one per decision a reviewer makes, in an order that reads like a story: clean up (removed), restructure, refine (modified), grow (added).
- It ignores what does not matter: the same graph as Turtle or as N-Triples, or with its statements in another order, diffs as identical.
Ways to use it
| You want to… | Use |
|---|---|
| See what changed between two files | the CLI: Getting started |
| Explain every pull request that edits a graph | the GitHub Action, or the CLI in any CI |
| Explore a diff visually | an HTML report (-o report.html) or the playground |
| Show diffs in your own application | the <kgdiff-viewer> web component |
| Diff graphs in code | the libraries |
kgdiff reads RDF (Turtle, N-Triples, N-Quads, TriG, RDF/XML, JSON-LD), OBO and the common JSON graph formats (Formats). Everything runs locally: the CLI on your machine, the playground and the viewer in your browser. Nothing is uploaded.
Next steps
- Getting started: install the CLI and read your first diff.
- Playground: try the example datasets or your own files in the browser.
- Architecture: how kgdiff matches, classifies and draws changes.