JSON Semantic Diff is a local-first JSON comparison app focused on meaningful differences rather than line-oriented text changes. It matches reordered array rows by inferred identity, normalizes noisy fields like timestamps, and shows you what actually changed — not just where the bytes moved.
Click Load example in the demo. The inventory array is deliberately reordered and partially edited between inputs. Most JSON diff tools would report every reordered row as fully added/removed. JSON Semantic Diff instead infers an identity key (e.g. store + sku), matches rows across inputs by that identity, and surfaces only the fields that actually changed — with a confidence score and reasoning breakdown for every match, and a manual override if you disagree with its inference.
npm install
npm run start --workspace=packages/uiOpen http://localhost:4200.
Production build:
npm run build --workspace=packages/ui- Tree and raw-source diff views, side by side
- Smart array row matching by inferred identity (not just position)
- Confidence-scored matching analysis with manual override
- Timestamp and numeric-string normalization
- Ignore-path rules with wildcards
- Entire comparison runs in the browser — nothing is uploaded
Just want the diffing logic, not the UI? The core engine is framework-free and published to npm:
npm install json-semantic-diffimport { diffJson } from 'json-semantic-diff';
const result = diffJson(original, changed);The package is ESM-only (no CommonJS require support) and requires Node ≥22.
See packages/core/README.md for the full API reference.
This repo is an npm-workspaces monorepo:
packages/core— the framework-free diff engine, published to npm asjson-semantic-diffpackages/ui— the Angular app that consumes it
- Angular 22
- Node 24
- TypeScript 6
- Angular CDK
- Tailwind CSS 4 + CSS variables
Node version is pinned via .nvmrc (currently v24.17.0) — run nvm use from the repo root before installing/building.
Identity inference lives in packages/core/src/diff/matching/identity-inference.ts. Candidate quality considers uniqueness, completeness, match coverage, overlap, type consistency, a weak field-name hint, and volatility penalties. JSON Semantic Diff only auto-applies a candidate when both its score and its lead over competing candidates are strong enough.
The hosted demo uses GoatCounter for anonymous, cookie-free page-view analytics. It sets no cookies, no persistent identifiers, and collects no personal data — see GoatCounter's privacy policy. Local development traffic (localhost and private IP ranges) is never tracked.
See CONTRIBUTING.md for setup, dev commands, and PR process, and AGENTS.md for product and implementation constraints. Licensed under MIT.