SafeJSON is a browser-local JSON toolkit for developers who inspect sensitive JSON, JWTs, schemas, logs, and API payloads with no pasted-content upload during core tool operations. You can verify this with DevTools.
Not just another JSON formatter. A verifiable local JSON toolkit for sensitive developer workflows.
Website:safejson.dev
You do not have to trust the claim.
- Open safejson.dev
- Open DevTools (F12) → Network tab
- Paste any JSON and run the formatter, diff, JWT decoder, JSONPath, or Schema
- Confirm: no request contains your pasted content
| Tool | What it does | Processing | Free / Pro |
|---|---|---|---|
| JSON Formatter | Instant syntax-highlighted formatting with collapsible tree view | Browser-local | Free |
| JSON Validator | Error detection with line and column numbers | Browser-local | Free |
| JSON Beautifier | Configurable indentation (2, 3, or 4 spaces) | Browser-local | Free |
| JSON Viewer | Collapsible tree view for navigating large objects | Browser-local | Free |
| JSON Parser | Inspect structure, types, and nesting depth | Browser-local | Free |
| CSV ↔ JSON | Convert between CSV and JSON formats | Browser-local | Free |
| JSON Diff | Side-by-side comparison with color-coded results | Browser-local | Pro |
| JWT Decoder | Decode header, payload, and signature | Browser-local | Pro |
| JSONPath Query | XPath-like queries against JSON data | Browser-local | Pro |
| JSON Schema Validator | Validate against draft-04 through 2020-12 (Ajv) | Browser-local | Pro |
| Browser Extension | Auto-detect and format raw JSON on any URL | Browser-local | Free |
All core processing is browser-local. No pasted-content upload. No pasted-content analytics.
Developers paste API responses, JWTs, credentials, config files, logs, and production payloads into online JSON tools every day — often without checking where that data goes.
In November 2025, popular JSON formatting sites were found to have leaked over 80,000 credentials through server-side processing. Attackers were actively harvesting the data within 48 hours of the discovery.
SafeJSON was built so core JSON workflows are browser-local and verifiable. You can check the pasted-content boundary yourself with DevTools.
| Asset | What it shows |
|---|---|
 | Formatter: no pasted-content upload |
 | Diff: comparison runs locally |
 | JWT: token decoded locally |
Core tools are free forever. Formatter, validator, beautifier, viewer, parser, and CSV conversion.
Pro is $5/month or $39/year. Unlocks JSON Diff, JWT Decoder, JSONPath Query, and JSON Schema Validator. Pro tools are built for sensitive JSON workflows — diff, decode, query, and validate with no pasted-content upload for core tool inputs. One license activates up to 2 devices. 5 free trials per tool.
Payment and license delivery handled by Lemon Squeezy.
Auto-detects and formats raw JSON responses on any URL.
- Edge Add-ons:Live on Microsoft Edge Add-ons
- Chrome Web Store: pending review
- Permissions explained:How the extension works
- No remote code, no ads, no affiliate injection. Source is auditable on GitHub.
Manual install from source:
git clone https://github.com/Json-Lee-git/SafeJSON
# Open chrome://extensions or edge://extensions# Enable Developer Mode → Load unpacked → select extension/ folderFormatter and Beautifier tested with 50MB JSON locally. Viewer and Parser support large local workflows. Large JSON is parsed with a Web Worker so the UI stays responsive in the tested formatter and beautifier workflows, with no pasted-content upload.
- Not "zero network requests" (SafeJSON uses GA for aggregate analytics)
- Not "no tracking" (GA is installed; pasted content is never sent to analytics)
- Not "guaranteed private" or "enterprise-grade security"
- Not "SafeJSON handles 50MB everywhere" (only Formatter + Beautifier tested)
- Not Team / Self-hosted / SSO / compliance yet
Next.js 16 · React 19 · Tailwind CSS · Phosphor Icons · Vercel (static prerendering) · Lemon Squeezy License API
npm install
npm run devChecks:
npm run lint
npm run build
npm run growth:check
npm run privacy:sentinel- Website:safejson.dev
- Verify local processing:How to verify
- Extension permissions:How the extension works
- Privacy policy:safejson.dev/privacy
- Product Hunt:SafeJSON on Product Hunt
- SaaSHub:SafeJSON on SaaSHub
- Indie Hackers:SafeJSON on Indie Hackers
- Edge Add-ons:SafeJSON on Edge Add-ons
- YouTube:How to Verify Any JSON Formatter Is Safe
- Security guide:How to check if an online JSON formatter uploads your data
- GitHub Discussions:Join the discussion
- GitHub Issues:Report a bug
MIT