JSON Toolkit

Format, validate, and compare JSON — 100% offline, no data leaves your browser.

JSON Toolkit — Format, Compare, Decode & Convert. 100% Offline. The all-in-one JSON utility that lives right in your browser toolbar. No servers, no accounts, no telemetry — everything runs locally on your machine. ━━ FEATURES ━━ 🔧 FORMAT & VALIDATE • Instantly pretty-print or minify any JSON • Real-time syntax validation with clear error messages • Auto-repair common JSON mistakes: trailing commas, single quotes, unquoted keys, JS-style comments • Sort keys alphabetically for consistent diffs • Choose your indentation: 2 spaces, 4 spaces, or tabs • Syntax highlighting for easy reading • Input history — revisit your recent snippets 🔍 COMPARE • Side-by-side JSON diff viewer • Highlights added, removed, and changed values • Perfect for API response debugging and config audits 🔑 JWT DECODER • Paste any JWT and instantly decode the header and payload • Verifies structure and displays expiry, issuer, and all claims • Works with any JWT — no secret needed to decode 🔄 CONVERT • JSON ↔ YAML • JSON ↔ CSV • Instant conversion with formatted output 🌙 DARK MODE • Comfortable light and dark themes, saved across sessions ━━ PRIVACY FIRST ━━ JSON Toolkit is 100% offline. Your data never leaves your browser — no network requests, no analytics, no external scripts. It works even without an internet connection. No permissions required. No host access. No cookies. ━━ PERFECT FOR ━━ • Backend & frontend developers debugging API responses • DevOps engineers inspecting configuration files • QA engineers comparing test payloads • Anyone who works with JSON daily ━━ OPEN SOURCE ━━ Clean, auditable code. Zero external dependencies.