JSON Formatter & Viewer

JSON formatter, validator, viewer & diff with a live WebSocket inspector. Tree view, search, files up to 10 MB. No ads or tracking.

JSON Formatter & Viewer — a fast, lightweight tool for developers to format, validate, explore, transform and compare JSON data. Handles JSON files up to ~10 MB. — Format & beautify — ✅ Format & beautify JSON with proper indentation ✅ Minify JSON to a single line ✅ Sort object keys alphabetically (recursive) ✅ Validate syntax in real-time with clear error messages ✅ Auto-format on paste or file drop — Explore — ✅ Interactive tree viewer with expand / collapse ✅ Expand to any depth level (1–10) with one click ✅ Search with live highlight, match count, and case-sensitive mode ✅ Copy any value or path from the tree — Undo & history — ✅ Undo the last Format, Sort Keys or Auto-format in one click ✅ Browse recent states and jump back to any of them (up to 30 entries, 5 MB total) ✅ History is remembered between sessions — Compare — ✅ Side-by-side JSON diff view ✅ Tree-based comparison with added / removed / changed filters ✅ Toggle unchanged keys to focus on differences — Import & export — ✅ Paste from clipboard or drag & drop files (up to ~10 MB) ✅ Load JSON from a URL ✅ Read live JSON straight from a page's WebSocket (see below) ✅ Download as .json file ✅ Load a sample JSON to try it instantly — Live WebSocket JSON — Debugging an app that talks over a WebSocket? Instead of copying payloads out of DevTools by hand, the WebSocket tab gives you every message in the same tree viewer you already use — messages on the left, formatted JSON on the right. ✅ Incoming and outgoing messages, newest first, with timestamp and size ✅ Click a message to explore it in the tree viewer, at any depth ✅ Binary frames are decoded and marked ✅ Filter by direction or by socket when a page opens more than one ✅ Fold repeated keepalive frames into a single row with a count ✅ See connection open, close and error events, so a dropped socket is visible ✅ Compare any two frames side by side in the diff view ✅ Copy a frame, or send it to the editor for the full toolset ✅ Export the frames you see as a JSON file ✅ Works on your own localhost dev server too How to use it: open the page you are debugging → click the extension icon → WebSocket tab → "Allow on this site" → reload the page. Capture has to start together with the page, so the reload is required. — Side panel — Pin the formatter to Chrome's side panel and it stays open while you browse — no more reopening the popup after every click. ✅ One click on Pin docks the app to the right side of the browser ✅ Keeps working while you interact with the page — perfect for watching live WebSocket traffic ✅ While pinned, the extension icon opens the side panel — even after a browser restart ✅ Unpin any time to return to the compact popup — Share — ✅ One-click share link (data lives in the URL, never hits any server) — UX — ✅ Dark & light theme with preference remembered ✅ Editor and viewer state persisted between sessions ✅ No ads, no tracking, no data collection — everything runs in your browser — Permissions & privacy — The extension asks for access to a website only when you press "Allow on this site" on the WebSocket tab, and only for that one site. Nothing is requested at install time, and no site is watched until you approve it. WebSocket messages are read only — nothing on the page is modified, blocked or injected. Captured messages stay in the memory of that tab, capped at 500 messages, and are gone when you close or reload it. They are never uploaded anywhere: the extension has no backend and no analytics. You can revoke a site at any time in chrome://extensions → JSON Formatter & Viewer → Site access. Full privacy policy: https://json.fedrr.com/privacy.html Simply click the extension icon, paste your JSON, and format it instantly. Also available as a web app at https://json.fedrr.com