CleanJSON – Private JSON Viewer

Format, validate and explore JSON — fast, open-source, zero network requests, minimal permissions.

The JSON viewer that doesn't need your trust — because you can verify it. CleanJSON is 100% client-side: zero network requests, open-source, and permissions so minimal you can read every one of them in thirty seconds. Built for developers, API/QA engineers and data analysts who open JSON endpoints all day and are tired of choosing between a bloated formatter and an abandoned Manifest V2 extension. WHAT YOU GET • One click or one shortcut (Alt+Shift+J) — no auto-scanning of every page you visit. Click the toolbar icon or press the shortcut on a tab that looks like JSON, and CleanJSON takes over. • Collapsible tree with syntax highlighting, indentation guides and item counts — not a wall of colored text. • Search that keeps context — filtering to a match still shows its parent chain, so you never lose track of where you are in a large document. • Copy value, copy path, or copy the whole thing (pretty or minified) in one click. • Clickable URLs, right inside string values. • Real validation — when a response is broken you get the exact line and column, not Chrome's raw, unhelpful dump. • Correct with large integers. Most JSON viewers silently round IDs bigger than Number.MAX_SAFE_INTEGER (the classic Snowflake-ID bug). CleanJSON has its own parser built specifically to avoid that — what you see is the exact source text, always. • Fast on large files. The tree is virtualized: a 13MB response with 1.5 million JSON nodes renders in seconds and keeps the tab fully responsive, because only the visible rows ever touch the DOM. • Dark and light, following your system theme automatically — no toggle to hunt for. THE TRUST MANIFESTO IS A FEATURE, NOT A TAGLINE • Zero network requests, ever — open DevTools, go to the Network tab while using it, and see for yourself. • Open-source, public repository — read the code instead of taking our word for it. • Minimal permissions: activeTab, scripting, clipboardWrite, offscreen. No host permissions, no all_urls, no broad "read and change all your data" warning at install. • No ads, no install incentives, no third-party trackers, no account, no upsell. WHY A CLICK INSTEAD OF AUTOMATIC FORMATTING EVERYWHERE? True automatic formatting on every page you visit would require requesting broad host permissions — the exact "read and change all your data on every site" warning that makes people (rightly) suspicious of JSON viewer extensions. We chose not to ask for that. One click is a small price for a permission list you can actually read and trust. SINGLE PURPOSE Format, validate and explore JSON in the browser — collapsible tree, search, copy value/path, beautify/minify. Nothing else: no scraping, no batch export, no data collection.