Big JSON Viewer

A virtualized, browser-based viewer for large JSON files — tested with 500 MB files, and the ceiling is your browser’s memory, not the app. Search, fold, and copy stay fast, and your data never leaves your machine.

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Features

Built for large JSON filesA canvas-backed virtualized tree renders only the visible rows, so once a file is parsed, scrolling, folding, and searching stay fast regardless of depth or file size.
Local-onlyEverything runs in your browser. Your JSON is never uploaded, logged, or sent to any server.
Practical toolingTabbed workspace, key-path copy, formatted-vs-raw view, regex-friendly search, dark mode, and nine languages.

FAQ

Common questions about Big JSON Viewer.

How large a JSON file can I open?

The app itself has no size limit — the ceiling is your browser’s JSON parsing and memory budget. 500 MB files are tested and work in Chrome, and larger ones load too if your machine has the memory. Once parsed, our virtualized tree renders in constant time regardless of file size, so the size you can comfortably read is set by your browser, not by us.

Is my data uploaded anywhere?

No. The viewer runs entirely in your browser. Your file is never sent to a server.

Can I open multiple files at once?

Yes — drag multiple JSON files in or use the tabbed workspace to split and move panels like a code editor.

From the blog

Embed a JSON Snippet in Your Page with an iframeRender any JSON snippet as a collapsible tree inside an iframe on your own site. The data rides in the URL hash — gzipped and base64url-encoded — so nothing is uploaded. Here is the exact payload spec.
Why JSON Viewers Stall on Rendering, Not ParsingMost JSON viewers freeze at 50 MB because they render millions of DOM nodes. Parse capacity is a browser-imposed ceiling we can’t fix, but the rendering bottleneck is fixable — and that’s where Big JSON Viewer wins.
Local-Only by Design: Why a JSON Viewer Should Never See Your DataThe privacy story behind Big JSON Viewer is also the architecture: no server, no upload, no logs, no telemetry on your file contents. Here is what that looks like in practice.
Big JSON Viewer vs jq, JSON Crack, and Chrome DevToolsA practical comparison of four very different JSON tools, with use cases where each one is actually the right choice — and the cases where each one breaks down.
Sharing 500 MB of JSON in the Browser: Resumable Uploads and Gzip StreamingHow we share 500 MB JSON files via the user’s own Google Drive, with chunked resumable uploads, client-side gzip, abortable progress, and transparent decompression on the recipient side.
Migrating from Vite to Next.js for SEO: What Actually Moved the NeedleWe moved Big JSON Viewer from a Vite SPA to Next.js to fix indexability. Here is what helped, what we expected to help but didn’t, and what was the framework just doing the work for us.