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Large JSON File Viewer

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To open a large JSON file, drop it onto this page: files over 5 MB are parsed in a background worker and shown with virtual scrolling, so a 100 MB export stays browsable without freezing the tab. Nothing is uploaded, so there is no transfer wait or server size limit.

The file is read from your disk by your browser and is never uploaded. How we protect your data

100% in-browserOnline
Large file mode: drop files up to 300 MB. Above 5 MB the work runs in a background worker, syntax highlighting is switched off and the tree is virtualized so the page stays responsive. Auto-format pauses; press Format when you are ready.

Input

Loading editor…

Paste JSON here

or drop a .json file anywhere in this box. Everything stays in your browser.

Output

Paste JSON to see it as a table.
Loading editor…
Paste JSON, drop a file, or try the sample.

How to use the large json viewer

  1. Close other heavy tabs if the file is several hundred megabytes.
  2. Drop the .json file onto the input or use Upload; avoid pasting, which is slower for huge text.
  3. Parsing runs in a background worker, so the page stays responsive; loading a different file replaces the current one.
  4. Browse the virtualized tree, search for keys, or switch to code view with Ctrl/Cmd+Alt+T.
  5. Copy a single subtree or path instead of the whole document.

Features

  • Web Worker parsing: Large-file mode starts above 5 MB so scrolling and typing stay responsive.
  • Virtual scrolling: Only visible lines and nodes are drawn, however long the document is.
  • Background parsing: Large files are parsed in a Web Worker and previewed in a virtualized read-only view, so the tab doesn't freeze.
  • Local file reading: No upload limit or transfer time; your device's memory is the limit.

Example

Database export (one array of records) → browsable tree

Input

[
  {"id":1,"email":"a@example.com", ... 12 fields},
  {"id":2, ...},
  ... 400,000 records
]

Output

▾ root [400000]
  ▸ 0 {12}
  ▸ 1 {12}
  ...
  ▸ 399999 {12}

Illustrative. Actual load time depends on file size, structure, device and browser.

How much memory does a big JSON file need?

A parsed document takes several times its file size in memory, because every string, number and object becomes a JavaScript value. Files of 100 MB and more open on typical desktop browsers; phones and tablets have far less memory per tab and manage much smaller files.

If the tab runs out of memory the browser stops it with an error page. Reload, close other tabs and try again, or extract the part you need on the command line first, for example with jq '.records[:1000]' big.json.

Working efficiently with huge documents

Avoid Expand all on a document with hundreds of thousands of nodes; expand to level 1 or 2 and drill down. Use search to jump to a specific ID rather than scrolling. When you need a slice for a bug report or test, copy that subtree only, and run it through the secret scanner first if it is production data.

Large JSON Viewer FAQ

How do I open a large JSON file?

Drop it onto this page. Big files are parsed in a background worker and shown with virtual scrolling, so you can browse them without the tab freezing.

What is the maximum JSON file size?

There is no fixed limit because nothing is uploaded. The practical limit is your browser's memory: 100 MB+ works on typical desktops, much less on phones.

Why do other JSON viewers crash on big files?

Many parse and render everything on the main thread, creating millions of page elements at once. That blocks the browser until it gives up.

Why is a file that opens in a text editor slow to view as JSON?

A text editor only shows characters. A JSON viewer must parse every value and build a tree, which needs more CPU and memory.

Can I open JSON Lines (NDJSON) logs?

Not yet; NDJSON support is planned. For now, a file that is one JSON array or object works.

Can I edit a 100 MB JSON file here?

Large-file mode is built for viewing, searching and copying. For bulk edits, a script or jq is more reliable than editing that much text in a browser.

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