KOEN

JSON Formatter & Validator

JSON · FORMAT · VALIDATE

Beautify or minify JSON with 2-space, 4-space or tab indent, pinpoint errors by line and column, sort keys and browse a collapsible tree, all in your browser.

Waiting Paste JSON on the left to validate it instantly.
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Result

Your JSON is processed entirely in your browser and never sent anywhere. Numbers are output exactly as written, with every digit and notation preserved.

HOW TO

How to use

  1. Paste JSON into the input box, or press Open file or drag a .json file in.
  2. It's checked instantly: valid JSON appears formatted on the right, and errors show the exact line, column and reason. Use Jump to error in input to go straight there.
  3. Choose Beautify or Minify, 2 spaces, 4 spaces or tab indent, and optionally sort keys A–Z.
  4. Switch to the Tree tab to expand and collapse nodes, and click any item to copy its path (like $.menu[0].name).
  5. Press Copy result or Download to save a .json file.
PAIRS WELL WITH

Pairs well with

FAQ

FAQ

Is my JSON uploaded anywhere?

No. Parsing and formatting happen entirely in your browser, and nothing is sent to a server. Only your last input and options are remembered in this browser.

Can it tell me exactly where my JSON is broken?

Yes. It points to the line and column of the first problem and marks that line in red. Common mistakes like trailing commas, single quotes, unquoted keys, comments, missing commas or brackets and NaN or undefined come with a plain-English explanation and a fix.

Will formatting change big numbers or values like 1.50?

No. Numbers and strings are kept exactly as written, so large integers like 12345678901234567890, 1.50, 1e10 and escapes like \u00e9 come out unchanged, unlike tools that run everything through JSON.parse.

Can it handle large files?

Yes. The result view only draws the lines on screen, so even hundreds of thousands of lines scroll smoothly. Files over 3 MB skip the editor and are processed directly, and the tree shows items 200 at a time.