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TNToolsNexus

JSON formatter & validator

Format, validate, and minify JSON as you paste — 2/4-space or tab indentation, clear syntax errors, copy or download. Private.

Format as

Your JSON never leaves your browser — formatting happens on your device.

Paste JSON and get it back formatted, validated, or minified — live, with your choice of indentation, one-click copy, and a .json download. Invalid input gets the parser’s actual error message, not a shrug.

How to format JSON

  1. Paste into the box — formatting happens as you type, no button.
  2. Pick the style: 2 spaces, 4 spaces, tabs, or Minify.
  3. Copy the result or download it as a file.

The two jobs this does

Making JSON readable: an API response arrives as one 40,000-character line; pretty-printed at your indentation it becomes a structure you can actually scan, diff, and reason about. Making JSON small: the reverse trip strips every byte of optional whitespace before a payload ships. Both directions go through a real parse, which is what makes this a validator too — malformed input fails loudly with the engine’s own message instead of producing half-formatted garbage.

Honest notes on JSON itself

Everything here uses the standard JSON.parse/JSON.stringify, which means standard JSON semantics: duplicate keys keep the last value, numbers beyond 2⁵³ lose precision (IDs that long belong in strings), and comments aren’t JSON — if your “JSON” has comments, it’s JSONC and needs them stripped first. These aren’t limitations of this tool so much as facts about the format that bite people at 2am; better to read them here first. Encoded payloads inside your JSON? The Base64 decoder and URL decoder sit one click away.

Private by design

Real-world JSON is full of tokens, keys, and customer data — pasting it into a random website’s server is how leaks start. Here the parse and re-print run entirely in your browser; nothing is transmitted, logged, or retained.

Last updated:

Frequently asked questions

Is this also a JSON validator?
Yes — formatting requires parsing, so invalid JSON is caught immediately with the parser's error message (and the line and column, where your browser's engine provides them). If it formats, it's valid.
Does formatting change my data?
Only whitespace and key/value ordering exactly as written are preserved — values, strings, and numbers pass through the standard parser untouched. One classic caveat of every JSON tool: numbers beyond 2^53 lose precision, because that's how JSON.parse works everywhere.
When should I minify instead?
Minified JSON strips every optional space and newline — for config payloads, API bodies, and anywhere bytes count. Pretty-printed is for humans: diffs, code review, debugging.
Why tabs vs spaces as an option?
Because your repo already has an opinion. Two spaces is the JS-ecosystem default, four reads easier for deeply nested data, tabs match tab-indented codebases and let every reader choose their width.
Is my JSON uploaded anywhere?
No — and for API responses and config files that routinely contain keys and secrets, that matters. Parsing and formatting run entirely in your browser.

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