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Prepare, check, then export

JSON Formatter & Validator

Make a JSON payload readable without changing its numbers. Validate the structure, choose indentation, and download the result or format several files together.

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Benefits

  • Preserve original number tokens, including large IDs and decimal notation.
  • Stop on duplicate keys before an object silently loses a value.
  • Use two spaces, four spaces, tabs or compact output; optionally sort object keys.

When this helps

  • Check an API response before adding it to a bug report.
  • Format configuration files consistently for review.
  • Prepare exported records for CSV conversion or a readable PDF.

How to use this tool

  1. Paste JSON or import a UTF-8 JSON file.
  2. Choose formatting and optional key sorting.
  3. Select Validate and format. Correct any line and column error in the source.
  4. Copy, download JSON, continue to another tool or choose several files for a ZIP.

A formatter should not change an identifier

An order ID can look like a number while behaving like a label. The value 9007199254740993 is valid JSON, but converting it through a JavaScript Number can round it. This formatter keeps each numeric token as written. Decimal places, exponent spelling and a negative zero survive formatting because the tool changes layout rather than evaluating those values.

Duplicate keys deserve a separate check. Two entries called status in one object can tell different systems different stories. Some parsers keep the last value, while other software rejects the document. MAXScanner stops and asks you to choose the intended entry. Escaped keys are compared by their decoded text, so two spellings of the same name are still treated as duplicates.

Pretty printing and minifying serve different jobs. Indentation makes a nested response easier to review; compact output removes whitespace outside strings. Neither mode shortens the content inside a string. Sorting changes the order of object entries but leaves arrays in their original order. Keep sorting off if a reviewer expects to see the source sequence.

The validator accepts standard JSON rather than JavaScript object literals. Comments, trailing commas and single-quoted strings need correction in the source. It also rejects unpaired Unicode surrogates so a later UTF-8 download will not replace them silently. Validation checks structure, not whether a price, date or account number is correct. Compare important fields with the originating system before sending the result onward.

Formats, limits and privacy

  • Up to 100,000 UTF-16 code units per input; UTF-8 TXT, JSON, CSV or TSV files up to 1 MiB.
  • Batch ZIP: up to 10 files, 5 MiB combined. Successful outputs and a numbered error report are kept together.
  • Document handoffs support results up to 100,000 code units without NULL characters. Larger results remain downloadable.
  • Up to 64 nesting levels and 20,000 values. Duplicate keys, unpaired Unicode surrogates, a leading BOM and JSONC comments are rejected. This is syntax validation, not JSON Schema validation.

These tools process text locally. There is no draft autosave. Download important work before leaving; temporary file handoffs expire after 30 minutes.

Frequently asked questions

Does formatting round large JSON numbers?

No. Number tokens are preserved without converting them to JavaScript Number values.

Can I format several files?

Yes. Batch conversion uses the selected indentation and sorting settings, with a separate output or error for each file.

Does this repair invalid JSON automatically?

No. It reports the first problem with a line and column. You decide how the source should change.

Continue your document workflow

Use a Continue button inside the workspace to carry your text; these links open a fresh tool.