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Primax Tools

JSON Formatter & Validator

Validate JSON, pretty-print it for reading or minify it for transport, with error messages that point to the exact line and column.

Runs entirely in your browser. Nothing is uploaded.

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Step by step

How to use the JSON Formatter & Validator

  1. 1

    Paste JSON into the input editor.

  2. 2

    Select Format to pretty-print, or Minify to remove whitespace.

  3. 3

    If the JSON is invalid, read the error with its line and column.

  4. 4

    Copy the output or download it as a .json file.

What it does well

Strict validation

Uses the standard JSON parser built into your browser, so results match what real applications accept.

Precise errors

Errors show line, column and a snippet of the surrounding text.

Indentation choice

Format with 2 spaces, 4 spaces or tabs.

Never executed

Input is parsed as data with JSON.parse, never evaluated as JavaScript.

Who uses it

API developers
Read and debug response payloads quickly.
DevOps engineers
Validate configuration files before deploying them.
Data analysts
Inspect exported records and confirm they are well formed.

Common JSON mistakes

JSON is stricter than JavaScript object syntax. Property names must be wrapped in double quotes, strings cannot use single quotes, trailing commas after the last item are not allowed, and comments are not part of the standard. Values like undefined, NaN and functions are invalid too. Most errors this validator finds fall into one of these categories.

Large numbers are another subtle trap: JSON allows arbitrarily long numbers, but JavaScript stores them as 64-bit floating-point values, so integers above 9,007,199,254,740,991 lose precision when formatted. If your data contains long IDs, store them as strings.

Pretty versus minified

Pretty-printed JSON is easy for people to read and review in version control. Minified JSON removes all optional whitespace, typically shrinking payloads by 10 to 30 percent, which matters for network transfer and storage. Both represent exactly the same data.

Frequently asked questions

Is my JSON sent to a server?

No. Parsing and formatting happen in your browser.

Can it fix invalid JSON automatically?

No. Automatic fixes can silently change data, so the tool shows you exactly where the problem is instead.

Does it support JSON with comments?

No. Comments are not valid in standard JSON and are reported as errors.

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