PDFCure
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Format and Validate JSON Online, Free

Format, validate and minify JSON — pretty-print it or collapse it to one line.

Most tools run entirely on your device

Parsed and formatted in your browser — nothing is uploaded.

About formatting JSON

Minified or badly-indented JSON — a single dense line from an API response, or a config file someone saved without formatting — is nearly unreadable until it's properly indented. This tool formats, validates and beautifies JSON, and flags exactly where a syntax error is if the input isn't valid.

It parses the JSON directly in your browser's JavaScript engine, re-serializes it with consistent indentation, and reports a clear error with the problem location if parsing fails — rather than a cryptic stack trace. Nothing is sent anywhere; formatting happens the instant you paste.

Supported files

No file — paste JSON text. Produces the same data, reformatted and validated, or a clear error if it's invalid.

Is my file uploaded?

Yes, completely private. JSON is parsed and formatted entirely in your browser — never sent anywhere.

How to JSON Formatter

  1. 1

    Paste your JSON

    Drop in the JSON you want to check or tidy.

  2. 2

    Format or minify

    Format pretty-prints it with your chosen indent; Minify collapses it to one line. Invalid JSON shows the error.

  3. 3

    Copy the result

    Copy the formatted output to your clipboard.

JSON Formatter — frequently asked questions

Is my JSON sent to a server?+

No. It's parsed and formatted entirely in your browser with JSON.parse.

It says invalid JSON — why?+

The message shows where parsing failed. Common causes: trailing commas, single quotes, or unquoted keys — none of which are valid JSON.

Can it handle large files?+

Yes, within your browser's memory. Very large files may be slow to render.

Is there a free JSON formatter and validator online?+

Yes — this tool formats and validates the JSON entirely in your browser, free and with nothing uploaded.

Do you upload my files to a server?+

No — every tool here processes your files entirely on your device, and nothing is uploaded to a server. The only exception is the AI tools, which send the extracted text (not the file) to Claude to do their work.

Is there a file size limit?+

There's no artificial limit we impose, but since processing happens in your browser, very large files (500+ MB or 1,000+ pages) are limited by your device's memory rather than by us.