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Developer Tools · Updated October 17, 2026

JSON Formatter & Validator

You can format, minify and validate JSON in your browser, with syntax errors reported by line and column so you can find the mistake in a large payload quickly.

Runs in your browserFree · No sign-up · No watermark
JSONRuns in your browser
Loading the tool…

Everything runs locally in this tab. No file is uploaded while the tool loads.

This tool runs in your tab. Nothing is uploaded and no copy is stored.

How files are handled

At a glance

Formats
JSON → JSON
Processing
In your browser
Max size
Up to 8 MB of pasted JSON
Price
Free, no account
Updated
October 17, 2026
All Developer Tools

About JSON Formatter

APIs and configuration files hand you JSON as one long line, which is fine for a machine and miserable for a human. This formatter parses the text and prints it with two-space or four-space indentation, optionally sorting object keys alphabetically, so nested objects become readable at a glance. Minify does the reverse when a payload needs to be as small as possible.

Validation is the other half. Most parsers only tell you that the JSON is broken; this one scans the text and points at the exact line and column, with the surrounding lines shown for context. Trailing commas, single quotes, comments and unquoted keys are called out by name, because those are the mistakes strict JSON does not allow.

What this tool does

The details that matter when you use JSON Formatter for real work.

  • Errors with line and column

    A failed parse shows the exact position plus a snippet of the offending line and a caret, so you are not guessing where the payload broke.

  • Format, minify or validate

    Pretty-print with your chosen indentation, collapse the payload to one line, or check validity without changing the output pane.

  • Optional key sorting

    Sort object keys alphabetically at every nesting level to make two JSON files easier to compare in a text diff.

  • Designed for large payloads

    Parsing runs after the UI has painted, and inputs over 8 MB are refused with a clear message instead of freezing the tab.

  • Copy in one click

    A dedicated copy button puts the formatted or minified result on the clipboard and confirms when the copy has happened.

  • Sample and clear

    Load an example payload to see how each mode behaves, then clear both panes and start again with your own data.

How to use JSON Formatter

No account, no installation — the whole job happens in this browser tab.
  1. 01

    Paste or load JSON

    Paste your JSON into the input pane, or press Sample data to try the formatter with a small example payload.

  2. 02

    Choose an action

    Press Format to pretty-print, Minify to strip optional whitespace, or Validate to check the syntax without replacing the output.

  3. 03

    Set indentation and sorting

    Pick two spaces, four spaces or a tab from the indent menu, and tick Sort object keys if alphabetical order helps you compare files.

  4. 04

    Fix the reported error

    If validation fails, read the line and column in the message and correct that spot in the input before running the action again.

  5. 05

    Copy the result

    Use Copy output to place the formatted or minified JSON on the clipboard, ready to paste into an editor, request body or test fixture.

Supported formats and limits

Input
JSON
Output
JSON
Processing
Client-side, in your browser. Nothing is uploaded.
Maximum size
Up to 8 MB of pasted JSON
Requirements
Chrome, Edge, Firefox or Safari · JavaScript enabled

Limitations worth knowing

  • Strict RFC 8259 only: JSON5 features such as comments, trailing commas and single quotes are rejected rather than repaired.
  • Input is capped at 8 MB; larger payloads are better handled by a command-line formatter or a code editor.
  • Formatting preserves the data but not your original whitespace or key order unless sorting is enabled; numbers are re-serialized by the browser's JSON implementation.

Privacy and file handling

Everything runs inside your browser tab. The JSON is parsed, formatted and validated locally with JavaScript, and no part of it is sent to FormatFlow or any third party. Nothing is stored after you close the page.

Read the full privacy policy

JSON Formatter FAQ

Short, direct answers to the questions people ask before using this tool.
What is the difference between formatting and validating JSON?
Formatting parses valid JSON and prints it with indentation. Validating only reports whether the text is valid and where the first error is. Minify parses the JSON and prints it again without optional whitespace between tokens.
Why does JSON reject comments and trailing commas?
The JSON specification, RFC 8259, allows only objects, arrays, strings, numbers, true, false and null. Comments and trailing commas are JavaScript conveniences that are not part of the grammar, which is why strict parsers reject them.
Can the formatter repair broken JSON automatically?
No. It reports the first syntax error with its line and column; it does not guess or rewrite invalid input. Common slips such as a trailing comma are quick to fix at the position shown, but missing brackets need your judgement.
How large a payload can I format?
Inputs up to 8 MB are accepted. Parsing happens locally, so a desktop browser handles a payload of that size in well under a second; mobile browsers may be slower because they have less memory available to the tab.
Does sorting keys change the meaning of my JSON?
No. JSON objects are unordered collections by definition, so alphabetical key order represents the same data. Arrays are left in their original order and are never sorted by the option.
Is my JSON uploaded to a server?
No. The formatter parses, sorts and prints the text inside this browser tab, and no copy is sent to FormatFlow or any third party. Avoid pasting live secrets such as private keys anyway, since browser extensions can read page content.
Why does my JSON work elsewhere but fail here?
Some editors and languages accept extensions such as comments, unquoted keys or single-quoted strings. This tool enforces strict RFC 8259 JSON, so text written for JSON5 or JavaScript object literals needs to be converted before it will validate.
Can I compare two JSON files with this tool?
There is no side-by-side compare mode. Formatting both files with sorting enabled makes a text diff more useful, but you still need a diff tool to see exactly what changed between the two payloads.

Background reading

Format guides that explain the trade-offs behind JSON Formatter.