JSON Formatter and Validator
Paste JSON to format it, find errors with the exact line and column, and fix common mistakes in one click. Everything runs in your browser, so your data never leaves your device.
Free · No sign-up
How to use it
- Paste your JSON into the input box, open a .json file, or load the sample.
- Read the result. Valid JSON is formatted instantly. If there is an error, the message shows the line, the column and what to change.
- If the error is a common one, such as a trailing comma, single quotes or comments, press Repair JSON to fix it automatically.
- Choose 2 spaces, 4 spaces, tabs or Minify, switch to Tree view to explore nested data, then copy or download the result.
Why use this tool
Errors you can act on
Instead of a vague parser message, you get the line, the column, a pointer to the exact spot and a plain explanation of the fix.
One-click repair
Fixes trailing commas, single or curly quotes, unquoted keys, comments, missing commas and Python True, False and None.
Tree view with paths
Fold and unfold nested objects and tap any value to copy its path, such as $.data[0].id.
Exact numbers
Large IDs and long decimals keep every digit. Many formatters built on JSON.parse silently round them.
Private by design
Your JSON is processed in your browser. There is no upload, no saving and no shareable link that could expose it.
Works on your phone
The editor, buttons and tree are built for touch screens as well as large monitors.
What does a JSON formatter do?
JSON (JavaScript Object Notation) is the text format most web APIs, configuration files and apps use to exchange data. Machines often send it as one long line with no spaces, which is hard for people to read.
A formatter, also called a beautifier or pretty printer, adds line breaks and indentation so you can see the structure. A validator checks that the text follows the JSON rules. This tool does both at once, and the minify option does the reverse: it removes all optional whitespace to make the file as small as possible.
Common JSON errors and how to fix them
Most invalid JSON comes from a handful of mistakes, often because the text was copied from JavaScript, Python or a configuration file. All of these can be fixed with Repair JSON.
| Error | Invalid example | Valid JSON |
|---|---|---|
| Trailing comma | [1, 2, 3,] | [1, 2, 3] |
| Single quotes | {'name': 'Ana'} | {"name": "Ana"} |
| Key without quotes | {name: "Ana"} | {"name": "Ana"} |
| Comment | {"a": 1 // note} | {"a": 1} |
| Python values | {"ok": True, "x": None} | {"ok": true, "x": null} |
| Missing comma between lines | {"a": 1 ⏎ "b": 2} | {"a": 1, "b": 2} |
Is it safe to paste JSON into an online formatter?
JSON often contains API keys, tokens, email addresses or customer data. In November 2025, security researchers reported that popular online code formatters had exposed thousands of saved snippets, including passwords and API keys, through a public list of recently saved links.
This formatter has no save or share feature and no server-side processing. The page loads once and then works entirely in your browser, so the JSON you paste is never sent anywhere. Even so, it is good practice to remove real secrets before pasting data into any website.
Formatting options explained
- 2 spaces: the most common style, used by JavaScript projects and most API documentation.
- 4 spaces: easier to scan for deeply nested data, and common in Python projects.
- Tabs: one tab per level, so each person's editor decides the visual width.
- Minify: removes every optional space and line break. Use it for smaller files and request bodies.
- Sort keys A to Z: puts object keys in alphabetical order, which makes two JSON files easier to compare.
- Tree view: shows objects and arrays as foldable branches with item counts. Tap a value to get its path.
Why large numbers stay exact here
JavaScript stores numbers as 64-bit floating point values, so any integer above 9,007,199,254,740,991 loses precision. A 19-digit database ID can change its last digits if a tool formats it with JSON.parse and JSON.stringify.
This formatter reads numbers as text and writes back exactly the digits you pasted. When it finds such numbers, it tells you, so you know your own code may need to treat them as strings or BigInt.
Frequently asked questions
Is this JSON formatter free?
Yes. It is free with no sign-up, no limit on the number of uses and no watermark or ads inside the tool.
Is my JSON uploaded or stored?
No. Formatting, validation and repair all run in your browser. Nothing you paste is sent to a server or saved, and there is no share link.
Does formatting change my data?
No. Formatting only changes spaces and line breaks. Strings, numbers and key order stay the same unless you turn on Sort keys. Repair changes syntax only, for example quotes and commas, and lists every fix it made.
What can Repair JSON not fix?
It does not guess missing values or brackets that make the structure ambiguous, for example {"a": } or an object that is cut off in the middle. In those cases the error message shows where the problem is so you can fix it by hand.
How large a file can it handle?
Files of several megabytes work on a typical computer. Up to 500 KB the result updates as you type. For larger input, press Format JSON. Very large files are shown without colors to stay fast.
Does it support JSON5 or comments?
Standard JSON does not allow comments, so the validator reports them as errors. Repair JSON removes comments and also accepts other JSON5-style syntax such as single quotes, unquoted keys and trailing commas, and turns it into standard JSON.
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