Dev Tools

JSON Formatter & Validator

Validate and format JSON for readability, with exact error locations — free, no sign-up required

✓ 100% free✓ No sign-up✓ Runs in your browser✓ No data stored

JSON (JavaScript Object Notation) is the most widely used format for sending data between a website and an API, because it's easy to read and maps directly onto data structures. But JSON coming from an API or a log file is often squeezed onto a single long line that's hard to read, and a single misplaced comma or bracket can break the whole file. This JSON Formatter & Validator checks whether the JSON you paste is syntactically correct — if it isn't, it tells you the exact line and column where the problem is. If it is valid, you can format it with readable indentation, or minify it to a single line for production use. Everything runs entirely in your browser — no data is ever sent to a server.

How to use the JSON Formatter

1

Paste your JSON

Copy the JSON you want to check into the text box

2

Format or minify

Click Format for readable indentation, or Minify for a single line

3

Fix using the reported location

If the JSON is invalid, the exact line/column is reported immediately

Why use this tool

✓

Find errors fast

Reports the exact line and column of a syntax error

✓

Format and minify in one place

No need to switch between two tools

✓

Private by design

JSON is never sent to a server, even sensitive data

Example use cases

Checking an API response before using it

When your frontend code can't read a value from an API response, paste the response here first to check whether the format is correct and where it breaks.

Formatting minified JSON to make it readable

Some config or log files are squeezed onto a single line — format them with indentation to make the structure easier to follow.

Minifying JSON before shipping it

Before deploying or embedding JSON in a real request, minify it to a single line to reduce file size.

Finding a typo in a long JSON file

A config file with hundreds of lines can hide a single typo that's impossible to spot by eye — this tool points you straight to the line and column.

Checking a config file before committing

Verify that a hand-edited file like package.json or tsconfig.json is still valid JSON before you commit it to the repository.

Frequently Asked Questions (FAQ)

What's the difference between formatting and validating JSON?↓
They really work together — this tool always validates the JSON first. If it's valid, it formats it for readability. If it's invalid, it immediately reports the line and column where the error is, which is much faster than scanning character by character.
Why would I want to minify JSON?↓
Minifying strips out unnecessary whitespace and line breaks, making the file smaller — ideal for sending real data through an API or storing in a config file that humans don't need to read. Formatting does the opposite: it adds indentation to make the file easier for humans to read, at the cost of a larger file.
Why does the tool say my JSON is invalid when it looks fine?↓
The most common causes are a trailing comma before a closing bracket, using single quotes (') instead of double quotes ("), or including a comment in the file — all valid in a JavaScript object literal, but not in standard JSON. This tool checks strictly against the JSON spec.
How large a JSON file does this support?↓
There's no hard size limit, since it's processed directly with the browser's JSON.parse. Very large JSON (tens of megabytes) may make the browser slower, but it handles typical JSON used in web development and APIs without issue.
Is the JSON I paste sent to a server?↓
No data ever leaves your device. All validation and formatting runs entirely in your browser, so it's safe to use with sensitive data like API responses or config files containing secrets.

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