JSON Formatter and Validator
Format, indent and validate JSON in your browser. Points out the error with line and column when the text is invalid.
How it works
JSON is the most widely used format for exchanging data between systems — API responses, configuration files and much more. But a single stray comma or a missing quote can break the whole thing. This tool solves the two most common problems: making JSON readable and checking whether it's valid.
Paste your content into the input field and choose an action. Format reorganizes the text with two-space indentation and line breaks, making the structure easy to read. Minify does the opposite: it removes every space and line break, producing the most compact version possible, ideal for sending less data.
If the JSON has a syntax error, validation reports the message and, when possible, the approximate line and column of the problem, so you can go straight to it instead of hunting for the error by eye. All processing happens locally, in your browser.
When to use
Developers use this tool constantly when working with APIs: a response arrives on a single compressed line and becomes impossible to read — formatting fixes it instantly. When building a request body or a config file, validating before saving avoids silent errors that would only show up in production.
It's also useful beyond pure development: analysts exporting data as JSON, people checking webhooks, or anyone who received a JSON file and just needs to understand what's inside. Minifying, in turn, is handy for pasting JSON into a size-constrained field or reducing the weight of a payload.
Practical examples
From one line to readable
An API returns something like this, all crammed together: {"id":1,"name":"Ana","active":true}. Formatting gives each field its own line with indentation, and it's immediately clear how many keys there are and how the data is nested.
Finding the error
If you paste {"name":"Ana",} with a trailing comma before the closing brace, validation flags the problem and points to the approximate position. Instead of rereading everything, you go straight to removing the extra comma.
Common mistakes
The most classic error is the trailing comma: placing a comma after the last item of an object or array. Many programming languages tolerate this, but pure JSON doesn't — and it's one of the most frequent causes of "invalid JSON".
Another common slip is using single quotes instead of double quotes. In JSON, both keys and text must be wrapped in double quotes; single quotes make the file invalid. The same goes for unquoted keys, which work in JavaScript objects but not in JSON.
There's also the confusion around special values: JSON accepts "true", "false" and "null", but not "undefined", comments (// or /* */) or functions. If your text contains any of those, validation will complain — and rightly so.
Frequently asked questions
Is my data saved anywhere?
No. The JSON is processed entirely in your browser and nothing is sent to or stored on servers. You can paste sensitive data with peace of mind.
What is the difference between format and minify?
Formatting makes the JSON readable, with line breaks and indentation. Minifying removes all spaces and breaks, producing the most compact version — useful for reducing data size.
Does the tool fix JSON automatically?
No. It validates and points out where the problem is, but fixing is up to you. That's intentional: automatic fixes could mask errors you need to know about.
Why does it show an error when my JSON looks correct?
Most often it's a trailing comma, single quotes instead of double, or unquoted keys. The error message usually indicates the line and column to help you locate it.
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