JSON formatter and validator

Format, check and fix JSON in one place

JSON is the format most programs use to exchange data: API responses, configuration files, exports and logs. It is easy for machines and hard for people, especially when it arrives on a single line. This tool turns that line into readable, indented JSON, or does the opposite and minifies it to save space, and it tells you whether the JSON is valid at all.

Errors, explained in plain words

A typical parser says something like "Unexpected token } at position 214". Here you get the line and column, the surrounding lines with a marker under the problem, and an explanation such as "there is a comma before a closing brace". The mistakes that cause most invalid JSON are always the same ones:

• A trailing comma after the last item.
• Single quotes instead of double quotes.
• Property names without quotes, as in JavaScript objects.
• Comments, which JSON does not allow.
• A missing comma between two items.
• Python-style values such as True or None.

Automatic repair

When the JSON is broken but the intent is clear, the "Try to repair automatically" button fixes all of the above and tells you what it changed. It also removes the code fence that chat assistants wrap around JSON and turns curly quotes pasted from a document into normal ones. Review the result: a repair is a reasonable guess, not a guarantee.

It does not damage your data

Many formatters parse numbers into ordinary floating-point values, which quietly rounds very large numbers such as long identifiers. This tool keeps every number exactly as you wrote it. It also warns you about repeated keys, which are technically accepted but usually mean a mistake, because most programs keep only the last value.

Safe for sensitive data

API responses often contain tokens, emails or customer data. Because the work happens in your browser, nothing is sent to a server, and you can use the tool without giving that information to anyone.