What is JSON?
Behind every weather app, shopping site, and map service, servers are constantly sending data to your device. Much of that data travels in a format called JSON — JavaScript Object Notation. Despite the technical name, the structure is simple: it is a list of label-and-value pairs, like a very organized set of notes. A person’s profile might include a name, an age, and a list of hobbies, all expressed together in one block.
Why do you need a formatter?
JSON data received from an API or system is almost always compressed onto a single line, with all whitespace removed to reduce file size. That is efficient for machines to read but nearly impossible for people to follow.
A JSON formatter spreads that compressed data across multiple lines and adds indentation so the structure becomes clear at a glance. It is a standard part of debugging and reviewing data.
The reverse also applies. Well-formatted JSON can be minified back into a single line before it is sent in production, reducing the amount of data transferred.
Common JSON errors
JSON follows strict rules. Small mistakes break the whole document.
The most frequent mistake is a trailing comma — a comma after the last item in a list or object. This is valid in JavaScript but not in JSON. The second most common issue is using single quotes instead of double quotes: JSON requires double quotes around all strings. The third is including comments: JSON does not support them.
The Validate button in this tool checks your input against these rules and reports exactly what went wrong when the format is invalid.
How to use this tool
Paste your JSON into the left panel. Format produces clean, indented output. Minify compresses it to one line. Validate checks the structure without changing the content.
You can choose between 2-space and 4-space indentation. The Copy button saves the result to your clipboard.
Frequently asked questions
What is the difference between JSON and XML? Both are formats for structured data. JSON is more compact and easier to read; XML requires opening and closing tags around everything, which makes the same data significantly longer. Most modern web APIs use JSON.
Is there a size limit? Processing happens inside your browser, so the practical limit is your browser’s available memory. Files up to a few megabytes are handled without issue. For very large files, a dedicated command-line tool will be faster.
Is my data sent to a server? No. Everything runs locally in your browser. Nothing you paste here leaves your device.