JSON Formatter
Beautify, validate, and clean up JSON data in your browser.
Format JSON instantly in your browser. Paste a payload, tidy the structure, and copy or download the result without affecting the data itself.
What is this tool?
JSON is the standard text format for structured data in APIs, configuration files, and browser-based applications. When payloads are minified or generated automatically, they can become difficult to inspect by eye. A JSON formatter adds indentation and line breaks so developers can read, compare, and debug structures quickly. It is especially useful when reviewing API responses, config values, or application payloads from a server or test environment.
Example
Compact JSON
Original input
{"name":"Cassidor","active":true,"roles":["dev","ops"]}Formatted JSON
Clean, readable output
{
"name": "Cassidor",
"active": true,
"roles": [
"dev",
"ops"
]
}Why use Cassidor?
- Runs entirely in your browser so the data stays local.
- Helps during API debugging and config review.
- Includes copy and download actions for quick reuse.
Frequently asked questions
What is JSON formatting?
JSON formatting adds indentation and line breaks so the structure is readable without changing the meaning of the data.
Why is my JSON invalid?
Most invalid JSON issues come from missing commas, trailing commas, unquoted keys, or mismatched brackets.
Does formatting change the data?
No. It changes the presentation, not the underlying values or keys.
Can I format large JSON files?
Yes. The tool works best for typical API payloads and config files, and it is useful for reviewing large documents in a cleaner layout.
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