JSON Formatter
Paste messy or minified JSON and get it formatted, indented, and validated in your browser. If the JSON is broken, it points you to the problem instead of failing silently. Nothing you paste is uploaded - the parsing happens locally.
Formatting and validation are two jobs
Formatting (or 'pretty-printing') adds the indentation and line breaks that make a nested structure readable. Validation checks that the text is actually legal JSON - every key quoted, commas in the right places, brackets balanced. A formatter that also validates saves you from the most common API headache: a response that looks fine but will not parse because of a stray trailing comma or a single quote where a double quote belongs.
Because JSON is strict, small mistakes break the whole document. The tool reads the structure top to bottom and stops at the first illegal character, which is usually right next to the real error.
Reading and using the output
Once formatted, the shape of the data is obvious: objects nest, arrays line up, and you can see where a field actually lives.
- Use it to inspect an API response before writing code against it.
- Minify in reverse when you need the smallest payload for production.
- Copy a clean version into documentation or a bug report so others can read it.
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FAQs
Is my JSON sent to a server?▼
No. Parsing and formatting run entirely in your browser with JavaScript, so the data never leaves your device. This makes it safe for API responses or config that contain sensitive values.
Why does it say my JSON is invalid?▼
JSON has strict rules. The usual culprits are a trailing comma after the last item, single quotes instead of double quotes, unquoted keys, or a missing bracket. The error message points to where parsing failed, which is normally right at or just before the mistake.
What is the difference between JSON and a JavaScript object?▼
JSON is a text format with stricter rules: keys must be double-quoted, no trailing commas, no comments, and no functions or undefined values. A JavaScript object is more relaxed. Valid JSON is almost always a valid JS object, but not the reverse.
Can it handle very large files?▼
It can format large documents, but extremely large files (tens of megabytes) may slow your browser because everything is held in memory. For huge data, a streaming parser in code is better suited.
Does it preserve the order of my keys?▼
Yes. The formatter keeps keys in the order they appear. JSON itself does not guarantee order to consumers, but the tool will not reshuffle your data.
What does 'minify' do?▼
Minifying removes all the optional whitespace - spaces, indentation, and line breaks - to produce the smallest valid JSON. It is what you send over the network in production; you format it back to readable form when debugging.
Why are trailing commas not allowed?▼
The JSON specification forbids them. A comma after the last element of an array or object is valid in modern JavaScript but invalid JSON, and it is one of the most frequent parse errors. Remove it and the document validates.
Can I format JSON with comments?▼
Standard JSON does not allow comments, so a document with // or /* */ will fail validation. Some config formats (JSONC, JSON5) permit them, but those are not plain JSON. Strip comments to get valid JSON.
Does it change my numbers or dates?▼
No. It treats numbers and strings exactly as written. Note that JSON has no date type - dates are just strings - so the tool leaves them untouched.
How do I fix deeply nested JSON that is hard to read?▼
Format it first to expose the structure, then collapse or focus on the branch you care about. If a single object is enormous, copy out the sub-section you need and format that on its own.
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