Formatera och Validera JSON-data Steg för Steg
Quick Answer
För att formatera JSON: klistra in din JSON i JSON Formatter och den beautifierade utmatningen med korrekt indentering visas omedelbart. För att validera: verktyget kontrollerar automatiskt syntax och visar ett fel med plats om ogiltig. All bearbetning sker lokalt.
Introduction
JSON (JavaScript Object Notation) är det vanligaste dataformatet för webb-API:er och konfigurationsfiler. Rå JSON från API:er är ofta minifierad till en enda rad, vilket gör den svår att läsa. Formatering (kallas beautifying eller pretty-printing) lägger till indentering och radbrytningar. Validering kontrollerar att JSON-syntaxen är korrekt —ett felplacerat kommatecken kan bryta hela din applikation.
Step by Step
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Open the JSON Formatter tool
Go to the JSON Formatter tool page. The tool accepts any JSON string as input — objects, arrays, or nested structures.
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Paste your JSON data
Paste the JSON you want to format or validate into the input textarea. This could be an API response, a config file, or a JSON string from your code.
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Review the formatted output
The tool parses your JSON and re-serializes it with 2-space indentation and line breaks. The formatted output appears instantly in the result field. If the JSON is invalid, an error message appears with the location of the syntax problem.
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Check validation status
If the JSON is valid, the tool shows a success indicator and the formatted output. If invalid, it displays the parse error — such as 'Unexpected token at position 42' — so you can fix the syntax issue in your source.
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Copy or minify the result
Use the Copy button to copy the formatted JSON to your clipboard. Some tools also offer a Minify button to remove all whitespace — useful for reducing payload size in production.
Examples
Format minified JSON
Input: {"name":"Alice","age":30,"roles":["admin","user"]}
Output: {
"name": "Alice",
"age": 30,
"roles": ["admin", "user"]
}
Detect invalid JSON (trailing comma)
Input: {"a":1,"b":2,}
Output: Error: Unexpected token } at position 11
Detect invalid JSON (single quotes)
Input: {'name':'Alice'}
Output: Error: Unexpected token ' at position 1
Common Problems
- Using single quotes for strings —JSON requires double quotes for all strings and keys.
- Trailing commas after the last item —JSON does not allow a comma before } or ].
- Comments in JSON —standard JSON does not support // or /* */ comments. Use JSONC or JSON5 if you need comments.
- Unquoted keys —unlike JavaScript object literals, JSON requires all keys to be in double quotes.
- Undefined, NaN, or Infinity values —JSON only supports null, not undefined or NaN.
Tips
- Always validate JSON before sending it in an API request —a syntax error can cause a 400 Bad Request response.
- Use minified JSON in production to save bandwidth, and formatted JSON in development for readability.
- JSON does not support Date objects —serialize dates as ISO 8601 strings (e.g., "2026-09-02T00:00:00Z").
- Use JSON.parse() in JavaScript to convert a JSON string to an object, and JSON.stringify() to convert an object to a JSON string.