Practical example
An API response such as {"price":"19.90","active":"false"} is valid JSON, but the quoted number and boolean may still break consumers that expect strict types.
JSON Formatter
What is JSON?
JSON (JavaScript Object Notation) is a lightweight data format used to exchange structured data between services and applications.
This tool helps you format (pretty-print) JSON for readability or minify JSON to reduce size for storage and network transfer. Processing runs locally in your browser.
How to use the JSON Formatter
- Paste your JSON into the Input field.
- Click Format to pretty-print JSON with indentation.
- Click Minify to remove whitespace and shrink the JSON.
- Use Copy to copy the result.
Common JSON formatting errors
- Trailing commas are not valid in standard JSON.
- Keys and string values must use double quotes.
- Unescaped quotes inside strings will break parsing.
- Missing commas between fields or array items.
JSON debugging workflow
Format before reading
Pretty-print the payload first so nested arrays, objects, nulls, and escaped strings are easy to inspect.
Separate syntax from data shape
Valid JSON can still be wrong for an API contract. After formatting succeeds, validate required fields, types, and enums with a schema.
Check copied responses
If formatting fails, confirm the response is really JSON and not an HTML error page, truncated output, or log wrapper.
Minify only after validation
Minified JSON is useful for transport and config files, but keep a formatted version while debugging changes.
Related guides
Learn the workflow behind this tool and what to check next.
API debugging
How to debug an API JSON response step by step
A repeatable workflow for separating transport errors, JSON syntax problems, and data-contract failures in API responses.
Read guide
APIs and data
How to debug JSON API payloads
A practical workflow for formatting JSON, finding syntax errors, validating payload shape, and checking response status when API data looks wrong.
Read guide
JSON checks before you debug an API response
Formatting is only the first step. Use the formatted output to confirm structure, types, nesting, and whether the response can be copied into tests or documentation.
Validate structure
Check missing commas, trailing commas, unescaped quotes, duplicate-looking fields, and deeply nested arrays before blaming the API client.
Compare expected types
Look for strings that should be numbers, null values that your app cannot handle, and booleans represented as text.
Prepare fixtures
Minify payloads for compact fixtures or format them for readable code reviews, bug reports, and API docs.
Remove private data
Replace tokens, emails, customer IDs, and real records with safe sample values before sharing JSON in tickets or chats.
A practical example, an edge case, and a maintainer note
Edge case
A response beginning with <html> is usually a proxy or application error page, not malformed JSON. Check the HTTP status and Content-Type first.
Maintainer note
I use formatting to reveal structure, then validate the data contract separately; readable JSON is not automatically correct JSON.
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JSON Formatter FAQ
Does this tool validate JSON?
If your input is invalid JSON, the formatter will show an error. After formatting succeeds, the output is valid JSON.
Is my JSON sent to the server?
No. Formatting happens in your browser. We do not store or transmit your input.
What’s the difference between JSON and JavaScript objects?
JSON is a data format with strict rules (double quotes, no functions). JavaScript objects are more flexible and allow additional syntax.
Can I format huge JSON files?
Large inputs may be slow depending on your device. For very large files, try splitting the JSON or formatting smaller parts.