JSON Formatter, Validator & Fixer
Fix common issues, format, validate, and export your JSON data. Handles single quotes, comments, unquoted keys, MongoDB shell exports, and more automatically.
🚀 How it works
💡 Got errors? Try the "Fix & Format" button to auto-repair common JSON issues!
Input JSON
Formatted JSON
Auto-Fix Common Issues
Fixes single quotes, comments, unquoted keys, trailing commas automatically with one click.
Validate & Format
Instantly check syntax, beautify with indentation, and get detailed error messages.
Export & Download
Copy minified for production, download as .json file, or copy formatted version.
Lightning Fast
Real-time processing, works offline, handles large JSON files up to 10MB instantly.
Common JSON Issues We Fix
Single Quotes
{'name': 'John'}JSON requires double quotes around strings.
Trailing Commas
{"name": "John",}JSON doesn't allow trailing commas after the last item.
Comments
// Comment
/* Comment */JSON doesn't support comments - they must be removed.
Unquoted Keys
{name: "John"}Object keys must always be quoted in JSON.
Multi-line Strings
"Line 1
Line 2"Strings must be on single lines with \\n for breaks.
All Fixed!
{"name": "John"}Clean, valid JSON ready to use in your applications.
Click "Sample" above to see all these issues in action, then use "Fix & Format" to see the magic!
Understanding JSON Formatting
Pretty-Printing vs Minifying
The same JSON document can be written two ways without changing its meaning. Pretty-printing (beautifying) adds line breaks and indentation so the structure is easy for a human to read and debug: each nested object and array sits on its own indented level. Minifying strips every optional space and newline to produce the smallest possible payload, which is what you want when sending data over the network or embedding it in a build. Both forms parse to exactly the same object, so it is common to develop against the formatted version and ship the minified one. This tool gives you both: use the indent selector and Format to beautify, or Copy Minified to grab the compact version.
Validation and Why It Matters
Validation checks that your text obeys the JSON grammar defined in the ECMA-404 standard: strings wrapped in double quotes, keys always quoted, values limited to strings, numbers, booleans, null, objects and arrays, and no trailing commas or comments. A single stray character can make an entire file unparseable, and the resulting error is often reported far from the real mistake. When you format here, the document is parsed on our server and any syntax error is returned with a message so you can locate the problem, while the minify and download actions run in your browser on the already-validated result.
Where JSON Trips People Up
Most invalid JSON comes from confusing it with JavaScript object literals. JavaScript happily accepts single quotes, unquoted keys, trailing commas, and // comments, but strict JSON rejects all of them. Other frequent culprits are NaN or Infinity as numbers, unescaped line breaks inside strings, and a byte-order mark hiding at the start of a file. The Fix & Format button repairs the common JavaScript-flavored mistakes automatically, converting them to valid JSON in one step.
Frequently Asked Questions
Is JSON the same as a JavaScript object?
They look similar but are not identical. JSON is a strict text format: keys and strings must use double quotes, and comments, trailing commas, and single quotes are not allowed. A JavaScript object literal is more relaxed. Pasting a JS object here and using Fix & Format converts it into valid JSON. The same goes for MongoDB shell output: wrappers like ISODate(), ObjectId(), and NumberInt() are converted to their plain JSON values.
What is the difference between formatting and minifying JSON?
Formatting adds indentation and line breaks so the data is easy to read and debug. Minifying removes all unnecessary whitespace to make the file as small as possible for transmission or storage. Both produce identical data when parsed. Only the presentation differs.
Does formatting change my data?
No. Beautifying and minifying only adjust whitespace and indentation. Keys, values, ordering within arrays, and data types are all preserved, so the parsed result is exactly the same object you started with.
Why does my JSON fail validation even though it looks fine?
Common hidden causes include a trailing comma after the last item, single quotes instead of double quotes, unquoted object keys, comments, or an invisible byte-order mark at the start of the file. The error message returned when you format points you toward the offending location.
Can this handle large JSON files?
Yes, it comfortably handles files up to about 10MB. The formatting and validation are performed on our server, and the copy-minified and download actions run locally in your browser.
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