JSON Formatter & Validator
Pretty-print, minify, and validate JSON with line-precise errors.
Browser onlyYour data never leaves this device.
Runs entirely in your browser. Your JSON never leaves this device and is never stored.
Details: Privacy policy
Input
Parsed as data only — never executed.
Result
No input yet.
Paste JSON above to validate it.
JSON Formatter & Validator parses, cleans, formats, and compresses JSON data payloads instantly while pinpointing syntax flaws with line and column precision. Unlike JSON Tree Viewer, which visualizes complex data structures into collapsible hierarchical branches for visual exploration, JSON Formatter focuses on textual fidelity, producing standard two-space indented code for effortless reading or compact single-line minification to minimize network payload size. The tool adheres strictly to standard JSON.parse semantics rather than permissive JSON5 extensions: comments and trailing commas are refused outright and flagged as syntax errors with exact 1-based line and column offsets. When encountering duplicate object keys, the parser follows the official ECMAScript specification by retaining the last declared value. Built-in sanitization scrubs sensitive user input from parser exception strings, exposing only helpful error reasons without echoing confidential snippets to the screen. Operating under an in-memory boundary of 200,000 characters, all validation, indentation, and minification execute entirely inside your local browser tab, ensuring sensitive API tokens and internal server responses never upload to remote servers.
Key facts
- Input
- JSON
- Output
- Indented or minified JSON
- Limits
- Input text is capped at 200,000 characters per formatting and validation pass. Error locations represent 1-based line and character offsets computed from parser cursor positions.
- Processing
- In your browser — nothing is uploaded
- Sign-up
- Not required
- Cost
- Free
Limits above are read from the same code that enforces them; formats are the ones the tool accepts and produces.
How to use JSON Formatter & Validator
- Paste or type raw JSON data into the input editor (up to 200,000 characters).
- Select Pretty-printed for indented structure or Minified for single-line compression.
- Review the real-time validator status to verify standard JSON grammar.
- Locate any reported syntax issues using the specific 1-based line and column pointers.
- Click Copy formatted JSON or Download JSON to export your structured formatted.json file.
- Click Clear input to wipe the editor and prepare for a new JSON payload.
What you get
- Pretty-printed JSON, or minified JSON when that is what you need.
- A validation verdict with the failure offset, so a syntax error can be found rather than guessed at.
- Specification-faithful parsing: no comments, no trailing commas, and duplicate keys keeping their last value.
When to use JSON Formatter & Validator
- Readable-ify a minified API response before debugging it.
- Locate the exact position of a syntax error in a config file.
- Check a config file pasted from a ticket before it reaches a deploy, where a trailing comma is the usual culprit.
Frequently asked questions about JSON Formatter & Validator
Does JSON Formatter upload or log my data?
No. All parsing, validation, and serialization execute locally within your browser's JavaScript environment; no payload bytes ever touch an external network.
What is the maximum JSON payload size supported?
The tool processes JSON text up to 200,000 characters in a single operation, safeguarding your browser tab against memory exhaustion.
How does JSON Formatter differ from JSON Tree Viewer?
JSON Formatter outputs clean indented text or minified strings for editing and code insertion, whereas JSON Tree Viewer renders an interactive collapsible node tree for exploratory data inspection.
Why does the validator reject comments and trailing commas?
Standard RFC 8259 JSON prohibits comments and trailing commas; the validator strictly follows this standard to guarantee compatibility with all external backend APIs.
What happens if an object contains duplicate keys?
In accordance with ECMAScript JSON parsing specifications, duplicate keys within the same object do not fail validation; instead, the parser retains only the last encountered key-value pair.
Guides that compare JSON Formatter & Validator
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