What it does
Useful, focused capabilities
- Strict custom JSON parser
- Line and column diagnostics
- Duplicate-key detection or rejection
- Format, minify, and recursive key sorting
- Safe text-only tree renderer
Developer utilities · browser-local
Format, validate, minify, and inspect JSON
Validate, format, minify, sort, inspect, search, copy, and download JSON locally with line and column errors and optional duplicate-key rejection.
Work happens in the current browser. The route does not require an account or a server-side processing job.
Interactive browser workspace
JSON formatter and validator
The live tool is loaded in this browser only. This route does not need camera, microphone, or screen-capture permission for its main task.
Load the interactive workspace →Browser compatibility
Requirements and honest fallbacks
JavaScript and the File API for optional local JSON input and download.
- JavaScript
- File API
- download support
Questions people ask
Clear answers and limits
Does the tool use eval?
No. It uses a strict parser and renders values with DOM text nodes; input is never executed as code or injected as HTML.
Why are comments rejected?
Comments are not part of the JSON standard. Use JSON5 or another format when comments are required.
What happens to duplicate keys?
The validator reports them. Standard object construction keeps the last value unless the reject-duplicates option is enabled.
Does sorting change arrays?
No. Arrays retain order. Sorting applies recursively to object keys only.
Can it validate a JSON Schema?
Not in this route. It validates syntax and structure, not an external schema contract.
How to use this tool
Format, validate, minify, and inspect JSON entered in the browser, with syntax position, duplicate-key, line, column, and search feedback where supported. The text stays local to the current session. A valid parse does not prove that a schema, API, security policy, or receiving service will accept the JSON.
What to choose and what you get
What to choose
- pasted JSON text
Result
- formatted or minified JSON with syntax, line, column, duplicate-key, and search feedback
Supported formats
- Accepted formats: plain text.
- Output formats: JSON, HTML report.
Browser support and permissions
- Modern browser with JavaScript; clipboard, DOM, and download behavior varies by browser.
- No camera, microphone, or screen permission is needed.
Worked example
A pasted API example fails to parse and needs the exact syntax line, duplicate keys and a formatted local view.
Starting facts
- The JSON text remains in the browser.
- Formatting cannot repair ambiguous or semantically incorrect data automatically.
Observed operation: Parse the text, report line and column feedback, flag duplicate keys and produce formatted or minified output when valid.
Review the result: Inspect duplicate-key warnings and compare the formatted structure with the intended schema before copying it.
Boundary: Syntactic validity does not prove schema compliance, safe values, business correctness or trustworthiness of the data.
Check your result
- Strict custom JSON parser
- Line and column diagnostics
- Duplicate-key detection or rejection
Things to know
- Preserves JSON numeric and string spellings without rounding; downstream applications may still have numeric limits. Duplicate keys are preserved with a warning unless rejection is enabled.
Privacy boundary
Entered text stays in the current browser session and is not sent to an Aftermath processing service. How local processing is verified.
What this tool verifies
Checks the displayed limits and reports or creates formatted or minified JSON with syntax, line, column, duplicate-key, and search feedback from pasted JSON text.
Check before sharing
The result describes the text entered in this browser; it is not an external certification.
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