JSON Formatter. Validate, losslessly format, and minify JSON while flagging duplicate members and precision-sensitive numbers before parsed tree or XML views.
Choose your path
Validate, format or minify one JSON text without silently changing duplicate members or precision-sensitive number lexemes, while clearly separating parsed convenience views from lossless evidence.
Make a large response readable without changing identifiers, decimals or duplicate-member evidence.
Paste or load the bounded payload, validate it, inspect interoperability warnings, format losslessly and save the exact result to the API record.
Can diff input/output and prove that whitespace changed while number lexemes and duplicate members did not.
See duplicate names, unsafe integer/precision risks and parser limitations before approving a contract.
Validate adversarial and boundary samples, compare lossless text with parsed tree/XML views, and keep warnings in the Project record.
Does not mistake JSON.parse last-member behavior or IEEE-754 conversion for the sender’s exact data.
Operate validation, formatting, copying, download and Project save with named controls and contained editors.
Navigate labels/actions, read errors and warnings, then copy or save the result without relying on color alone.
Completes the exact task with no unnamed control, cropped editor or ambiguous status.
Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.
This tool is part of these guided projects. Each project provides step-by-step instructions with checklists and all the tools you need in one place.
Tools you might need next
Validate RFC 8259 JSON syntax with line hints, duplicate-member and precision warnings, plus an explicit schema and API-contract boundary.
Minify JSON. Remove whitespace. Reduce file size. For production and APIs. Free developer utility that runs locally in your browser — fast, private, and no
Compare two JSON objects and highlight differences. Find added, removed, and changed fields. Free developer utility that runs locally in your browser — fast
The default formatter tokenizes valid JSON and changes whitespace only, preserving string and number lexemes, member order, and duplicate members. Key sorting is skipped when duplicate names or precision-sensitive numbers are present.
The formatter validates JSON against RFC 8259 standard. It detects common issues like trailing commas, single quotes, unquoted keys, and comments (which are not valid JSON).
Source: IETF RFC 8259
Lossless minification removes insignificant JSON whitespace while preserving every string, number token, member, and array item. It does not certify a payload contract, canonicalize JSON, or make ambiguous duplicate members interoperable.
Updated: July 2026
Paste a minified API response to see its structure clearly. Useful when debugging REST APIs or inspecting network responses.
→ Formatted, indented JSON with syntax highlighting
Format a messy package.json or tsconfig.json with consistent indentation before committing to version control.
→ Clean, readable config with 2-space indentation
A developer receives a compressed JSON webhook body from Stripe or GitHub and formats it to trace nested event fields.
→ Expanded tree with clear key-value hierarchy for debugging
JSON requires double quotes for all strings and keys. Use: {"key": "value"} not {'key': 'value'}
JSON does not allow trailing commas. Remove the comma after the last element: [1, 2, 3] not [1, 2, 3,]
Validate and reformat JSON without silently normalizing exact number tokens or discarding duplicate object members. Parsed tree, key sorting, and XML remain convenience views with explicit interoperability boundaries.