JSON Formatter & Validator
Beautify, minify, and validate JSON with live error reporting that pinpoints the exact line and column, plus a collapsible tree view for navigating large documents — all in your browser.
Interactive Client Prototype Sandbox
Editable — type or paste JSON, then Beautify to format.
Disclaimer: This free tool is provided “as is,” without warranties of any kind, and is for general informational purposes only — not professional, legal, financial, medical, tax, or engineering advice. Results may contain errors; verify anything important independently and use at your own risk. We accept no liability for any loss or damage arising from its use. See our Terms of Use for details.
Step-by-Step Guide
Paste raw or minified JSON, pick your indentation, and click Beautify or Minify. Invalid JSON is flagged with the exact line and column and a caret marking the spot. Switch to Tree view to expand and collapse nested nodes. All parsing happens in your browser.
Input '{"a":1,}' ➔ Beautify ➔ flagged at the trailing comma with its line and column; fix it and it reformats and shows a collapsible tree.
Who it's for
Software developers, DevOps engineers, systems administrators, data scientists, and students.
Core Features
- Format with your choice of indentation (2, 4, or 8 spaces).
- Validator pinpoints the exact line and column with a caret under the offending character.
- One-click minify to pack JSON onto a single line.
- Collapsible tree view to expand and collapse nested objects and arrays.
🛡️ No tracking — your inputs, keys, and details never leave this client sandbox.
Related tools
How do I fix a JSON syntax error?
Click Beautify and the tool reports the exact line and column of the problem with a caret pointing at the offending character — usually a missing comma, an extra trailing comma, an unquoted key, or single quotes where double quotes are required. Fix the spot it marks and format again until it reads as valid.
Does it validate JSON?
Yes. Every time you format or minify, the input is parsed; if it's well-formed you get a "syntactically valid" confirmation, and if not you get the exact parser error. It checks JSON syntax, not whether the data matches a particular schema.
What's the difference between beautify and minify?
Beautify re-indents your JSON across multiple lines (2, 4, or 8 spaces) so it's readable. Minify strips all whitespace onto a single line to make the payload as small as possible — handy for embedding or sending over the wire.
How does the tree view work?
Switch to Tree view to see your JSON as a collapsible outline: click any object or array to expand or collapse it, and values are color-coded by type. The top levels open by default and deeper nodes start collapsed, so large documents stay readable. The tree is a read-only inspector — edit the JSON in Text view.
Is my JSON uploaded anywhere?
No. Parsing, formatting, and validation all run in your browser. Nothing you paste is sent to a server, so you can safely format config files or API responses that contain sensitive values.
Can I format JSON with comments (JSON5 or JSONC)?
Standard JSON forbids comments — any // or /* */ comment causes a parse error and the validator will flag it. If you are working with JSON5 or JSONC (used by VS Code settings files and some config formats), strip the comments first before formatting. The tool validates against strict RFC 8259 JSON, not JSON5 or JSONC extensions.
Why does my large integer look wrong after formatting?
JavaScript's Number type is a 64-bit IEEE 754 float, which cannot represent integers larger than 2^53 exactly (about 9 quadrillion). If your JSON contains very large integer IDs — common in some database systems and financial APIs — they may lose precision when the formatter parses and re-serializes them. The safe approach is to represent those values as strings in your JSON schema. The tool shows the parsed value exactly as JavaScript sees it, which may differ from the original for extreme integers.
JSON in the real world
Every time a developer opens a browser's network tab and finds a wall of text like {"id":1,"name":"Alice","roles":["admin","editor"],"meta":{"created":"2024-01-15","active":true}} — all on a single line with no whitespace — their first instinct is to paste it somewhere that makes it readable. That paste-and-format reflex happens dozens of times a day across any team working with APIs, webhooks, or configuration files. JSON's deliberate compactness (no unnecessary whitespace) is a feature for transmission but a liability for human inspection. A formatter converts the machine-optimized form into the indented, line-per-entry form that a human can actually read and debug.
Why formatting matters
Minified JSON is a single line of text with no whitespace — ideal for transmission because it is as small as possible, but unreadable for humans. Formatted (or 'pretty-printed') JSON adds consistent indentation so the tree structure is visible: nested objects are indented one level deeper than their parents, and each key-value pair occupies its own line. When debugging an API integration, a failed webhook, or a configuration file, a formatted view is usually the first diagnostic step.
Validation and the most common errors
A JSON formatter doubles as a validator because any formatter must parse the input before it can re-emit it. The most frequent errors are: a trailing comma after the last element of an array or object (valid in JavaScript but explicitly forbidden by the JSON spec), single-quoted strings (JSON requires double quotes), unquoted property keys, and comments (JSON has no comment syntax, unlike JSON5 or YAML). Pinpointing the exact line and column — rather than just saying 'invalid JSON' — saves significant debugging time on large documents.
Common mistakes: large integers and comments
Two classes of errors catch developers off guard. First, JavaScript's Number type is a 64-bit IEEE 754 float, which cannot represent integers larger than 2^53 exactly. If your JSON contains very large integer IDs — common in some database systems — they may lose precision when the formatter parses and re-serializes them. The safe approach is to represent those values as strings. Second, JSON has no comment syntax. Files with // or /* */ comments — common in JSONC (VS Code settings) and JSON5 — will fail strict RFC 8259 parsing. Strip comments before formatting, or use a tool that understands JSON5 explicitly.