Why is my JSON invalid?

The most common reasons for invalid JSON include missing or trailing commas, using single quotes instead of double quotes around keys/strings, unescaped special characters, unclosed brackets/braces, or comments (which are not permitted in standard JSON).

Can JSON start with an array or primitive?

Yes! According to the official JSON specification (RFC 8259), valid top-level JSON can be an Object, an Array, a String, a Number, a Boolean (true/false), or Null.

Is my JSON uploaded to any server?

No. All validation and analysis happen 100% locally in your web browser using JavaScript. No payload, API keys, or data are ever uploaded to any server.

Developer Tool

JSON Validator

Q: What is a JSON validator?

A JSON validator is a developer tool that analyzes JSON data against the official JSON specification (ECMA-404 / RFC 8259) to ensure that the syntax is strictly valid and free of errors before sending it to APIs, databases, or configuration systems.

Q: How do I validate JSON online?

Paste your JSON code into the editor or upload a .json file, then click 'Validate JSON'. The tool instantly indicates whether your JSON is valid or flags the exact line and column where an error occurred.

Validate JSON online for free. Check JSON syntax, find errors, and verify your JSON instantly in your browser. Your data never leaves your device.

Ctrl/⌘+Enter

JSON Document to Validate

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100% Client-Side Privacy: Your JSON is validated locally in your browser. No data is ever sent to any server.

What is a JSON Validator?

A JSON Validator is an essential online developer utility that checks whether a JSON document conforms strictly to official standard syntax rules (ECMA-404 / RFC 8259).

When developing REST APIs, configuring web applications, setting up CI/CD pipelines, or exchanging data across microservices, even a single syntax flaw (such as a missing comma, unquoted key, or trailing comma) can cause server errors, parsing exceptions, and application crashes. A JSON validator inspects the payload in real time, flags whether it is valid or invalid, and pinpoints the exact line and column number of any syntax mistake.

How to Validate JSON Online

Input Your JSON

Paste your JSON snippet into the editor, drag & drop a .json file, or click Upload File.

Click Validate JSON

Click the prominent Validate JSON button or press Ctrl+Enter.

Review Status & Errors

Check whether your JSON is valid. If invalid, review the highlighted line, column, and error explanation.

Fix, Copy & Download

Fix any syntax errors directly in the editor, copy the validated code, or download it as validated.json.

Common JSON Syntax Errors & How to Fix Them

Missing or Trailing Commas

Properties in an object must be separated by commas, but having a comma after the last property is illegal in standard JSON.

// Invalid (trailing comma): { "name": "Alice", "age": 25, }

Single Quotes Around Keys / Strings

JSON strictly requires double quotes (") for all property names and string values. Single quotes (') are invalid.

// Invalid (single quotes): { 'title': 'Developer' }

Unquoted Property Names

Unlike regular JavaScript object literals, JSON requires all key names to be wrapped in double quotes.

// Invalid (unquoted key): { id: 101, status: "active" }

Unclosed Braces or Brackets

Every opening curly brace { must have a matching closing brace }, and every opening bracket [ must close with ].

// Invalid (missing closing brace): { "users": ["Alice", "Bob"]

Key Features of This JSON Validator

Strict ECMA-404 Validation

Verifies compliance with official JSON standards to ensure seamless compatibility with APIs and databases.

Line & Column Diagnostics

Pinpoints the exact location of syntax errors, highlighting the problem line with code snippet previews.

Root Type & Structure Analysis

Identifies root value types (Object, Array, Primitives) and displays metrics like keys, objects, and depth.

Presets & Examples

One-click buttons to load valid complex structures or intentionally invalid examples for quick testing.

100% Client-Side Privacy

Zero server uploads. Your confidential data, passwords, and sensitive API payloads never leave your browser.

File Upload & Drag-and-Drop

Directly drag and drop .json files into the validation editor for rapid validation of large files.

Frequently Asked Questions

What is a JSON Validator?

A JSON Validator is a tool that verifies whether a given text strictly adheres to JSON syntax specifications. It parses the data and checks for syntax violations like missing punctuation, invalid types, or misplaced characters.

How do I validate JSON online?

1. Paste your JSON text into the editor, drag & drop a .json file, or click 'Upload File'. 2. Click the 'Validate JSON' button (or press Ctrl/Cmd + Enter). 3. If valid, you will see a green confirmation with root type and document metrics. 4. If invalid, the validator highlights the exact line number, column number, and error reason.

What are the most common JSON syntax errors?

• Trailing commas after the last item in an object or array (e.g. {"a": 1,}). • Using single quotes instead of double quotes for property names or strings. • Unquoted property names (keys must always be in double quotes). • Unmatched or missing closing braces } or brackets ]. • Inclusion of JavaScript comments (// or /* */) which are disallowed in JSON.

Can JSON start with an array or string?

Yes. In modern JSON specifications (RFC 8259 / ECMA-404), valid JSON is any valid JSON value, which includes Objects ({...}), Arrays ([...]), Strings ("..."), Numbers (42), Booleans (true/false), and null.

Is my JSON data kept private and secure?

Yes, 100%. The validator runs entirely in your web browser using client-side JavaScript. None of your JSON payload, tokens, or files are uploaded to any server or shared with any third party.

Can I validate large JSON files?

Yes. You can drag and drop or upload .json files directly. Since parsing is handled in-memory by your browser's optimized V8 engine, it validates large JSON files quickly.