Json5 Validator - Complete Guide

JSON5 validation checks extended JSON syntax that allows comments, trailing commas, unquoted keys, and other developer-friendly features. JSON5 is ideal for configuration files where human readability matters more than strict JSON compatibility.

How It Works

The validator parses JSON5 syntax, which extends JSON with: single and multi-line comments, trailing commas, unquoted object keys, single-quoted strings, hexadecimal numbers, and more. It reports errors while accepting valid JSON5 features.

Technical Details

JSON5 adds: // and /* */ comments, trailing commas in arrays/objects, unquoted keys (if valid identifiers), single-quoted strings, multi-line strings, hex numbers (0xFF), Infinity/-Infinity/NaN, and leading/trailing decimal points (.5, 5.).

Common Use Cases

1. Configuration Files: Config files with comments for documentation.
   • Example: VS Code settings use JSONC (similar to JSON5)
2. Development Settings: Babel, ESLint configs with comments.
3. Documentation Examples: JSON examples with explanatory comments.
4. Human-Edited Data: Data files that developers frequently edit.

Code Examples

JSON5 Features

{
  // Single-line comment
  name: 'John',          // Unquoted key, single-quoted value
  age: 30,               // Trailing comma OK
  /* Multi-line
     comment */
  hex: 0xFF,             // Hexadecimal
  infinity: Infinity,    // Special numbers
  'quoted-key': true,    // Quoted keys for special chars
}

JSON5 allows comments, trailing commas, unquoted keys, and other features not allowed in standard JSON.

Tips & Best Practices

• Use JSON5 for config files that need comments
• Convert to standard JSON for data exchange
• Use a JSON5 parser library for your platform
• Consider JSONC if you only need comments
• Document that files use JSON5, not standard JSON

Common Mistakes to Avoid

• Assuming all JSON parsers support JSON5
• Using JSON5 for API responses
• Forgetting JSON5 requires special parser
• Mixing JSON5 with tools expecting standard JSON

When to Use This Tool

Use JSON5 validation for configuration files, build tool settings, and any human-edited JSON that benefits from comments and relaxed syntax. Not for API data exchange.

Frequently Asked Questions

What's the difference between JSON5 and JSONC?

JSON5 allows more features (unquoted keys, trailing commas, single quotes). JSONC (JSON with Comments) only adds comments to standard JSON. VS Code uses JSONC. Choose based on what your parser supports.

Can I convert JSON5 to standard JSON?

Yes, JSON5 parsers output standard JavaScript objects that can be serialized to JSON. Comments and formatting are lost, but data is preserved.

Should I use JSON5 for APIs?

No, use standard JSON for APIs. JSON5 is for human-edited files. APIs should use strict, widely-supported JSON format.

Do browsers support JSON5?

Not natively. JSON5 requires a parser library. Only use JSON5 where you control the parsing environment (Node.js configs, build tools).

Get Started

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Last updated: June 27, 2026