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Best Practice Beginner 1 min read 268 words

JSON Formatting and Validation: Best Practices for Clean Data

Best practices for formatting, validating, and structuring JSON data. Covers indentation standards, JSON Schema validation, common syntax errors, and the differences between JSON and JSON5.

Key Takeaways

JSON has a single universal syntax — no competing standards or flavors.
Trailing comma**: `{"a": 1,}` — invalid in JSON (valid in JS/JSON5)
JSON Schema defines the expected structure, types, and constraints of your JSON data.
JSON5 relaxes JSON's strict syntax — allowing comments, trailing commas, single quotes, and unquoted keys.
For data interchange, always use standard JSON.

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JSON Formatting Standards

JSON has a single universal syntax — no competing standards or flavors. Yet formatting varies widely: minified for production, pretty-printed for debugging, and sorted keys for deterministic output. Consistent formatting prevents unnecessary diff noise in version control.

Formatting Conventions

Convention	When	Benefit
2-space indent	Most codebases	Compact, readable
4-space indent	Python ecosystems	Extra readability
Sorted keys	Config files, snapshots	Deterministic diffs
Minified	API responses, storage	Minimal size
One item per line	Arrays of objects	Clean diffs

Common Syntax Errors

Trailing comma: {"a": 1,} — invalid in JSON (valid in JS/JSON5)
Single quotes: {'a': 1} — invalid, must use double quotes
Unquoted keys: {a: 1} — invalid, keys must be quoted strings
Comments: // comment — not allowed in JSON
Infinity/NaN: Not valid JSON values

JSON Schema Validation

JSON Schema defines the expected structure, types, and constraints of your JSON data. It catches type errors (string where number expected), missing required fields, and invalid enum values before they cause runtime failures. Use schemas for API request/response validation and configuration file validation.

JSON5 and Alternatives

JSON5 relaxes JSON's strict syntax — allowing comments, trailing commas, single quotes, and unquoted keys. It is popular for configuration files that humans edit directly. For data interchange, always use standard JSON.

Format, validate, and transform JSON with the Peasy JSON tools — supports pretty-printing, minification, sorting, and JSON Schema validation.