JSON Validator
Validate JSON syntax against RFC 8259 with exact line and column diagnostics and one-click auto-fix for trailing commas and comments.
Local Workspace (json-utility)
How to Use JSON Validator
- 1Paste the JSON or JSONC configuration file you want to inspect into the Input JSON pane (or click Load JSONC Sample).
- 2Check the RFC 8259 Status card and the syntax error banner for the exact 1-based Line and Column number and visual caret pointer (^).
- 3If comments or trailing commas are present, click Auto-Fix Comments & Trailing Commas to repair the payload into strict RFC 8259 JSON.
Technical Specifications & Guardrails
- Pinpoints exact 1-indexed Line and Column numbers via native parser positions and an RFC 8259 lexical scanner
- Renders a monospace code excerpt with a visual caret (^) pointing directly to the offending token
- String-aware Auto-Fix strips // and /* */ comments and trailing commas without corrupting URLs inside strings
- Executes inside a resilient Web Worker guarded by WorkerClient timeout recovery up to 10 MB
Practical Example: Repairing a VS Code tsconfig / JSONC Snippet for Strict Parsers
- Sample Input
- A configuration file containing // comments, /* block comments */, and trailing commas after the last array item that fails strict JSON.parse().
- Verified Local Output
- Pinpoints the exact comment/comma line and repairs the file into valid RFC 8259 JSON in one click while preserving 'https://...' URLs inside string values.
Operational Limits & Browser Guardrails
Validates payloads up to 10 MB against strict IETF RFC 8259 rules. Auto-Fix repairs JSONC comments (// and /* */) and trailing commas before } or ]; structural syntax errors such as unquoted keys, single-quoted strings, or missing colons are highlighted by line and column for manual correction.
Frequently Asked Questions
What errors can Auto-Fix JSONC repair automatically?
The string-aware repair scanner strips single-line (//) and multi-line (/* */) comments and removes trailing commas before closing braces (}) or brackets (]) while leaving '//' or '/*' sequences inside quoted string literals untouched.
Does the JSON Validator use eval() or new Function() to parse input?
No. Validation uses native JSON.parse() and a deterministic lexical scanner inside a local worker, never executing untrusted input as JavaScript code.
Why does RFC 8259 reject trailing commas and single quotes?
IETF RFC 8259 mandates double-quoted property names and forbids trailing commas to guarantee interoperability across C, Go, Rust, Python, and Java parsers.