JSON Validator
Validate JSON instantly with precise error messages. Get exact line and column numbers for any syntax errors.
JSON Validation Tips
Common pitfalls and how to catch them before they break your application.
Validate Early in Your Development Workflow
Don't wait until deployment to validate JSON. Check configuration files, API response mocks, and fixture data during development. Catching syntax errors early saves debugging time later.
Watch Out for Trailing Commas
Unlike JavaScript, JSON does not allow trailing commas after the last item in an array or object. This is the most common JSON syntax error — use Auto-Fix to remove them instantly.
Always Use Double Quotes
JSON requires double quotes for both keys and string values. Single quotes, unquoted keys, and backtick templates are JavaScript features that are not valid in JSON.
Check for Duplicate Keys
JSON technically allows duplicate keys, but their behavior is unpredictable — different parsers handle them differently. Always ensure each key in an object is unique to avoid unexpected data loss.
Validation Features
Catch every JSON error with precise diagnostics.
Real-Time Validation
JSON is validated as you type with instant feedback. Errors are highlighted directly in the editor.
Precise Error Location
Get exact line and column numbers for syntax errors. Click the error to jump directly to the problem.
Auto-Fix Support
Common errors like trailing commas, single quotes, and unquoted keys can be fixed automatically.
What is JSON Validation?
JSON validation checks whether a string is syntactically correct JSON according to the JSON specification (json.org). Valid JSON must follow strict rules: double-quoted strings, no trailing commas, no comments, and proper nesting of objects and arrays.
Common JSON Errors
{ name: "Alice" }
Keys must be double-quoted, e.g. "name"
{ "a": 1, "b": 2, }
Trailing commas are not allowed in JSON
{ "name": 'Alice' }
Strings must use double quotes, not single quotes
JSON Validator FAQ
What JSON errors can it detect?
It detects all JSON syntax errors including missing commas, unclosed brackets, invalid values, duplicate keys, trailing commas, and more.
What can Auto-Fix repair?
Auto-Fix handles trailing commas, single quotes to double quotes, unquoted keys, JavaScript comments, BOM characters, and JS literals like undefined/NaN/Infinity.
Is validation done locally?
Yes, all validation happens in your browser. No data is sent to any server.
Why is my JSON showing as invalid?
The most common causes are: trailing commas after the last item, single quotes instead of double quotes, unquoted property keys, JavaScript comments (// or /* */), and undefined/NaN values. Use the Auto-Fix button to resolve many of these automatically.
Can this validator check JSON against a schema?
This tool validates JSON syntax only. To validate JSON data against a JSON Schema (checking types, required fields, constraints), use our dedicated JSON Schema Validator tool.
Does it support JSON5 or JSONC (JSON with comments)?
JSON5 and JSONC are not valid JSON per the RFC 8259 specification. However, the Auto-Fix feature can strip comments, convert single quotes, and fix other non-standard syntax to produce valid JSON.
Is my data safe when validating?
Completely safe. All validation runs locally in your browser using JavaScript. Your JSON data never leaves your device — no server requests, no logging, no third-party access.
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Fix Invalid JSON Online
Paste broken JSON and get it fixed automatically. Handles trailing commas, single quotes, comments, unquoted keys and other common syntax mistakes.
JSON Parse Error?
Pinpoint and fix JSON.parse() errors instantly. See the exact line, column and cause of every syntax error — then auto-repair with one click.
JSON Schema Validator
Validate JSON data against a JSON Schema. Get detailed error messages with exact paths for any violations.
JSON Diff
Compare two JSON documents side by side. Instantly spot additions, removals, and changes with color-coded diff highlighting.