JSON Validator — Check JSON Syntax Online
Validate your JSON data against the RFC 8259 specification. Get instant error messages with line numbers pointing to the exact location of syntax issues.
Common JSON Syntax Mistakes
The most frequent errors developers encounter are trailing commas after the last item in an array or object, using single quotes instead of double quotes, and forgetting to quote object keys. JavaScript allows all of these, but strict JSON does not. This validator highlights the exact character position so you can fix issues instantly.
Validating API Responses
When integrating third-party APIs, malformed responses can cause silent failures in your application. Pasting the raw response into this validator before writing parsing logic helps you understand the exact structure and catch encoding issues early in the development cycle.
Frequently Asked Questions
It catches missing or extra commas, unquoted keys, single-quoted strings, trailing commas, mismatched brackets, invalid escape sequences, and duplicate keys at the same nesting level.
This tool validates JSON syntax (whether the document is well-formed). For JSON Schema validation (checking data against a schema definition), use the separate JSON Schema Validator tool.
Yes. Separate each document with a blank line, and the validator will check each one independently, showing results for every document.