Online JSON Validator & Syntax Checker

Identify syntax errors, invalid tokens, trailing commas, and unquoted keys with line and column precision.

100% Client-Side Processing — your JSON never leaves this browser. Works offline. How it works

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About this tool

How the JSON Validator works

Validate JSON syntax with pinpoint line and column error reporting. 100% private in-browser validation with one-click repair for syntax issues.

Line & Column Pinpoint

Highlights the exact character and line where the syntax error occurs with a visual cursor pointer.

Detailed Diagnostics

Detects trailing commas, single quotes, unquoted keys, duplicate keys, and unescaped characters.

One-Click Repair

Quickly transfer invalid JSON to our built-in JSON Repair tool to fix errors automatically.

RFC 8259 Compliant

Strict conformance with the official JSON specification to ensure backend compatibility.

FAQ

Common questions

Why is my JSON invalid?

Common causes include trailing commas after the last item in an object or array, using single quotes instead of double quotes, forgetting quotes around object keys, or unescaped control characters.

Does this validator detect duplicate keys?

Yes, SnipFerry warns when duplicate keys exist within the same object, which can cause subtle data-overwriting bugs in backend parsers.

Can this tool fix my invalid JSON?

Yes! When an error is detected, click "Fix with JSON Repair" to automatically repair trailing commas, quotes, and Python literals.

Does the validator work offline?

Yes. Once loaded, all validation runs 100% client-side without any internet connection needed.

Keep going

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