Input
1
Ln 1 Col 1
Indent
Output
// output appears here
—

Jsonic's JSON Validator checks your JSON for syntax errors and tells you exactly where they are. Paste your JSON and click Format — if it's valid, you get pretty-printed output; if not, you get a specific error message with line and column numbers. Common errors detected include trailing commas, single-quoted strings, unquoted keys, missing brackets, and stray characters. All validation runs in your browser — your data is never uploaded.

How to validate JSON online

  1. Paste your JSON into the left panel.
  2. Click Format — the validator parses the JSON immediately.
  3. If valid, you see pretty-printed JSON in the output panel.
  4. If invalid, an error banner shows the exact line and column of the first error.
  5. Fix the error and click Format again to confirm.

FAQ

What errors does the JSON validator catch?

The validator catches all JSON syntax errors: trailing commas in objects and arrays, single-quoted strings (JSON requires double quotes), unquoted keys, missing or extra brackets and braces, duplicate keys, invalid escape sequences, and numbers with leading zeros.

Why is my JSON invalid?

The most common causes are: (1) trailing commas after the last item in an array or object, (2) single quotes instead of double quotes around strings or keys, (3) JavaScript-style comments (// or /* */), which are not valid in JSON, (4) undefined or NaN values, which are not JSON primitives.

What is the difference between JSON syntax validation and JSON Schema validation?

Syntax validation checks that the JSON is well-formed — correct brackets, quotes, and types. Schema validation checks that the data matches an expected structure — required fields, types, and value constraints. Use this tool for syntax; use the JSON Schema Validator for structure.

Can I validate a JSON file?

Yes. Use the upload button to load a JSON file from disk. The validator reads it and checks for errors immediately.

Is there a size limit for validation?

No hard limit — it depends on browser memory. Large JSON files (several MB) validate instantly on modern devices.

Is my JSON data uploaded anywhere?

No. Validation runs entirely in your browser using the built-in JSON.parse algorithm. Nothing is sent to a server.