Skip to content
Convertto

JSON Validator — Find the Exact Syntax Error

Check whether JSON is valid, with the precise position of the error and what usually causes it.

A JSON validator tells you not just that a document is invalid but where. This converts the parser's character offset into a line and column, shows the offending line with a caret under it, and names the likely cause — trailing comma, single quotes, unquoted key or a comment, which cover almost every real JSON error.

Runs in your browser
Privacy
Runs entirely in your browser — nothing is uploaded
Cost
Free, unlimited, no sign-up

Frequently asked questions

Why is a trailing comma invalid when every editor allows it?

Because the JSON specification does not permit one, and it never has. Editors and TypeScript accept them because JSON5 and JSONC do — those are supersets, not JSON. Anything sent over the wire to a strict parser will be rejected.

My JSON has duplicate keys but still validates. Is that a problem?

It is valid but dangerous. JSON.parse keeps the last occurrence and drops the rest with no warning, while other languages differ — some keep the first, some error, some return both. If two systems read the same document they can legitimately disagree about its contents.

Can this validate against a JSON Schema?

No — this checks syntax. If you need to check a document against a schema, generate the schema first with the JSON Schema generator and validate with a library in your own toolchain, where the schema lives alongside the code that depends on it.

How to use the json validator

  1. 1Enter or paste your json.
  2. 2Choose the strictness.
  3. 3Turn "Show a structure summary" on or off as needed.
  4. 4Turn "Report duplicate keys" on or off as needed.
  5. 5The result appears immediately — copy or download it.

Embed this tool

Put the working json validator on your own site. It runs in your visitors' browsers exactly as it does here — free, no account, nothing uploaded.

Share this tool

Related tools

JSON Formatter & ValidatorFormat, validate, repair and analyse JSON — with errors that point at the exact line.Data Format ConverterConvert between JSON, YAML, XML, CSV, TSV and TOML in any direction, locally in your browser..env to JSON ConverterConvert .env files to JSON and back — for config migrations and CI variables.JSON DiffCompare two JSON documents and see exactly which keys were added, removed or changed.JSON FlattenerFlatten deeply nested JSON into dot-notation keys, or expand flat keys back into nested objects.JSON MergeDeep-merge several JSON documents, choosing how arrays and conflicts are resolved.

Last updated

More data & format tools