JSON Validator
Check JSON syntax and structure for errors.
Valid. Root type: object Top level: 2 keys Bytes: 152
What is a JSON Validator?
A JSON validator parses a document against the JSON grammar and reports the first place the grammar is violated. Unlike a schema validator it says nothing about whether the right fields are present — it answers the narrower and more urgent question of whether the text is JSON at all.
When the document is valid, the tool also reports its shape: the root type, how many keys or items sit at the top level, and its size in bytes. That is usually enough to confirm you pasted the payload you meant to.
When you need it
- A request is being rejected with a parse error and you need to know if the body is at fault.
- A hand-edited configuration file stopped loading after a merge.
- A JSON column in a database is failing to insert.
- A CI step fails on a generated manifest and the error message gives no position.
- You want to confirm a file is JSON and not JSON Lines, JSON5 or a truncated download.
How to use the JSON Validator
- Paste the document into the input panel — validation runs immediately, with no button to press.
- If it is valid, read the summary: root type, top-level size and byte count.
- If it is not, read the parser message and the line and column where parsing stopped.
- Fix the reported position, and the result updates as you type.
Examples
JSON Validator features
Frequently asked questions
Does this validate against a JSON Schema?
No. This tool checks syntax only — whether the text is well-formed JSON. Checking that the right fields are present with the right types is a separate job, done with a JSON Schema validator.
Is JSON with comments valid?
No. Comments are not part of JSON. Formats that allow them — JSON5, JSONC, and many config dialects — are supersets, and a strict parser rejects them.
Are duplicate keys an error?
The specification leaves it undefined, and most parsers accept the document and keep the last value. It is valid syntax but a genuine source of bugs, so it is worth removing.
What about JSON Lines?
A .jsonl file is one JSON document per line, so the file as a whole is not valid JSON. Validate a single line at a time.
Is my data uploaded to a server?
No. Every iZZi DevTools tool runs inside your browser using the standard web platform. The data you paste is processed on your own machine and is never transmitted, stored or logged by us.
Do I need an account?
No. Every core tool is free, unlimited and works without signing in. An account only adds conveniences such as saved snippets and history.
Does it work offline?
Once the page has loaded, yes. Because the processing happens in the browser rather than on a server, the tool keeps working if your connection drops.