---
title: "JSON Validator - Free Online Tool | CanDoYa"
description: "Free online JSON validator to check syntax, locate errors and preview formatted JSON. No sign-up, no upload - your data stays in your browser."
url: https://candoya.com/tools/json-validator/
locale: en
type: browser-tool
---

# Free JSON Validator

Category: Developer

## What does a JSON validator do?

A JSON validator checks whether pasted text is legal JSON and shows the first syntax error with a line and column when the parser can locate it. Paste an API response, config file or webhook body to confirm it is valid, inspect a formatted preview and see basic structure stats without uploading anything.

This validator uses the browser's native JSON parser, so it follows the same strict rules your JavaScript code expects: double-quoted strings, quoted object keys, no comments and no trailing commas. Valid input is parsed locally and shown as a clean two-space preview.

## How to use it

1. **Paste your JSON** - Drop the object, array or JSON primitive into the input box.
2. **Read the status** - The validator updates live and reports whether the text is valid JSON.
3. **Fix any error** - If the parser can locate the problem, use the line and column in the message to jump to the first bad token.
4. **Copy the preview** - For valid JSON, copy the formatted preview or use the structure stats to sanity-check the payload.

## Who it's for

- **API debugging** when a response body looks right but your client refuses to parse it.
- **Config review** before saving package, app or infrastructure JSON files.
- **Webhook testing** when you need to verify a copied payload before sending it.
- **LLM output checks** when a prompt is supposed to return strict JSON for another tool.

## Expert note

JSON validation is stricter than JavaScript object syntax: single quotes, comments, unquoted keys, trailing commas, NaN and Infinity are all invalid JSON even though some JavaScript-like formats allow them.

## Frequently asked questions

### Is the JSON validator free?

Yes. The validator is free to use with no sign-up, no account and no usage limit. It runs in your browser and updates as you type.

### Is my JSON uploaded anywhere?

No. Your JSON is parsed locally in your browser. The text you paste into the validator is not sent to a server, which makes it suitable for private API responses, tokens, logs and config files.

### Why is my JSON invalid?

Common causes are trailing commas, single quotes, unquoted object keys, comments, missing brackets or a value such as NaN. The status message shows the parser's first error and includes a line and column when the browser exposes one.

### Does this validate JSON Schema?

No. This page validates JSON syntax only: whether the text can be parsed as JSON. JSON Schema validation checks whether a valid JSON document matches a separate schema, which is a different task.

### Can a JSON string, number or null be valid?

Yes. Modern JSON allows any serialized value at the top level, including an object, array, string, number, boolean or null. Some older APIs still expect the root to be an object or array, so check the receiving system's requirements.

### Why does the formatted preview change my spacing?

Whitespace outside JSON strings is insignificant. After validation, the preview parses the data and prints it with two-space indentation so you can read the structure without changing the actual values.

## Related tools

- [JSON Formatter](https://candoya.com/tools/json-formatter/)
- [JSON Minifier](https://candoya.com/tools/json-minifier/)
- [JSON to YAML Converter](https://candoya.com/tools/json-to-yaml/)
- [JSON to CSV Converter](https://candoya.com/tools/json-to-csv/)
- [Base64 Encode and Decode](https://candoya.com/tools/base64-encode-decode/)

---

*Markdown edition of <https://candoya.com/tools/json-validator/>, published for AI agents and other automated readers. Index of key pages: <https://candoya.com/llms.txt>.*