Validate JSON syntax

Check whether a text value is strict JSON and report its root type and size.

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ToolJSON Validator
Input
Output
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Preview

How it works

The text is parsed with JSON.parse; valid input reports its root type and serialized size, while parser errors expose the available message and location. No schema constraints are applied.

  • Any JSON root value is allowed.
  • Syntax checking remains separate from application validation.

Worked example

Valid JSON
A well-formed JSON object passes validation
Input
											{"name": "Alice", "age": 30, "active": true}
Output
												Valid: yes
Type: object
Size: 3

When to use this

API response checks, CI fixture gates, and configuration validation use strict syntax checks.

Edge cases

  • A top-level number or string is valid JSON even when an API expects an object.
  • Trailing commas are rejected by strict JSON syntax.
  • Comments cause an error rather than being stripped.

References