ToolPortaToolPortaFree online utilities
Developer Documentation
Python
Updated September 19, 2026

Validate JSON in Python

Validate JSON syntax and handle parser errors without mutating the input in Python.

Syntax validation answers one question: can the input be parsed as JSON? It is different from JSON Schema validation, which checks the shape and constraints of already valid JSON data.

Quick Start#

The following example uses the standard Python API or a widely used package for this task.

Syntax validation#

Python
1import json23def validate_json(source: str) -> tuple[bool, str | None]:4    try:5        json.loads(source)6        return True, None7    except json.JSONDecodeError as exc:8        return False, f"{exc.msg} at line {exc.lineno}, column {exc.colno}"910print(validate_json('{"ok": true}'))

Common Operations#

This second pattern covers a common production operation or a safer way to handle real input.

JSON Schema#

Python
1# pip install jsonschema2from jsonschema import validate34schema = {5    "type": "object",6    "required": ["name"],7    "properties": {"name": {"type": "string"}},8}910validate(instance=json.loads(source), schema=schema)

Important Notes#

json.loads validates syntax only. Use a JSON Schema library or application-level checks when structure and field constraints matter.

Best Practices#

  1. Treat external input as untrusted and handle parse/validation errors explicitly.
  2. Keep encoding, units, formats, and library-specific mapping rules explicit at system boundaries.
  3. Add test vectors that cover empty input, Unicode text, malformed input, and representative production data.

References#

Implement JSON Validator in other languages:

C#C#GOGoJAVAJavaJSJavaScriptTSTypeScript