JSON: Validate¶
Checks whether a given text is valid JSON. Returns a boolean indicating validity and an accompanying error message if invalid. Does not modify or parse the input beyond validation.
Usage¶
Use this node when you need to verify that a string is valid JSON before parsing it or passing it into downstream steps that expect structured data. Typical workflow: receive or construct a JSON string, validate with this node, then conditionally branch—parse or proceed if valid, or log/handle the error if invalid.
Inputs¶
| Field | Required | Type | Description | Example |
|---|---|---|---|---|
| json_string | True | STRING | The text to validate as JSON. Supports multiline strings. The node checks only JSON syntax validity. | {"name": "Salt", "count": 3} |
Outputs¶
| Field | Type | Description | Example |
|---|---|---|---|
| is_valid | BOOLEAN | True if the input is syntactically valid JSON; otherwise False. | True |
| error_message | STRING | Error message describing why validation failed. Empty string when is_valid is True. | Expecting property name enclosed in double quotes: line 1 column 2 (char 1) |
Important Notes¶
- Validation scope: This node validates JSON syntax only; it does not validate against a schema or enforce specific fields.
- Empty success message: When the JSON is valid, the error_message output is an empty string.
- Input type: The input must be a STRING; other types should be converted to string JSON first.
- Multiline support: Multiline JSON strings are accepted.
- Common pitfalls: Single quotes, trailing commas, and unescaped characters will cause validation to fail.
Troubleshooting¶
- Always invalid with 'Expecting value': Ensure the input isn't empty or whitespace-only and that it starts with a valid JSON token (e.g., {, [, ")
- Using single quotes: Replace single quotes with double quotes for keys and string values to conform to JSON.
- Trailing commas: Remove any trailing commas in objects or arrays.
- Encoding issues: If you see an 'Unexpected error', ensure the string is properly encoded (e.g., UTF-8) and characters are correctly escaped.
- Valid but downstream fails: Being valid JSON doesn't guarantee the structure matches what downstream steps expect (e.g., object vs array). Inspect the parsed structure.