Invalid JSON errors indicate malformed JSON data. Validating and checking JSON format can resolve it.

An 'Invalid JSON' error typically occurs when a Node.js application processes malformed JSON data, whether it’s parsing or responding to an API request. First, verify that the JSON input or response data conforms to JSON standards, with all keys and strings properly enclosed in double quotes. Functions like JSON.parse() throw errors if JSON is syntactically incorrect, so using tools like JSON.stringify() on complex objects can reveal any issues before parsing. In Express, middleware such as express.json() automatically parses JSON but may still fail on invalid payloads; configuring a custom error handler for JSON parsing can provide better error messaging. When working with external APIs, validate JSON responses, as APIs may occasionally return incomplete or malformed data. Ensuring data integrity, either through schema validation or robust error handling, can mitigate 'Invalid JSON' issues and improve API reliability.