JSONL / NDJSON Validator
Validate JSON Lines files line-by-line. Each line must be a valid JSON object.
Click Validate to check your JSONL file
What Is a JSONL Validator?
A JSONL validator checks a newline-delimited JSON file (JSON Lines or NDJSON) to ensure every line is a valid, standalone JSON value — typically a JSON object or array.
JSONL is used for log files, event streams, and machine learning training data where each record is one JSON value per line. Validating before processing catches malformed lines that would break downstream parsers.
Common Use Cases
- check_circleValidate a JSONL log file before importing into a log analysis tool
- check_circleCheck an NDJSON event stream for malformed lines
- check_circleValidate a JSON Lines machine learning dataset before training
- check_circleVerify JSONL output from a data pipeline before downstream processing
- check_circleCheck each line of a JSONL file exported from a database
- check_circleValidate a JSONL file before loading into BigQuery or Elasticsearch
Line-by-Line Validation
Validates each line independently as a complete JSON value and reports the line number of any error.
Error Line Reporting
Shows the exact line number and parse error for every invalid JSON line in the file.
Large File Support
Handles JSONL files with thousands of lines efficiently.
Frequently Asked Questions
What is JSONL / JSON Lines?
JSONL (JSON Lines) is a text format where each line is a complete, valid JSON value. It is used for logs, event streams, and ML datasets where records are processed one at a time.
How is JSONL different from a JSON array?
A JSON array is a single value containing all records. JSONL has one record per line with no surrounding array brackets. JSONL is better for streaming since you can process one line at a time without loading the full file.
Does the validator allow empty lines?
Empty and whitespace-only lines are skipped and do not cause validation errors, matching the JSONL specification.
What does valid JSONL look like?
Each line must be a complete JSON value — most commonly an object like {"key": "value"}. Partial JSON, multi-line JSON objects, or bare strings without quotes are invalid.
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