NDJSON / JSONL Validator
Drop any .ndjson or .jsonl file to instantly check its structure. Validates JSON syntax on every line, checks for consistent keys across objects, flags encoding issues, empty lines, duplicate keys, and previews the first few records. Nothing leaves your browser.
NDJSON / JSONL File
Drop a .ndjson or .jsonl file here, or
Supports .ndjson, .jsonl, and .json files up to 50 MB
⛔
Wrong file type — only .ndjson, .jsonl, or .json files are supported. You dropped a file.
Validation Errors
Warnings
✓ Valid NDJSON
Top-level Keys
Data Preview (first 5 records)
How It Works
1
Drop your NDJSON fileDrag it onto the drop zone or click "browse" to select it from your device. Supports .ndjson and .jsonl files.
2
Line-by-line analysisEvery non-empty line is parsed as JSON. Syntax errors are reported with the exact line number. Key consistency, duplicate keys, and value type uniformity are checked across all records.
3
Review the reportGet a pass/fail result plus full stats: record count, unique top-level keys, empty lines, file size, line endings, and a live data preview of the first 5 records.
What Gets Validated
- JSON syntax per line — every non-empty line is parsed with
JSON.parse(). Syntax errors are reported with their exact line number and the parser's error message. - Root value type — checks that each line parses to a JSON object
{}or array[], not a bare string, number, ornull. - Key consistency — collects all top-level keys from every record and flags keys that appear in some records but not others, which often indicates missing fields.
- Duplicate keys — detects repeated keys within a single JSON object, which causes silent data loss in most parsers.
- Empty lines — counts and flags blank lines; trailing empty lines are tolerated but interior ones are warned about.
- Encoding issues — detects a UTF-8 BOM (byte order mark) and null bytes that indicate binary content or wrong encoding.
- File statistics — reports total records, unique key count, empty lines, file size, and line ending style (CRLF vs LF).
- Data preview — renders the first 5 records in a formatted table so you can visually confirm the parse is correct.
🔒 Privacy & Security
All validation is performed locally using the Web File API and the FileReader API. Your NDJSON data is never sent to a server. Suitable for sensitive business data, API logs, event streams, or any private JSON records.