JSON to NDJSON Converter

JSON ↔ NDJSON Converter

The JSON ↔ NDJSON Converter transforms standard JSON arrays into newline-delimited JSON (NDJSON) and converts NDJSON back into a JSON array. NDJSON is a streaming-friendly format where each line is a valid JSON object. It is widely used in logging systems, data pipelines, search indexing, and big data tools because it is easy to parse line-by-line.

If you work with large datasets, NDJSON lets you process records without loading everything into memory. This is great for streaming, ETL jobs, and API responses that return large lists. This tool lets you quickly switch between formats, validate your data, and export it for downstream tools.

What NDJSON is and why it matters

• Each line is a valid JSON object.
• Newline characters separate records.
• Ideal for streaming, logging, and incremental processing.
• Works well with tools like Elasticsearch, Logstash, and CLI pipelines.

How to use the converter

1. Paste a JSON array or NDJSON on the left.
2. Select the conversion direction: JSON → NDJSON or NDJSON → JSON.
3. Copy or download the output from the right.

Example: JSON to NDJSON

Input JSON array:

[
  { "id": 1, "name": "Avi" },
  { "id": 2, "name": "Riya" }
]

NDJSON output:

{"id":1,"name":"Avi"}
{"id":2,"name":"Riya"}

Example: NDJSON to JSON

Input NDJSON:

{"event":"login","user":"avi"}
{"event":"logout","user":"avi"}

JSON array output:

[
  { "event": "login", "user": "avi" },
  { "event": "logout", "user": "avi" }
]

Common errors and fixes

• Invalid JSON line: Each NDJSON line must be valid JSON. Fix syntax errors or remove empty lines.
• Extra commas: NDJSON does not use commas between objects. Remove commas or use JSON array format instead.
• Trailing spaces: Whitespace is allowed, but stray characters after a JSON object can break parsing.
• Non-object lines: NDJSON expects a JSON object per line. If a line is a string or number, wrap it in an object.
• Large files: Very large NDJSON can be slow in the browser. Split files or process in chunks.

Best practices for NDJSON

• Use one JSON object per line for consistency.
• Avoid blank lines in NDJSON files.
• Validate a sample of lines with JSON Validator before bulk processing.
• Use JSON Formatter after converting back to JSON arrays for readability.
• Keep keys consistent across records for easier downstream processing.

NDJSON for streaming and bulk APIs

NDJSON shines in streaming contexts because parsers can process one line at a time. This means you can handle large datasets without loading everything into memory. Many bulk APIs expect NDJSON for this reason. For example, Elasticsearch uses NDJSON in its bulk indexing endpoints, and many log ingestion systems accept NDJSON directly.

If you are sending NDJSON over the network, ensure that each line ends with a newline character. Some systems require a trailing newline at the end of the file for the last record to be processed.

Schema consistency in NDJSON

While NDJSON does not enforce a schema, consistent keys across lines are important for analytics and indexing. If each line contains a different set of keys, downstream systems may generate sparse schemas or inconsistent columns. Consider normalizing keys or using a schema validator on sample lines before ingesting large files.

Common pipeline patterns

• Logs → NDJSON: Convert JSON arrays to NDJSON for line-by-line log ingestion.
• NDJSON → CSV: Convert to JSON arrays, flatten, then export to CSV.
• NDJSON → SQL: Convert to JSON arrays, flatten, then generate SQL inserts.

Checklist for clean NDJSON

1. Ensure each line is valid JSON.
2. Remove blank lines or stray characters.
3. Keep key sets consistent across records.
4. Validate samples before full ingestion.

NDJSON vs CSV

NDJSON preserves nested structures and data types, while CSV is flat and text-based. If your data contains nested objects or arrays, NDJSON is usually safer. If you need spreadsheets or relational imports, convert NDJSON to a JSON array, flatten it, then export to CSV.

For analytical workflows, NDJSON is often a better staging format because it keeps the original shape, allowing you to transform data later without losing context.

Troubleshooting tips

• If parsing fails, validate a single line to locate the error.
• Remove BOM markers or invisible characters at the start of files.
• Ensure the file is UTF-8 encoded for maximum compatibility.
• Check for lines that contain only commas or brackets from a JSON array.

Use cases

Log processing: Many logging tools expect NDJSON because it streams easily.

Search indexing: Elasticsearch bulk APIs often accept NDJSON.

Data pipelines: NDJSON works well with streaming tools and line-based processing.

Batch exports: Convert a JSON array to NDJSON for incremental processing.

FAQs

What is the difference between JSON and NDJSON?
JSON is often a single object or array. NDJSON is many JSON objects separated by newlines.

Can NDJSON contain arrays?
Each line must be valid JSON, so arrays are allowed, but objects are recommended for consistency.

Is NDJSON the same as JSON Lines?
Yes. NDJSON is also called JSON Lines or JSONL.

How do I validate NDJSON?
Validate each line individually. This tool does that during conversion.

Is my data uploaded?
No. Everything runs locally in your browser.

Can I convert NDJSON to CSV?
Yes. Convert to a JSON array, flatten if needed, then use JSON to CSV.

What if I get empty output?
Check for invalid JSON lines or ensure you selected the correct direction.

Does this support large files?
It can handle moderate sizes in the browser. For very large files, process in chunks.

Can NDJSON include nested objects?
Yes. Each line can contain nested objects and arrays as long as it is valid JSON.

Why is my bulk API rejecting NDJSON?
Check for missing newlines, invalid JSON lines, or unexpected fields.

How do I debug NDJSON errors?
Validate lines individually and inspect the first failing line.

Can I use NDJSON for backups?
Yes. NDJSON is convenient for backups because each record is independent and easy to restore.

Does NDJSON require a trailing newline?
Some systems expect it, so adding a trailing newline is a safe default.

Can I compress NDJSON files?
Yes. NDJSON compresses well with gzip and is commonly stored compressed in pipelines.

Keyword‑targeted phrases

• json to ndjson
• ndjson to json
• json lines converter
• jsonl converter
• ndjson online