JSON to NDJSON Converter
Convert JSON arrays and objects to Newline Delimited JSON (NDJSON) format for streaming, bulk operations, and big data processing. Each line contains exactly one valid JSON object. Perfect for log files, data pipelines, Elasticsearch bulk API, and Unix tooling.
Conversion Options
Recommended Settings
NDJSON Best Practices
- •Each line must contain exactly ONE valid JSON object - no embedded newlines
- •Always use UTF-8 encoding for consistent parsing across systems
- •Compact mode (minified lines) is standard for production use - saves bandwidth and storage
- •Pretty mode (formatted lines) is useful for debugging and human readability
- •NDJSON is append-friendly - add new objects by appending lines to the file
When to Use Compact vs Pretty Mode
- •Compact (default): Production use, APIs, log files, storage efficiency, streaming
- •Pretty mode: Debugging, development, human review, documentation examples
- •Compact reduces file size by ~30-50% compared to pretty-printed JSON
- •Use compact for machine consumption (APIs, databases, data pipelines)
- •Use pretty for developer tools (log viewers, debugging, API testing)
Pro Tips
- •Paste JSON and it auto-validates - conversion happens automatically when valid
- •NDJSON works seamlessly with Unix tools like grep, awk, sed for line-based processing
- •Perfect for streaming large datasets without loading everything into memory
- •All processing happens in your browser - your data never leaves your device
Most Popular
Most users keep compact mode ON and sort keys OFF for production NDJSON output
When to Use This Tool
Stream JSON data incrementally without loading entire datasets into memory. NDJSON allows processing one object at a time, making it perfect for APIs returning thousands or millions of records. Use for database exports, API pagination responses, and real-time data feeds. Parse and process each line independently for memory-efficient streaming.
Store application logs, server logs, and analytics events in NDJSON format. Each log entry is one line, making it easy to append new events, search with grep, filter with awk, and process with Unix tools. Perfect for centralized logging systems, error tracking, and audit trails. Enables fast line-based parsing without loading entire log files.
Perform bulk operations with databases and APIs that support NDJSON. Elasticsearch bulk API, MongoDB imports, and PostgreSQL COPY all use NDJSON format. Send thousands of create/update/delete operations in a single request. Each line represents one operation, allowing parallel processing and partial failure handling.
Process large datasets with Hadoop, Spark, and data processing frameworks that work with NDJSON. Each line can be processed independently, enabling distributed computing and parallel processing. Perfect for ETL workflows, data transformations, and machine learning training datasets. NDJSON splits cleanly across multiple workers for efficient parallel processing.
How It Works
Paste your JSON array or object into the input field on the left
The tool automatically validates JSON syntax to ensure proper formatting
For JSON arrays, each array element becomes one NDJSON line
For single JSON objects, the object becomes one NDJSON line
Compact mode (default) minifies each object to a single line without whitespace
Pretty mode formats each object with indentation for human readability
Sort keys option organizes object properties alphabetically for consistency
Strip empty objects option removes objects/arrays with no content
Conversion statistics show input/output sizes, line count, and size change
Arrays of primitives are rejected (NDJSON requires objects only)
Copy the NDJSON output to clipboard or download it as .ndjson file
All processing happens in your browser - your JSON data never leaves your device
100% Private
Files never leave your device. All processing happens locally in your browser.
Lightning Fast
Powered by Pure JavaScript for optimal performance on modern browsers.
Secure
No data collection, no tracking, no sign-up required.
Frequently Asked Questions
What is NDJSON and how is it different from JSON?
NDJSON (Newline Delimited JSON) is a format where each line contains exactly one valid JSON object, separated by newline characters. Unlike regular JSON, which can span multiple lines and contain nested arrays, NDJSON has one object per line. This makes it perfect for streaming, log files, and line-based processing with Unix tools. Each line can be parsed independently.
When should I use NDJSON instead of regular JSON?
Use NDJSON when you need to stream large datasets, process data incrementally, or work with log files. It's ideal for APIs returning thousands of records, bulk database operations (Elasticsearch, MongoDB), data pipelines, and Unix tool processing (grep, awk). Use regular JSON for configuration files, small API responses, and when you need complex nested structures preserved.
Can I convert a single JSON object to NDJSON?
Yes! A single JSON object becomes one NDJSON line. While NDJSON is commonly used with arrays of objects, single objects are valid NDJSON. This is useful when you want to append individual records to an existing NDJSON file or send single events to a streaming API. The tool handles both single objects and arrays.
What's the difference between compact and pretty mode?
Compact mode (default) minifies each JSON object to a single line with no whitespace - this is standard NDJSON format used in production. Pretty mode formats each object with indentation across multiple lines within each NDJSON entry - useful for debugging and human review. Compact mode reduces file size by 30-50% and is recommended for APIs, databases, and log files.
Does NDJSON work with nested objects?
Yes, NDJSON supports nested objects within each line. Each NDJSON line can contain a complex JSON object with nested structures, arrays, and deep hierarchies. The restriction is that the entire object must fit on one line (when compacted). Nested objects are preserved exactly as they appear in the original JSON - only the outer array structure is converted to newline-separated format.
How do I validate NDJSON format?
Valid NDJSON must have one JSON object per line, separated by newline characters (\n). Each line must be independently parseable as valid JSON. No embedded newlines are allowed within objects (use compact mode). Arrays of primitives are not valid NDJSON - only arrays of objects. This tool automatically validates your input and ensures the output follows NDJSON specifications.
Why does the tool reject arrays of primitives?
NDJSON format requires each line to be a JSON object, not a primitive value. Arrays like [1, 2, 3] or ['a', 'b', 'c'] are not valid NDJSON input because primitives can't be spread across lines meaningfully. If you need to convert primitive arrays, wrap each value in an object first: [{value: 1}, {value: 2}, {value: 3}].
Is my JSON data secure using this tool?
Your data is completely private. All conversion happens entirely in your browser using JavaScript - nothing is sent to any server. The tool works offline after initial load. Your JSON never leaves your device. However, remember that NDJSON output still contains your data in plaintext - review it before sharing or storing in public locations.