JSONL.rest
The definitive resource for JSON Lines format - Your go-to reference for streaming data, AI training, and efficient log processing
Our Mission
JSONL.rest is the Wikipedia of JSON Lines format - a comprehensive, developer-focused resource that serves as the single source of truth for everything JSONL. Whether you're processing streaming data, training AI models, or managing massive log files, we provide the knowledge and tools you need.
This site isn't just a collection of documentation; it's a living project built from real-world experience. The team at RJL.dev - a group of practicing software engineers and architects - created and actively maintains every piece of content you'll find here. We've navigated the challenges, debugged the tricky edge cases, and optimized the patterns so you can learn from our expertise.
Built by developers, for developers. We believe in making data formats accessible, understandable, and easy to implement. From beginners to experts, JSONL.rest is your trusted companion in the world of newline-delimited JSON.
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Reference Pages
Glossary Terms Defined
Parser Errors Decoded
Common Mistakes Explained
Languages With Code Examples
Server Round Trips To Validate
What is JSONL?
Definition
JSON Lines (JSONL), also known as Newline Delimited JSON (NDJSON), is a convenient format for storing structured data that may be processed one record at a time. Each line is a valid JSON value, separated by newline characters.
Core Benefits
- Built for Streaming: Process one line at a time - ideal for data streams or massive files
- Low Memory Footprint: Handle terabyte files on machines with minimal RAM
- Easily Appendable: Add new data by appending a line - no parsing or rewriting required
- Robust: One corrupted line won't break the entire file
Quick Example
JSON (Traditional)
[
{"name": "Alice", "age": 30},
{"name": "Bob", "age": 25},
{"name": "Charlie", "age": 35}
]JSONL (Lines)
{"name": "Alice", "age": 30}
{"name": "Bob", "age": 25}
{"name": "Charlie", "age": 35}Notice: Each line is an independent JSON object - perfect for streaming and processing!
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