jsonl

JSONL, also known as JSON Lines or newline-delimited JSON, is a text-based data interchange format in which every line of a file is a valid JSON value. Typically each line contains a single JSON object, but any JSON value is allowed. Lines are separated by newline characters, and the file is usually encoded in UTF-8. Because records are independent, a JSONL file can be appended to or processed line by line without loading the entire file into memory.

JSONL is designed for streaming and incremental processing. It supports large datasets and log-style data because parsers can process one line at a time. This makes it suitable for data ingestion pipelines, log aggregation, and machine learning datasets where records arrive over time or are too large to fit in memory. Compared with a conventional JSON document that contains a single array of objects, JSONL allows efficient appends and parallel processing and works well with line-oriented tooling.

However, JSONL is not a single valid JSON document. Some software expects a JSON array or a top-level object, so additional wrapping may be required for compatibility. Human readability is lower than nicely formatted JSON, though each line remains individually parseable. If a line becomes corrupted, only that line fails to parse, leaving the rest of the file usable.

Example lines:

{"id":1,"name":"Alice","active":true}

{"id":2,"name":"Bob","active":false}

Many programming languages offer libraries for line-delimited JSON parsing (or simple line-by-line parsing of JSON values). It is widely supported in data processing frameworks and logging pipelines as a lightweight, streaming-friendly format.