JSONL Explained: The Line-by-Line Format Powering AI Datasets

You're trying to load a 500,000-record dataset into your script. You reach for JSON — it's universal, readable, everyone knows it. But the moment you call JSON.parse() on a 2 GB file, your process runs out of memory and crashes. This is the problem JSONL (JSON Lines) was built to solve. And if you're working with AI training data, log pipelines, or any large-scale data processing, understanding JSONL will save you from real production pain. What Is JSONL? JSONL (also written .jsonl or called "JS