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 data, log pipelines, or any large-scale data processing, understanding JSONL will save you from real production pain. There's no wrapping array, no commas between records - just one JSON object per line, separated by newlines.