Today I learned about JSONL format
Updated
•1 min read
Fun fact, while deep diving how Claude Code works, I realised some files were stored with a .jsonl format! What’s this, a typo?? 😀 Of course not….
It's a text format where each LINE is a valid JSON object. So why this and not just a JSON array?!
Regular JSON - one big array
[
{"id": 1, "name": "Alice"},
{"id": 2, "name": "Bob"}
]
JSONL - one object per line
{"id": 1, "name": "Alice"}
{"id": 2, "name": "Bob"}
Why?
- Logs and "file as database" -> just append!
- Reading with stream: we can parse each line, one by one, immediately! A slightly different array of objects!
And much more possibilities, I’m sure!
There are some things to take in consideration:
Not human-readable at a glance (no pretty formatting)
Can't have relationships between lines easily
Harder to edit manually
Less tooling support than regular JSON
I hope you enjoyed this nugget!! Happy coding!
