JSONL guides

Practical references for the format and the tools around it.

• What is JSONL?The format, its rules, and when to use it.
• JSONL vs JSONHow they differ and how to choose.
• JSONL vs NDJSONWhether the two names mean different things.
• How to fix common JSONL errorsWhat each error means and how to fix it.
• How to open large JSONL filesOptions for multi-GB files, in the browser and on the command line.
• OpenAI Batch API JSONL formatInput, output and error files, with limits.
• Anthropic Message Batches results formatResult types, custom_id rules and limits.
• Where Claude Code stores session logsLocation, structure and how to read them.
• Browser JSONL benchmarkMeasured indexing and search speed on a 5 GiB file.