JSONL Converter
Convert between JSON arrays and JSONL format for LLM fine-tuning
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What is JSONL Format?
JSONL (JSON Lines) stores one JSON object per line instead of wrapping everything in an array. Each line is a valid, complete JSON object. This format is required by OpenAI and many other providers for fine-tuning datasets.
This converter transforms standard JSON arrays to JSONL format and vice versa — essential for preparing training data and processing streaming outputs.
Format Comparison
[{"a":1},{"a":2}]{"a":1}
{"a":2}Why Use JSONL?
Streaming
Process line-by-line without loading entire file into memory.
Append-Friendly
Add new records by appending lines. No need to rewrite the entire file.
FAQ
What APIs require JSONL?
OpenAI fine-tuning, Azure OpenAI, BigQuery exports, and many logging systems use JSONL.
Can JSONL have newlines in values?
Yes, but they must be escaped as \n within the JSON string. Each line = one complete JSON object.