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Fuel for Fine-Tuning: What is JSONL?

JSONL, which stands for JSON Lines, is a file format that records JSON data line by line.

This format is particularly used for fine-tuning pre-trained AI models on the OpenAI platform.

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JSONL is not only useful for training AI but also for storing system logs and processing large volumes of data efficiently.


JSONL File Example​

In a JSONL file, each line contains a separate JSON object.

JSONL File Example
{"name": "John", "age": 30, "city": "New York"}
{"name": "Jane", "age": 25, "city": "Los Angeles"}
{"name": "Chloe", "age": 35, "city": "Paris"}

Why Use JSONL Instead of JSON for AI Training​

Several reasons justify using JSONL (JSON Lines) over traditional JSON for fine-tuning:

  1. Ease of line-by-line processing: Each line in a JSONL file represents a separate JSON object, making it simple to read and write data line by line, which is beneficial for handling large datasets.

  2. Memory efficiency: JSONL format minimizes memory usage because it allows processing data line by line without loading the entire file into memory at once.

  3. Log file similarity: JSONL's format is similar to log files, making it suitable for storing and processing logs or streaming data. You can record each event or data entry on an individual line.

  4. Parallel processing capability: JSONL files can be effectively processed using parallel computing resources such as threads or processes.

  5. Scalability: JSONL format allows for easy addition of new JSON objects at the end of the file, unlike single JSON object files which may require rewriting the whole file.


JSONL Characteristics​

  • Each line represents an independent piece of data, making it easy to understand.

  • Multiple JSON objects can be stored in a single file.

  • Typically uses the .jsonl or .ndjson file extension.

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