Free CSV to JSONL — BigQuery · OpenAI · Elasticsearch — no upload

Convert CSV to JSONL
One JSON object
per line.

Free CSV to JSON Lines (JSONL / NDJSON) converter. One JSON object per line — the standard format for BigQuery streaming inserts, MongoDB mongoimport, Elasticsearch bulk API, OpenAI fine-tuning and Hugging Face datasets. Upload or paste. No server.

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Need the reverse? JSONL to CSV converter
CSV to JSONL Converter  100% client-side
Drop your CSV file here
.csv, .txt or .tsv — or paste below
or paste CSV directly
 JSONL ready 

      

    

  

 
  
Where JSONL is the required format

  
Six major platforms that use JSON Lines as their standard import format.

  

    
BigQuery
bq load --source_format=NEWLINE_DELIMITED_JSON — streaming inserts and batch loads both use JSONL.

    
OpenAI fine-tuning
Training data for GPT fine-tuning must be in JSONL format: one {"messages": [...]} object per line.

    
Elasticsearch
Bulk API requires alternating action/source JSONL pairs: {"index":{}} then {"field":"value"}.

    
MongoDB mongoimport
mongoimport --type json reads NDJSON by default — one document per line, no --jsonArray flag needed.

    
Hugging Face Datasets
load_dataset("json", data_files="data.jsonl") — JSONL is the standard format for HF dataset uploads.

    
DuckDB
SELECT * FROM read_ndjson_auto('data.jsonl') — DuckDB reads JSONL natively with schema inference.

  

 
  
CSV to JSONL code examples

  

    
Python — simplest

    
import csv, json
 
with open('data.csv') as f_in, open('output.jsonl', 'w') as f_out:
    for row in csv.DictReader(f_in):
        f_out.write(json.dumps(row) + '\n')

    
All values are strings — add type coercion before json.dumps() for numeric fields.

  

  

    
BigQuery import

    
bq load \
  --source_format=NEWLINE_DELIMITED_JSON \
  --autodetect \
  myproject:mydataset.mytable \
  gs://bucket/data.jsonl

    
--autodetect infers the BigQuery schema from the first 100 lines of JSONL. Upload the .jsonl from CSVShift to GCS first.

  

 
  

 
  
Related CSV tools

  
JSONL to CSV
Convert JSON Lines / NDJSON files into a CSV spreadsheet.
CSV to TSV
Comma-separated to tab-delimited, with quotes handled.
CSV to JSON
Arrays, objects or keyed JSON from any CSV, with types.
JSON to CSV
Flatten nested JSON into a clean CSV table.
CSV to XML
XML with your own root and row tags from any CSV.
XML to CSV
Flatten nested XML elements and attributes into CSV.
CSV to YAML
Valid YAML with correct quoting from any CSV.
YAML to CSV
Flatten YAML sequences and mappings into a CSV table.
CSV to MongoDB
NDJSON, JSON array or insertMany() for MongoDB from a CSV.
All data format converters 

 
  
 
  

    
Frequently asked questions

    
What is JSONL / NDJSON?
JSONL (JSON Lines) and NDJSON (Newline Delimited JSON) are the same format — one JSON object per line, separated by newlines. Unlike a JSON array, JSONL can be streamed and processed line-by-line without loading the entire file into memory. It is the standard format for BigQuery, MongoDB, Elasticsearch and OpenAI fine-tuning datasets.

    
How do I convert CSV to JSONL in Python?
import csv, json; [open('out.jsonl','w').write(json.dumps(r)+'\n') for r in csv.DictReader(open('f.csv'))]. For type coercion, convert string values to int/float/bool before json.dumps().

    
Is my data safe when converting CSV to JSONL online?
Yes. CSVShift converts your CSV entirely in your browser. No data is uploaded to any server.