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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BigQuery ready
OpenAI fine-tuning
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Always free
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.
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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.