Import JSON Lines (JSONL / NDJSON / LDJSON) to PostgreSQL

by

Posted on by

Want to import data from JSON Lines (JSONL / NDJSON / LDJSON) file to PostgreSQL ?

Try Withdata FileToDB, a desktop JSONL to PostgreSQL converter for Windows, MacOS, and Linux, Import JSON Lines to PostgreSQL, Easy and Fast.

  • Can run in GUI mode, Step by Step, just a few mouse clicks.
  • Can run in Command line, for Scheduled Tasks and Streams.
  • Convert locally and privately, avoid uploading large or private JSONL file(s) to online services.

Download Withdata FileToDB Download FileToDB

JSON Lines text format (JSONL), also called Newline-delimited JSON (NDJSON), or Line-delimited JSON (LDJSON). JSON Lines files may be saved with the file extension .jsonl, *.ndjson, *.ldjson.

Import data from JSON Lines (JSONL / NDJSON / LDJSON) file to PostgreSQL

Login to PostgreSQL -> Choose JSON Lines file -> Set PostgreSQL table -> Import JSON Lines to PostgreSQL

Choose PostgreSQL and logon.

load JSON Lines data to PostgreSQL table - Choose PostgreSQL and logon

Click “Wizard – 1 File To 1 Table” at task dialog.

import JSON Lines data to PostgreSQL table - task window

Select the “JSON” file type.

Import JSON Lines file data to PostgreSQL table - select file type

then show the wizard.

1. Open a JSON Lines (JSONL / NDJSON / LDJSON) file.

Support large ( > 4GB ) JSON Lines file.

Import Data From JSON Lines File To PostgreSQL - open JSON Lines file

Here is the file’s content.

Import Data From JSON Lines File To PostgreSQL - source JSON Lines file

FileToDB will parse JSON Lines file.

2. Select a PostgreSQL table and config fields.

Load Data From JSON Lines File To PostgreSQL - select table

3. Preview data will be in PostgreSQL table.

Transfer Data From JSON Lines File To PostgreSQL - preview

4. Import JSON Lines data to PostgreSQL.

Import Data From JSON Lines File To PostgreSQL - import data

View imported data in PostgreSQL table

Convert JSON Lines to PostgreSQL - view data

Convert JSON Lines (JSONL / NDJSON / LDJSON) to PostgreSQL in command line

Save “JSON Lines to PostgreSQL” session, then you can:

Set scheduled tasks for converting JSON Lines (JSONL / NDJSON / LDJSON) to PostgreSQL

You can schedule and automate this “JSON Lines to PostgreSQL” conversion task by:

  1. Save session and create .bat (Windows) or .sh (Linux/macOS) file for “JSON Lines to PostgreSQL” conversion.
  2. Set scheduled task for “JSON Lines to PostgreSQL” conversion.

FAQ

More tools for JSONL / NDJSON / LDJSON.

JSON Lines → PostgreSQL reference

Type mapping

Value kindin JSON Linesin PostgreSQL
Int1234 (number)integer
Bigint9007199254740993bigint
Decimal1234.56 (number)numeric(p,s)
Float1.234e10 (number)double precision
Text"text" (string)varchar(n)
Long text"multi-line\ntext"text
Date"2026-09-18" (string)date
Datetime"2026-09-18T14:30:00Z" (string)timestamp
Binary"base64:..." (string)bytea
Booleantrue / false (boolean)boolean
JSONnested object on the same linejsonb

Dialect differences

JSON Lines is a file format and PostgreSQL is a database server, so the target has to be told the types the file never carried - the rows below are where the two sides diverge.

Propertyin JSON Linesin PostgreSQL
port—5432
identifiersDouble quotes; backslash escapes (a newline inside a string..."double quotes"
row limit—LIMIT n
datesNo date type: dates arrive as stringstimestamp, timestamptz, date, time
long text—TEXT
binaryNot supported natively - base64 inside a stringBYTEA
separatorNewline between records—
encodingUTF-8 by definition—
typingSame as JSON, but records cannot nest across lines—
shapeFlat streamTables of rows and columns
ceilingStreams, so it scales past what a single JSON document can ...—

Command line

SideCommand
PostgreSQLpg_dump or COPY ... TO
PostgreSQL (load)COPY ... FROM

JSON to PostgreSQL without the manual work

For batch jobs, large files and scheduling use the JSON to PostgreSQL converter — an offline desktop app for Windows, Linux and macOS. Free trial.