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NDJSON

NDJSON (newline-delimited JSON) puts one independent JSON object per line, suiting streaming processing of large datasets.

Purpose

To provide a JSON format that can be processed as a stream without loading a whole array into memory.

Mechanism

Each line is a complete JSON value separated by newlines, with no outer array wrapper. A parser reads line by line, enabling streaming. It is common for logs, database exports, and API streams.

Use cases

  • Elasticsearch bulk API
  • Database export and import
  • Log stream processing
  • An intermediate format for big data pipelines

Examples

  • Input 
    {"a":1}
{"a":2}
    Output 
    Two JSON objects, one per line

    Newline-delimited

Common errors

A string containing a literal newline breaks the line format
Newlines inside JSON strings are already escaped as \n

Related terms

JSON
JSON (JavaScript Object Notation) is a lightweight data interchange format based on JavaScript object literals, using key-value pairs and arrays.
GLOSSARY
JSONL
JSONL (JSON Lines) is equivalent to NDJSON: one JSON object per line, an alternative name for the same format.
GLOSSARY
CSV
CSV (comma-separated values) is a tabular data format that separates fields with commas; RFC 4180 defines the standard, and it is widely used for data import and export.
GLOSSARY

Related tools

Ndjson Format
Ndjson Format — pure client-side tool. Privacy-first, no server round-trip.
TOOL
Ndjson Validate
Ndjson Validate — pure client-side tool. Privacy-first, no server round-trip.
TOOL

References