A standard for delimiting JSON in stream protocols.

1. Introduction

1.1 About

There is currently no standard for transporting instances of JSON text within a stream protocol, apart from [Websockets], which is unnecessarily complex for non-browser applications.

A common use case for NDJSON is delivering multiple instances of JSON text through streaming protocols like TCP or UNIX Pipes. It can also be used to store semi-structured data.

1.2 Terminology

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119. [RFC2119]

2. Example NDJSON


(with \n line separators)

3. Functional Specification

3.1 Serialization

Each JSON text MUST conform to the [RFC7159] standard and MUST be written to the stream followed by the newline character \n (0x0A). The newline charater MAY be preceeded by a carriage return \r (0x0D). The JSON texts MUST NOT contain newlines or carriage returns.

All serialized data MUST use the UTF8 encoding.

3.2 Parsing

The parser MUST accept newline as line delimiter \n (0x0A) as well as carriage return and newline \r\n (0x0D0A).

If the JSON text is not parseable, the parser SHOULD raise an error. The parser MAY silently ignore empty lines, e.g. \n\n. This behavior MUST be documented and SHOULD be configurable by the user of the parser.

3.3 MediaType and File Extensions

The MediaType [RFC4288] for Newline Delimited JSON SHOULD be application/x-ndjson.

When saved to a file, the file extension SHOULD be .ndjson.

This specification is copyrighted by the authors named in section 4.1. It is free to use for any purposes commercial or non-commercial.

4.1 Authors

The following authors are responsible for the NDJSON core-specification:

Thorsten Hoeger
Taimos GmbH
Hohenzollernstrasse 32
D-73262 Reichenbach
Chris Dew
Finn Pauls
Jim Wilson

4.2 Contact

This specification and any related work is located at Discussion and help is located at

A. References

A.1 Normative

[RFC2119]: RFC 2119 - Key words for use in RFCs to Indicate Requirement Levels

[RFC7159]: RFC 7159 - The JavaScript Object Notation (JSON) Data Interchange Format

[RFC4627]: RFC 4627 - The application/json Media Type for JavaScript Object Notation (JSON)

[RFC4288]: RFC 4288 - Media Type Specifications and Registration Procedures

[RFC2616]: RFC 2616 - Hypertext Transfer Protocol – HTTP/1.1

A.1 Informative

[TCP]: RFC 793 - Transmission Control Protocol

[Websockets]: RFC 6455 - The WebSocket Protocol