ISO/IEC 21778:2017

INTERNATIONAL ISO/IEC
STANDARD 21778
First edition
2017-11
Information technology — The JSON
data interchange syntax
Technologies de l'information — Syntaxe d'échange de données JSON
Reference number
©
ISO/IEC 2017
© ISO/IEC 2017, Published in Switzerland
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ii © ISO/IEC 2017 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Conformance . 1
3 Normative References . 1
4 JSON Text . 1
5 JSON Values . 2
6 Objects . 2
7 Arrays . 3
8 Numbers . 3
9 String . 4
Bibliography . 6
© ISO/IEC 2017 – All rights reserved iii

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work. In the field of information technology, ISO and IEC have established a joint technical committee,
ISO/IEC JTC 1.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for
the different types of document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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URL: www.iso.org/iso/foreword.html.
ISO/IEC 21778 was prepared by Ecma International (as ECMA‐404) and was adopted, under a special
"fast‐track procedure", by Joint Technical Committee ISO/IEC JTC 1, Information technology, in parallel
with its approval by national bodies of ISO and IEC.
iv © ISO/IEC 2017 – All rights reserved

Introduction
1)
JSON is a text syntax that facilitates structured data interchange between all programming
languages. JSON is a syntax of braces, brackets, colons, and commas that is useful in many contexts,
profiles, and applications. JSON stands for JavaScript Object Notation and was inspired by the object
literals of JavaScript aka ECMAScript as defined in the ECMAScript Language Specification, Third
[1]
Edition. However, it does not attempt to impose ECMAScript’s internal data representations on
other programming languages. Instead, it shares a small subset of ECMAScript’s syntax with all
other programming languages. The JSON syntax is not a specification of a complete data interchange.
Meaningful data interchange requires agreement between a producer and consumer on the semantics
attached to a particular use of the JSON syntax. What JSON does provide is the syntactic framework to
which such semantics can be attached
JSON syntax describes a sequence of Unicode code points. JSON also depends on Unicode in the hex
numbers used in the \u escapement notation.
JSON is agnostic about the semantics of numbers. In any programming language, there can be a variety
of number types of various capacities and complements, fixed or floating, binary or decimal. That can
make interchange between different programming languages difficult. JSON instead offers only the
representation of numbers that humans use: a sequence of digits. All programming languages know
how to make sense of digit sequences even if they disagree on internal representations. That is enough
to allow interchange.
Programming languages vary widely on whether they support objects, and if so, what characteristics
and constraints the objects offer. The models of object systems can be wildly divergent and are
continuing to evolve. JSON instead provides a simple notation for expressing collections of name/value
pairs. Most programming languages will have some feature for representing such collections, which
can go by names like record, struct, dict, map, hash, or object.
JSON also provides support for ordered lists of values. All programming languages will have some
feature for representing such lists, which can go by names like array, vector, or list. Because
objects and arrays can nest, trees and other complex data structures can be represented. By accepting
JSON’s simple convention, complex data structures can be easily interchanged between incompatible
programming languages.
JSON does not support cyclic graphs, at least not directly. JSON is not indicated for applications requiring
binary data.
It is expected that other standards will refer to this one, strictly adhering to the JSON syntax, while
imposing semantics interpretation and restrictions on various encoding details. Such standards may
require specific behaviours. JSON itself specifies no behaviour.
Because it is so simple, it is not expected that the JSON grammar will ever change. This gives JSON, as a
foundational notation, tremendous stability.
JSON was first
...