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Internet Engineering Task Force (IETF)                      T. Bray, Ed.Request for Comments: 8259                                    TextualityObsoletes:7159                                            December 2017Category: Standards TrackISSN: 2070-1721The JavaScript Object Notation (JSON) Data Interchange FormatAbstract   JavaScript Object Notation (JSON) is a lightweight, text-based,   language-independent data interchange format.  It was derived from   the ECMAScript Programming Language Standard.  JSON defines a small   set of formatting rules for the portable representation of structured   data.   This document removes inconsistencies with other specifications of   JSON, repairs specification errors, and offers experience-based   interoperability guidance.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttps://www.rfc-editor.org/info/rfc8259.Bray                         Standards Track                    [Page 1]

RFC 8259                          JSON                     December 2017Copyright Notice   Copyright (c) 2017 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (https://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.   This document may contain material from IETF Documents or IETF   Contributions published or made publicly available before November   10, 2008.  The person(s) controlling the copyright in some of this   material may not have granted the IETF Trust the right to allow   modifications of such material outside the IETF Standards Process.   Without obtaining an adequate license from the person(s) controlling   the copyright in such materials, this document may not be modified   outside the IETF Standards Process, and derivative works of it may   not be created outside the IETF Standards Process, except to format   it for publication as an RFC or to translate it into languages other   than English.Bray                         Standards Track                    [Page 2]

RFC 8259                          JSON                     December 2017Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .31.1.  Conventions Used in This Document . . . . . . . . . . . .41.2.  Specifications of JSON  . . . . . . . . . . . . . . . . .41.3.  Introduction to This Revision . . . . . . . . . . . . . .52.  JSON Grammar  . . . . . . . . . . . . . . . . . . . . . . . .53.  Values  . . . . . . . . . . . . . . . . . . . . . . . . . . .64.  Objects . . . . . . . . . . . . . . . . . . . . . . . . . . .65.  Arrays  . . . . . . . . . . . . . . . . . . . . . . . . . . .76.  Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . .77.  Strings . . . . . . . . . . . . . . . . . . . . . . . . . . .88.  String and Character Issues . . . . . . . . . . . . . . . . .98.1.  Character Encoding  . . . . . . . . . . . . . . . . . . .98.2.  Unicode Characters  . . . . . . . . . . . . . . . . . . .108.3.  String Comparison . . . . . . . . . . . . . . . . . . . .109.  Parsers . . . . . . . . . . . . . . . . . . . . . . . . . . .1010. Generators  . . . . . . . . . . . . . . . . . . . . . . . . .1011. IANA Considerations . . . . . . . . . . . . . . . . . . . . .1112. Security Considerations . . . . . . . . . . . . . . . . . . .1213. Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .1214. References  . . . . . . . . . . . . . . . . . . . . . . . . .1414.1.  Normative References . . . . . . . . . . . . . . . . . .1414.2.  Informative References . . . . . . . . . . . . . . . . .14Appendix A.  Changes fromRFC 7159  . . . . . . . . . . . . . . .16   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .16   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .161.  Introduction   JavaScript Object Notation (JSON) is a text format for the   serialization of structured data.  It is derived from the object   literals of JavaScript, as defined in the ECMAScript Programming   Language Standard, Third Edition [ECMA-262].   JSON can represent four primitive types (strings, numbers, booleans,   and null) and two structured types (objects and arrays).   A string is a sequence of zero or more Unicode characters [UNICODE].   Note that this citation references the latest version of Unicode   rather than a specific release.  It is not expected that future   changes in the Unicode specification will impact the syntax of JSON.   An object is an unordered collection of zero or more name/value   pairs, where a name is a string and a value is a string, number,   boolean, null, object, or array.   An array is an ordered sequence of zero or more values.Bray                         Standards Track                    [Page 3]

RFC 8259 JSON December 2017 The terms "object" and "array" come from the conventions of JavaScript. JSON's design goals were for it to be minimal, portable, textual, and a subset of JavaScript.1.1. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described inBCP14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. The grammatical rules in this document are to be interpreted as described in [RFC5234].1.2. Specifications of JSON This document replaces [RFC7159]. [RFC7159] obsoleted [RFC4627], which originally described JSON and registered the media type "application/json". JSON is also described in [ECMA-404]. The reference to ECMA-404 in the previous sentence is normative, not with the usual meaning that implementors need to consult it in order to understand this document, but to emphasize that there are no inconsistencies in the definition of the term "JSON text" in any of its specifications. Note, however, that ECMA-404 allows several practices that this specification recommends avoiding in the interests of maximal interoperability. The intent is that the grammar is the same between the two documents, although different descriptions are used. If there is a difference found between them, ECMA and the IETF will work together to update both documents. If an error is found with either document, the other should be examined to see if it has a similar error; if it does, it should be fixed, if possible. If either document is changed in the future, ECMA and the IETF will work together to ensure that the two documents stay aligned through the change.Bray Standards Track [Page 4]

RFC 8259                          JSON                     December 20171.3.  Introduction to This Revision   In the years since the publication ofRFC 4627, JSON has found very   wide use.  This experience has revealed certain patterns that, while   allowed by its specifications, have caused interoperability problems.   Also, a small number of errata have been reported regardingRFC 4627   (see RFC Errata IDs 607 [Err607] and 3607 [Err3607]) and regardingRFC 7159 (see RFC Errata IDs 3915 [Err3915], 4264 [Err4264], 4336   [Err4336], and 4388 [Err4388]).   This document's goal is to apply the errata, remove inconsistencies   with other specifications of JSON, and highlight practices that can   lead to interoperability problems.2.  JSON Grammar   A JSON text is a sequence of tokens.  The set of tokens includes six   structural characters, strings, numbers, and three literal names.   A JSON text is a serialized value.  Note that certain previous   specifications of JSON constrained a JSON text to be an object or an   array.  Implementations that generate only objects or arrays where a   JSON text is called for will be interoperable in the sense that all   implementations will accept these as conforming JSON texts.      JSON-text = ws value ws   These are the six structural characters:      begin-array     = ws %x5B ws  ; [ left square bracket      begin-object    = ws %x7B ws  ; { left curly bracket      end-array       = ws %x5D ws  ; ] right square bracket      end-object      = ws %x7D ws  ; } right curly bracket      name-separator  = ws %x3A ws  ; : colon      value-separator = ws %x2C ws  ; , commaBray                         Standards Track                    [Page 5]

RFC 8259 JSON December 2017 Insignificant whitespace is allowed before or after any of the six structural characters. ws = *( %x20 / ; Space %x09 / ; Horizontal tab %x0A / ; Line feed or New line %x0D ) ; Carriage return3. Values A JSON value MUST be an object, array, number, or string, or one of the following three literal names: false null true The literal names MUST be lowercase. No other literal names are allowed. value = false / null / true / object / array / number / string false = %x66.61.6c.73.65 ; false null = %x6e.75.6c.6c ; null true = %x74.72.75.65 ; true4. Objects An object structure is represented as a pair of curly brackets surrounding zero or more name/value pairs (or members). A name is a string. A single colon comes after each name, separating the name from the value. A single comma separates a value from a following name. The names within an object SHOULD be unique. object = begin-object [ member *( value-separator member ) ] end-object member = string name-separator value An object whose names are all unique is interoperable in the sense that all software implementations receiving that object will agree on the name-value mappings. When the names within an object are not unique, the behavior of software that receives such an object is unpredictable. Many implementations report the last name/value pair only. Other implementations report an error or fail to parse theBray Standards Track [Page 6]

RFC 8259                          JSON                     December 2017   object, and some implementations report all of the name/value pairs,   including duplicates.   JSON parsing libraries have been observed to differ as to whether or   not they make the ordering of object members visible to calling   software.  Implementations whose behavior does not depend on member   ordering will be interoperable in the sense that they will not be   affected by these differences.5.  Arrays   An array structure is represented as square brackets surrounding zero   or more values (or elements).  Elements are separated by commas.   array = begin-array [ value *( value-separator value ) ] end-array   There is no requirement that the values in an array be of the same   type.6.  Numbers   The representation of numbers is similar to that used in most   programming languages.  A number is represented in base 10 using   decimal digits.  It contains an integer component that may be   prefixed with an optional minus sign, which may be followed by a   fraction part and/or an exponent part.  Leading zeros are not   allowed.   A fraction part is a decimal point followed by one or more digits.   An exponent part begins with the letter E in uppercase or lowercase,   which may be followed by a plus or minus sign.  The E and optional   sign are followed by one or more digits.   Numeric values that cannot be represented in the grammar below (such   as Infinity and NaN) are not permitted.      number = [ minus ] int [ frac ] [ exp ]      decimal-point = %x2E       ; .      digit1-9 = %x31-39         ; 1-9      e = %x65 / %x45            ; e E      exp = e [ minus / plus ] 1*DIGIT      frac = decimal-point 1*DIGITBray                         Standards Track                    [Page 7]

RFC 8259 JSON December 2017 int = zero / ( digit1-9 *DIGIT ) minus = %x2D ; - plus = %x2B ; + zero = %x30 ; 0 This specification allows implementations to set limits on the range and precision of numbers accepted. Since software that implements IEEE 754 binary64 (double precision) numbers [IEEE754] is generally available and widely used, good interoperability can be achieved by implementations that expect no more precision or range than these provide, in the sense that implementations will approximate JSON numbers within the expected precision. A JSON number such as 1E400 or 3.141592653589793238462643383279 may indicate potential interoperability problems, since it suggests that the software that created it expects receiving software to have greater capabilities for numeric magnitude and precision than is widely available. Note that when such software is used, numbers that are integers and are in the range [-(2**53)+1, (2**53)-1] are interoperable in the sense that implementations will agree exactly on their numeric values.7. Strings The representation of strings is similar to conventions used in the C family of programming languages. A string begins and ends with quotation marks. All Unicode characters may be placed within the quotation marks, except for the characters that MUST be escaped: quotation mark, reverse solidus, and the control characters (U+0000 through U+001F). Any character may be escaped. If the character is in the Basic Multilingual Plane (U+0000 through U+FFFF), then it may be represented as a six-character sequence: a reverse solidus, followed by the lowercase letter u, followed by four hexadecimal digits that encode the character's code point. The hexadecimal letters A through F can be uppercase or lowercase. So, for example, a string containing only a single reverse solidus character may be represented as "\u005C". Alternatively, there are two-character sequence escape representations of some popular characters. So, for example, a string containing only a single reverse solidus character may be represented more compactly as "\\".Bray Standards Track [Page 8]

RFC 8259                          JSON                     December 2017   To escape an extended character that is not in the Basic Multilingual   Plane, the character is represented as a 12-character sequence,   encoding the UTF-16 surrogate pair.  So, for example, a string   containing only the G clef character (U+1D11E) may be represented as   "\uD834\uDD1E".      string = quotation-mark *char quotation-mark      char = unescaped /          escape (              %x22 /          ; "    quotation mark  U+0022              %x5C /          ; \    reverse solidus U+005C              %x2F /          ; /    solidus         U+002F              %x62 /          ; b    backspace       U+0008              %x66 /          ; f    form feed       U+000C              %x6E /          ; n    line feed       U+000A              %x72 /          ; r    carriage return U+000D              %x74 /          ; t    tab             U+0009              %x75 4HEXDIG )  ; uXXXX                U+XXXX      escape = %x5C              ; \      quotation-mark = %x22      ; "      unescaped = %x20-21 / %x23-5B / %x5D-10FFFF8.  String and Character Issues8.1.  Character Encoding   JSON text exchanged between systems that are not part of a closed   ecosystem MUST be encoded using UTF-8 [RFC3629].   Previous specifications of JSON have not required the use of UTF-8   when transmitting JSON text.  However, the vast majority of JSON-   based software implementations have chosen to use the UTF-8 encoding,   to the extent that it is the only encoding that achieves   interoperability.   Implementations MUST NOT add a byte order mark (U+FEFF) to the   beginning of a networked-transmitted JSON text.  In the interests of   interoperability, implementations that parse JSON texts MAY ignore   the presence of a byte order mark rather than treating it as an   error.Bray                         Standards Track                    [Page 9]

RFC 8259 JSON December 20178.2. Unicode Characters When all the strings represented in a JSON text are composed entirely of Unicode characters [UNICODE] (however escaped), then that JSON text is interoperable in the sense that all software implementations that parse it will agree on the contents of names and of string values in objects and arrays. However, the ABNF in this specification allows member names and string values to contain bit sequences that cannot encode Unicode characters; for example, "\uDEAD" (a single unpaired UTF-16 surrogate). Instances of this have been observed, for example, when a library truncates a UTF-16 string without checking whether the truncation split a surrogate pair. The behavior of software that receives JSON texts containing such values is unpredictable; for example, implementations might return different values for the length of a string value or even suffer fatal runtime exceptions.8.3. String Comparison Software implementations are typically required to test names of object members for equality. Implementations that transform the textual representation into sequences of Unicode code units and then perform the comparison numerically, code unit by code unit, are interoperable in the sense that implementations will agree in all cases on equality or inequality of two strings. For example, implementations that compare strings with escaped characters unconverted may incorrectly find that "a\\b" and "a\u005Cb" are not equal.9. Parsers A JSON parser transforms a JSON text into another representation. A JSON parser MUST accept all texts that conform to the JSON grammar. A JSON parser MAY accept non-JSON forms or extensions. An implementation may set limits on the size of texts that it accepts. An implementation may set limits on the maximum depth of nesting. An implementation may set limits on the range and precision of numbers. An implementation may set limits on the length and character contents of strings.10. Generators A JSON generator produces JSON text. The resulting text MUST strictly conform to the JSON grammar.Bray Standards Track [Page 10]

RFC 8259                          JSON                     December 201711.  IANA Considerations   The media type for JSON text is application/json.   Type name:  application   Subtype name:  json   Required parameters:  n/a   Optional parameters:  n/a   Encoding considerations:  binary   Security considerations:  SeeRFC 8259, Section 12   Interoperability considerations:  Described inRFC 8259   Published specification:RFC 8259   Applications that use this media type:      JSON has been used to exchange data between applications written      in all of these programming languages: ActionScript, C, C#,      Clojure, ColdFusion, Common Lisp, E, Erlang, Go, Java, JavaScript,      Lua, Objective CAML, Perl, PHP, Python, Rebol, Ruby, Scala, and      Scheme.   Additional information:      Magic number(s): n/a      File extension(s): .json      Macintosh file type code(s): TEXT   Person & email address to contact for further information:      IESG      <iesg@ietf.org>   Intended usage:  COMMON   Restrictions on usage:  none   Author:      Douglas Crockford      <douglas@crockford.com>   Change controller:      IESG      <iesg@ietf.org>Bray                         Standards Track                   [Page 11]

RFC 8259                          JSON                     December 2017   Note:  No "charset" parameter is defined for this registration.      Adding one really has no effect on compliant recipients.12.  Security Considerations   Generally, there are security issues with scripting languages.  JSON   is a subset of JavaScript but excludes assignment and invocation.   Since JSON's syntax is borrowed from JavaScript, it is possible to   use that language's "eval()" function to parse most JSON texts (but   not all; certain characters such as U+2028 LINE SEPARATOR and U+2029   PARAGRAPH SEPARATOR are legal in JSON but not JavaScript).  This   generally constitutes an unacceptable security risk, since the text   could contain executable code along with data declarations.  The same   consideration applies to the use of eval()-like functions in any   other programming language in which JSON texts conform to that   language's syntax.13.  Examples   This is a JSON object:      {        "Image": {            "Width":  800,            "Height": 600,            "Title":  "View from 15th Floor",            "Thumbnail": {                "Url":    "http://www.example.com/image/481989943",                "Height": 125,                "Width":  100            },            "Animated" : false,            "IDs": [116, 943, 234, 38793]          }      }   Its Image member is an object whose Thumbnail member is an object and   whose IDs member is an array of numbers.Bray                         Standards Track                   [Page 12]

RFC 8259                          JSON                     December 2017   This is a JSON array containing two objects:      [        {           "precision": "zip",           "Latitude":  37.7668,           "Longitude": -122.3959,           "Address":   "",           "City":      "SAN FRANCISCO",           "State":     "CA",           "Zip":       "94107",           "Country":   "US"        },        {           "precision": "zip",           "Latitude":  37.371991,           "Longitude": -122.026020,           "Address":   "",           "City":      "SUNNYVALE",           "State":     "CA",           "Zip":       "94085",           "Country":   "US"        }      ]   Here are three small JSON texts containing only values:   "Hello world!"   42   trueBray                         Standards Track                   [Page 13]

RFC 8259                          JSON                     December 201714.  References14.1.  Normative References   [ECMA-404] Ecma International, "The JSON Data Interchange Format",              Standard ECMA-404,              <http://www.ecma-international.org/publications/standards/Ecma-404.htm>.   [IEEE754]  IEEE, "IEEE Standard for Floating-Point Arithmetic",              IEEE 754.   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119,              DOI 10.17487/RFC2119, March 1997,              <https://www.rfc-editor.org/info/rfc2119>.   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO              10646", STD 63,RFC 3629, DOI 10.17487/RFC3629, November              2003, <https://www.rfc-editor.org/info/rfc3629>.   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax              Specifications: ABNF", STD 68,RFC 5234,              DOI 10.17487/RFC5234, January 2008,              <https://www.rfc-editor.org/info/rfc5234>.   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase inRFC2119 Key Words",BCP 14,RFC 8174, DOI 10.17487/RFC8174,              May 2017, <https://www.rfc-editor.org/info/rfc8174>.   [UNICODE]  The Unicode Consortium, "The Unicode Standard",              <http://www.unicode.org/versions/latest/>.14.2.  Informative References   [ECMA-262] Ecma International, "ECMAScript Language Specification",              Standard ECMA-262, Third Edition, December 1999,              <http://www.ecma-international.org/publications/files/              ECMA-ST-ARCH/              ECMA-262,%203rd%20edition,%20December%201999.pdf>.   [Err3607]  RFC Errata, Erratum ID 3607,RFC 4627,              <https://www.rfc-editor.org/errata/eid3607>.   [Err3915]  RFC Errata, Erratum ID 3915,RFC 7159,              <https://www.rfc-editor.org/errata/eid3915>.Bray                         Standards Track                   [Page 14]

RFC 8259                          JSON                     December 2017   [Err4264]  RFC Errata, Erratum ID 4264,RFC 7159,              <https://www.rfc-editor.org/errata/eid4264>.   [Err4336]  RFC Errata, Erratum ID 4336,RFC 7159,              <https://www.rfc-editor.org/errata/eid4336>.   [Err4388]  RFC Errata, Erratum ID 4388,RFC 7159,              <https://www.rfc-editor.org/errata/eid4388>.   [Err607]   RFC Errata, Erratum ID 607,RFC 4627,              <https://www.rfc-editor.org/errata/eid607>.   [RFC4627]  Crockford, D., "The application/json Media Type for              JavaScript Object Notation (JSON)",RFC 4627,              DOI 10.17487/RFC4627, July 2006,              <https://www.rfc-editor.org/info/rfc4627>.   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data              Interchange Format",RFC 7159, DOI 10.17487/RFC7159, March              2014, <https://www.rfc-editor.org/info/rfc7159>.Bray                         Standards Track                   [Page 15]

RFC 8259                          JSON                     December 2017Appendix A.  Changes fromRFC 7159   This section lists changes between this document and the text inRFC 7159.   oSection 1.2 has been updated to reflect the removal of a JSON      specification from ECMA-262, to make ECMA-404 a normative      reference, and to explain the particular meaning of "normative".   oSection 1.3 has been updated to reflect errata filed againstRFC 7159, notRFC 4627.   oSection 8.1 was changed to require the use of UTF-8 when      transmitted over a network.   oSection 12 has been updated to increase the precision of the      description of the security risk that follows from using the      ECMAScript "eval()" function.   oSection 14.1 has been updated to include ECMA-404 as a normative      reference.   oSection 14.2 has been updated to remove ECMA-404, update the      version of ECMA-262, and refresh the errata list.ContributorsRFC 4627 was written by Douglas Crockford.  This document was   constructed by making a relatively small number of changes to that   document; thus, the vast majority of the text here is his.Author's Address   Tim Bray (editor)   Textuality   Email: tbray@textuality.comBray                         Standards Track                   [Page 16]

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