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7 Network Working Group D. Crockford
8 Request for Comments: 4627 JSON.org
9 Category: Informational July 2006
10
11
12 The application/json Media Type for JavaScript Object Notation (JSON)
13
14 Status of This Memo
15
16 This memo provides information for the Internet community. It does
17 not specify an Internet standard of any kind. Distribution of this
18 memo is unlimited.
19
20 Copyright Notice
21
22 Copyright (C) The Internet Society (2006).
23
24 Abstract
25
26 JavaScript Object Notation (JSON) is a lightweight, text-based,
27 language-independent data interchange format. It was derived from
28 the ECMAScript Programming Language Standard. JSON defines a small
29 set of formatting rules for the portable representation of structured
30 data.
31
32 1. Introduction
33
34 JavaScript Object Notation (JSON) is a text format for the
35 serialization of structured data. It is derived from the object
36 literals of JavaScript, as defined in the ECMAScript Programming
37 Language Standard, Third Edition [ECMA].
38
39 JSON can represent four primitive types (strings, numbers, booleans,
40 and null) and two structured types (objects and arrays).
41
42 A string is a sequence of zero or more Unicode characters [UNICODE].
43
44 An object is an unordered collection of zero or more name/value
45 pairs, where a name is a string and a value is a string, number,
46 boolean, null, object, or array.
47
48 An array is an ordered sequence of zero or more values.
49
50 The terms "object" and "array" come from the conventions of
51 JavaScript.
52
53 JSON's design goals were for it to be minimal, portable, textual, and
54 a subset of JavaScript.
55
56
57
58 Crockford Informational [Page 1]
59
60 RFC 4627 JSON July 2006
61
62
63 1.1. Conventions Used in This Document
64
65 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
66 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
67 document are to be interpreted as described in [RFC2119].
68
69 The grammatical rules in this document are to be interpreted as
70 described in [RFC4234].
71
72 2. JSON Grammar
73
74 A JSON text is a sequence of tokens. The set of tokens includes six
75 structural characters, strings, numbers, and three literal names.
76
77 A JSON text is a serialized object or array.
78
79 JSON-text = object / array
80
81 These are the six structural characters:
82
83 begin-array = ws %x5B ws ; [ left square bracket
84
85 begin-object = ws %x7B ws ; { left curly bracket
86
87 end-array = ws %x5D ws ; ] right square bracket
88
89 end-object = ws %x7D ws ; } right curly bracket
90
91 name-separator = ws %x3A ws ; : colon
92
93 value-separator = ws %x2C ws ; , comma
94
95 Insignificant whitespace is allowed before or after any of the six
96 structural characters.
97
98 ws = *(
99 %x20 / ; Space
100 %x09 / ; Horizontal tab
101 %x0A / ; Line feed or New line
102 %x0D ; Carriage return
103 )
104
105 2.1. Values
106
107 A JSON value MUST be an object, array, number, or string, or one of
108 the following three literal names:
109
110 false null true
111
112
113
114 Crockford Informational [Page 2]
115
116 RFC 4627 JSON July 2006
117
118
119 The literal names MUST be lowercase. No other literal names are
120 allowed.
121
122 value = false / null / true / object / array / number / string
123
124 false = %x66.61.6c.73.65 ; false
125
126 null = %x6e.75.6c.6c ; null
127
128 true = %x74.72.75.65 ; true
129
130 2.2. Objects
131
132 An object structure is represented as a pair of curly brackets
133 surrounding zero or more name/value pairs (or members). A name is a
134 string. A single colon comes after each name, separating the name
135 from the value. A single comma separates a value from a following
136 name. The names within an object SHOULD be unique.
137
138 object = begin-object [ member *( value-separator member ) ]
139 end-object
140
141 member = string name-separator value
142
143 2.3. Arrays
144
145 An array structure is represented as square brackets surrounding zero
146 or more values (or elements). Elements are separated by commas.
147
148 array = begin-array [ value *( value-separator value ) ] end-array
149
150 2.4. Numbers
151
152 The representation of numbers is similar to that used in most
153 programming languages. A number contains an integer component that
154 may be prefixed with an optional minus sign, which may be followed by
155 a fraction part and/or an exponent part.
156
157 Octal and hex forms are not allowed. Leading zeros are not allowed.
158
159 A fraction part is a decimal point followed by one or more digits.
160
161 An exponent part begins with the letter E in upper or lowercase,
162 which may be followed by a plus or minus sign. The E and optional
163 sign are followed by one or more digits.
164
165 Numeric values that cannot be represented as sequences of digits
166 (such as Infinity and NaN) are not permitted.
167
168
169
170 Crockford Informational [Page 3]
171
172 RFC 4627 JSON July 2006
173
174
175 number = [ minus ] int [ frac ] [ exp ]
176
177 decimal-point = %x2E ; .
178
179 digit1-9 = %x31-39 ; 1-9
180
181 e = %x65 / %x45 ; e E
182
183 exp = e [ minus / plus ] 1*DIGIT
184
185 frac = decimal-point 1*DIGIT
186
187 int = zero / ( digit1-9 *DIGIT )
188
189 minus = %x2D ; -
190
191 plus = %x2B ; +
192
193 zero = %x30 ; 0
194
195 2.5. Strings
196
197 The representation of strings is similar to conventions used in the C
198 family of programming languages. A string begins and ends with
199 quotation marks. All Unicode characters may be placed within the
200 quotation marks except for the characters that must be escaped:
201 quotation mark, reverse solidus, and the control characters (U+0000
202 through U+001F).
203
204 Any character may be escaped. If the character is in the Basic
205 Multilingual Plane (U+0000 through U+FFFF), then it may be
206 represented as a six-character sequence: a reverse solidus, followed
207 by the lowercase letter u, followed by four hexadecimal digits that
208 encode the character's code point. The hexadecimal letters A though
209 F can be upper or lowercase. So, for example, a string containing
210 only a single reverse solidus character may be represented as
211 "\u005C".
212
213 Alternatively, there are two-character sequence escape
214 representations of some popular characters. So, for example, a
215 string containing only a single reverse solidus character may be
216 represented more compactly as "\\".
217
218 To escape an extended character that is not in the Basic Multilingual
219 Plane, the character is represented as a twelve-character sequence,
220 encoding the UTF-16 surrogate pair. So, for example, a string
221 containing only the G clef character (U+1D11E) may be represented as
222 "\uD834\uDD1E".
223
224
225
226 Crockford Informational [Page 4]
227
228 RFC 4627 JSON July 2006
229
230
231 string = quotation-mark *char quotation-mark
232
233 char = unescaped /
234 escape (
235 %x22 / ; " quotation mark U+0022
236 %x5C / ; \ reverse solidus U+005C
237 %x2F / ; / solidus U+002F
238 %x62 / ; b backspace U+0008
239 %x66 / ; f form feed U+000C
240 %x6E / ; n line feed U+000A
241 %x72 / ; r carriage return U+000D
242 %x74 / ; t tab U+0009
243 %x75 4HEXDIG ) ; uXXXX U+XXXX
244
245 escape = %x5C ; \
246
247 quotation-mark = %x22 ; "
248
249 unescaped = %x20-21 / %x23-5B / %x5D-10FFFF
250
251 3. Encoding
252
253 JSON text SHALL be encoded in Unicode. The default encoding is
254 UTF-8.
255
256 Since the first two characters of a JSON text will always be ASCII
257 characters [RFC0020], it is possible to determine whether an octet
258 stream is UTF-8, UTF-16 (BE or LE), or UTF-32 (BE or LE) by looking
259 at the pattern of nulls in the first four octets.
260
261 00 00 00 xx UTF-32BE
262 00 xx 00 xx UTF-16BE
263 xx 00 00 00 UTF-32LE
264 xx 00 xx 00 UTF-16LE
265 xx xx xx xx UTF-8
266
267 4. Parsers
268
269 A JSON parser transforms a JSON text into another representation. A
270 JSON parser MUST accept all texts that conform to the JSON grammar.
271 A JSON parser MAY accept non-JSON forms or extensions.
272
273 An implementation may set limits on the size of texts that it
274 accepts. An implementation may set limits on the maximum depth of
275 nesting. An implementation may set limits on the range of numbers.
276 An implementation may set limits on the length and character contents
277 of strings.
278
279
280
281
282 Crockford Informational [Page 5]
283
284 RFC 4627 JSON July 2006
285
286
287 5. Generators
288
289 A JSON generator produces JSON text. The resulting text MUST
290 strictly conform to the JSON grammar.
291
292 6. IANA Considerations
293
294 The MIME media type for JSON text is application/json.
295
296 Type name: application
297
298 Subtype name: json
299
300 Required parameters: n/a
301
302 Optional parameters: n/a
303
304 Encoding considerations: 8bit if UTF-8; binary if UTF-16 or UTF-32
305
306 JSON may be represented using UTF-8, UTF-16, or UTF-32. When JSON
307 is written in UTF-8, JSON is 8bit compatible. When JSON is
308 written in UTF-16 or UTF-32, the binary content-transfer-encoding
309 must be used.
310
311 Security considerations:
312
313 Generally there are security issues with scripting languages. JSON
314 is a subset of JavaScript, but it is a safe subset that excludes
315 assignment and invocation.
316
317 A JSON text can be safely passed into JavaScript's eval() function
318 (which compiles and executes a string) if all the characters not
319 enclosed in strings are in the set of characters that form JSON
320 tokens. This can be quickly determined in JavaScript with two
321 regular expressions and calls to the test and replace methods.
322
323 var my_JSON_object = !(/[^,:{}\[\]0-9.\-+Eaeflnr-u \n\r\t]/.test(
324 text.replace(/"(\\.|[^"\\])*"/g, ''))) &&
325 eval('(' + text + ')');
326
327 Interoperability considerations: n/a
328
329 Published specification: RFC 4627
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335
336
337
338 Crockford Informational [Page 6]
339
340 RFC 4627 JSON July 2006
341
342
343 Applications that use this media type:
344
345 JSON has been used to exchange data between applications written
346 in all of these programming languages: ActionScript, C, C#,
347 ColdFusion, Common Lisp, E, Erlang, Java, JavaScript, Lua,
348 Objective CAML, Perl, PHP, Python, Rebol, Ruby, and Scheme.
349
350 Additional information:
351
352 Magic number(s): n/a
353 File extension(s): .json
354 Macintosh file type code(s): TEXT
355
356 Person & email address to contact for further information:
357 Douglas Crockford
358 douglas@crockford.com
359
360 Intended usage: COMMON
361
362 Restrictions on usage: none
363
364 Author:
365 Douglas Crockford
366 douglas@crockford.com
367
368 Change controller:
369 Douglas Crockford
370 douglas@crockford.com
371
372 7. Security Considerations
373
374 See Security Considerations in Section 6.
375
376 8. Examples
377
378 This is a JSON object:
379
380 {
381 "Image": {
382 "Width": 800,
383 "Height": 600,
384 "Title": "View from 15th Floor",
385 "Thumbnail": {
386 "Url": "http://www.example.com/image/481989943",
387 "Height": 125,
388 "Width": "100"
389 },
390 "IDs": [116, 943, 234, 38793]
391
392
393
394 Crockford Informational [Page 7]
395
396 RFC 4627 JSON July 2006
397
398
399 }
400 }
401
402 Its Image member is an object whose Thumbnail member is an object
403 and whose IDs member is an array of numbers.
404
405 This is a JSON array containing two objects:
406
407 [
408 {
409 "precision": "zip",
410 "Latitude": 37.7668,
411 "Longitude": -122.3959,
412 "Address": "",
413 "City": "SAN FRANCISCO",
414 "State": "CA",
415 "Zip": "94107",
416 "Country": "US"
417 },
418 {
419 "precision": "zip",
420 "Latitude": 37.371991,
421 "Longitude": -122.026020,
422 "Address": "",
423 "City": "SUNNYVALE",
424 "State": "CA",
425 "Zip": "94085",
426 "Country": "US"
427 }
428 ]
429
430 9. References
431
432 9.1. Normative References
433
434 [ECMA] European Computer Manufacturers Association, "ECMAScript
435 Language Specification 3rd Edition", December 1999,
436 <http://www.ecma-international.org/publications/files/
437 ecma-st/ECMA-262.pdf>.
438
439 [RFC0020] Cerf, V., "ASCII format for network interchange", RFC 20,
440 October 1969.
441
442 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
443 Requirement Levels", BCP 14, RFC 2119, March 1997.
444
445 [RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
446 Specifications: ABNF", RFC 4234, October 2005.
447
448
449
450 Crockford Informational [Page 8]
451
452 RFC 4627 JSON July 2006
453
454
455 [UNICODE] The Unicode Consortium, "The Unicode Standard Version 4.0",
456 2003, <http://www.unicode.org/versions/Unicode4.1.0/>.
457
458 Author's Address
459
460 Douglas Crockford
461 JSON.org
462 EMail: douglas@crockford.com
463
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506 Crockford Informational [Page 9]
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508 RFC 4627 JSON July 2006
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510
511 Full Copyright Statement
512
513 Copyright (C) The Internet Society (2006).
514
515 This document is subject to the rights, licenses and restrictions
516 contained in BCP 78, and except as set forth therein, the authors
517 retain all their rights.
518
519 This document and the information contained herein are provided on an
520 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
521 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
522 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
523 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
524 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
525 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
526
527 Intellectual Property
528
529 The IETF takes no position regarding the validity or scope of any
530 Intellectual Property Rights or other rights that might be claimed to
531 pertain to the implementation or use of the technology described in
532 this document or the extent to which any license under such rights
533 might or might not be available; nor does it represent that it has
534 made any independent effort to identify any such rights. Information
535 on the procedures with respect to rights in RFC documents can be
536 found in BCP 78 and BCP 79.
537
538 Copies of IPR disclosures made to the IETF Secretariat and any
539 assurances of licenses to be made available, or the result of an
540 attempt made to obtain a general license or permission for the use of
541 such proprietary rights by implementers or users of this
542 specification can be obtained from the IETF on-line IPR repository at
543 http://www.ietf.org/ipr.
544
545 The IETF invites any interested party to bring to its attention any
546 copyrights, patents or patent applications, or other proprietary
547 rights that may cover technology that may be required to implement
548 this standard. Please address the information to the IETF at
549 ietf-ipr@ietf.org.
550
551 Acknowledgement
552
553 Funding for the RFC Editor function is provided by the IETF
554 Administrative Support Activity (IASA).
555
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562 Crockford Informational [Page 10]
563
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