JSON Schema (application/schema+json) has several purposes, one of which is JSON instance validation. This document specifies a vocabulary for JSON Schema to describe the meaning of JSON documents, provide hints for user interfaces working with JSON data, and to make assertions about what a valid document must look like.
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JSON Schema can be used to require that a given JSON document (an instance) satisfies a certain number of criteria. These criteria are asserted by using keywords described in this specification. In addition, a set of keywords is also defined to assist in interactive user interface instance generation.
This specification will use the concepts, syntax, and terminology defined by the JSON Schema core specification.
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.
This specification uses the term "container instance" to refer to both array and object instances. It uses the term "children instances" to refer to array elements or object member values.
Elements in an array value are said to be unique if no two elements of this array are equal.
JSON Schema validation asserts constraints on the structure of instance data. An instance location that satisfies all asserted constraints is then annotated with any keywords that contain non-assertion information, such as descriptive metadata and usage hints. If all locations within the instance satisfy all asserted constraints, then the instance is said to be valid against the schema.
Each schema object is independently evaluated against each instance location to which it applies. This greatly simplifies the implementation requirements for validators by ensuring that they do not need to maintain state across the document-wide validation process.
This specification defines a set of assertion keywords, as well as a small vocabulary of metadata keywords that can be used to annotate the JSON instance with useful information. The {{format}} keyword is intended primarily as an annotation, but can optionally be used as an assertion. The {{content}} keywords are annotations for working with documents embedded as JSON strings.
It should be noted that the nul character (\u0000) is valid in a JSON string. An instance to validate may contain a string value with this character, regardless of the ability of the underlying programming language to deal with such data.
The JSON specification allows numbers with arbitrary precision, and JSON Schema does not add any such bounds. This means that numeric instances processed by JSON Schema can be arbitrarily large and/or have an arbitrarily long decimal part, regardless of the ability of the underlying programming language to deal with such data.
Keywords that use regular expressions, or constrain the instance value to be a regular expression, are subject to the interoperability considerations for regular expressions in the JSON Schema Core specification.
The current IRI for the default JSON Schema dialect meta-schema is
https://json-schema.org/draft/next/schema. For schema author convenience, this
meta-schema describes a dialect consisting of all vocabularies defined in this
specification and the JSON Schema Core specification, as well as two former
keywords which are reserved for a transitional period. Individual vocabulary and
vocabulary meta-schema IRIs are given for each section below. Certain
vocabularies are optional to support, which is explained in detail in the
relevant sections.
Updated vocabulary and meta-schema IRIs MAY be published between specification drafts in order to correct errors. Implementations SHOULD consider IRIs dated after this specification draft and before the next to indicate the same syntax and semantics as those listed here.
Validation keywords in a schema impose requirements for successful validation of an instance. These keywords are all assertions without any annotation behavior.
Meta-schemas that do not use $vocabulary SHOULD be considered to require this
vocabulary as if its IRI were present with a value of true.
The current IRI for this vocabulary, known as the Validation vocabulary, is:
https://json-schema.org/draft/next/vocab/validation.
The current IRI for the corresponding meta-schema is:
https://json-schema.org/draft/next/meta/validation.
The value of this keyword MUST be either a string or an array. If it is an array, elements of the array MUST be strings and MUST be unique.
String values MUST be one of the six primitive types ("null", "boolean", "object", "array", "number", or "string"), or "integer" which matches any number with a zero fractional part.
If the value of type is a string, then an instance validates successfully if
its type matches the type represented by the value of the string.
If the value of type is an array, then an instance validates successfully if
its type matches any of the types indicated by the strings in the array.
The value of this keyword MUST be an array. This array SHOULD have at least one element. Elements in the array SHOULD be unique.
An instance validates successfully against this keyword if its value is equal to one of the elements in this keyword's array value.
Elements in the array might be of any type, including null.
The value of this keyword MAY be of any type, including null.
Use of this keyword is functionally equivalent to an enum with a
single value.
An instance validates successfully against this keyword if its value is equal to the value of the keyword.
The value of multipleOf MUST be a number, strictly greater than 0.
A numeric instance is valid only if division by this keyword's value results in an integer.
The value of maximum MUST be a number, representing an inclusive upper limit
for a numeric instance.
If the instance is a number, then this keyword validates only if the instance is
less than or exactly equal to maximum.
The value of exclusiveMaximum MUST be a number, representing an exclusive
upper limit for a numeric instance.
If the instance is a number, then the instance is valid only if it has a value
strictly less than (not equal to) exclusiveMaximum.
The value of minimum MUST be a number, representing an inclusive lower limit
for a numeric instance.
If the instance is a number, then this keyword validates only if the instance is
greater than or exactly equal to minimum.
The value of exclusiveMinimum MUST be a number, representing an exclusive
lower limit for a numeric instance.
If the instance is a number, then the instance is valid only if it has a value
strictly greater than (not equal to) exclusiveMinimum.
The value of this keyword MUST be a non-negative integer.
A string instance is valid against this keyword if its length is less than, or equal to, the value of this keyword.
The length of a string instance is defined as the number of its characters as defined by RFC 8259.
The value of this keyword MUST be a non-negative integer.
A string instance is valid against this keyword if its length is greater than, or equal to, the value of this keyword.
The length of a string instance is defined as the number of its characters as defined by RFC 8259.
Omitting this keyword has the same behavior as a value of 0.
The value of this keyword MUST be a string. This string SHOULD be a valid regular expression, according to the ECMA-262 regular expression dialect.
A string instance is considered valid if the regular expression matches the instance successfully. Recall: regular expressions are not implicitly anchored.
The value of this keyword MUST be a non-negative integer.
An array instance is valid against maxItems if its size is less than, or equal
to, the value of this keyword.
The value of this keyword MUST be a non-negative integer.
An array instance is valid against minItems if its size is greater than, or
equal to, the value of this keyword.
Omitting this keyword has the same behavior as a value of 0.
The value of this keyword MUST be a boolean.
If this keyword has boolean value false, the instance validates successfully. If it has boolean value true, the instance validates successfully if all of its elements are unique.
Omitting this keyword has the same behavior as a value of false.
The value of this keyword MUST be a non-negative integer.
An object instance is valid against maxProperties if its number of properties
is less than, or equal to, the value of this keyword.
The value of this keyword MUST be a non-negative integer.
An object instance is valid against minProperties if its number of properties
is greater than, or equal to, the value of this keyword.
Omitting this keyword has the same behavior as a value of 0.
The value of this keyword MUST be an array. Elements of this array, if any, MUST be strings, and MUST be unique.
An object instance is valid against this keyword if every item in the array is the name of a property in the instance.
Omitting this keyword has the same behavior as an empty array.
The value of this keyword MUST be an object. Properties in this object, if any, MUST be arrays. Elements in each array, if any, MUST be strings, and MUST be unique.
This keyword specifies properties that are required if a specific other property is present. Their requirement is dependent on the presence of the other property.
Validation succeeds if, for each name that appears in both the instance and as a name within this keyword's value, every item in the corresponding array is also the name of a property in the instance.
Omitting this keyword has the same behavior as an empty object.
Structural validation alone may be insufficient to allow an application to
correctly utilize certain values. The format annotation keyword is defined to
allow schema authors to convey semantic information for a fixed subset of values
which are accurately described by authoritative resources, be they RFCs or other
external specifications.
The value of this keyword is called a format attribute. It MUST be a string. A format attribute can generally only validate a given set of instance types. If the type of the instance to validate is not in this set, validation for this format attribute and instance SHOULD succeed. All format attributes defined in this section apply to strings, but a format attribute can be specified to apply to any instance types defined in the data model defined in the core JSON Schema.1
The current IRI for this vocabulary, known as the Format-Annotation vocabulary,
is: https://json-schema.org/draft/next/vocab/format-annotation. The current
IRI for the corresponding meta-schema is:
https://json-schema.org/draft/next/meta/format-annotation. Implementing
support for this vocabulary is REQUIRED.
In addition to the Format-Annotation vocabulary, a secondary vocabulary is
available for custom meta-schemas that defines format as an assertion. The IRI
for the Format-Assertion vocabulary, is:
https://json-schema.org/draft/next/vocab/format-assertion. The current IRI for
the corresponding meta-schema is:
https://json-schema.org/draft/next/meta/format-assertion. Implementing support
for the Format-Assertion vocabulary is OPTIONAL.
Specifying both the Format-Annotation and the Format-Assertion vocabularies is functionally equivalent to specifying only the Format-Assertion vocabulary since its requirements are a superset of the Format-Annotation vocabulary.
The format keyword functions as defined by the vocabulary which is referenced.
The value of format MUST be collected as an annotation, if the implementation supports annotation collection. This enables application-level validation when schema validation is unavailable or inadequate.
Implementations MAY still treat format as an assertion in addition to an
annotation and attempt to validate the value's conformance to the specified
semantics. The implementation MUST provide options to enable and disable such
evaluation and MUST be disabled by default. Implementations SHOULD document
their level of support for such validation.2
When the implementation is configured for assertion behavior, it:
- SHOULD provide an implementation-specific best effort validation for each format attribute defined below;
- MAY choose to implement validation of any or all format attributes as a no-op by always producing a validation result of true;3
When the Format-Assertion vocabulary is declared with a value of true, implementations MUST provide full validation support for all of the formats defined by this specification. Implementations that cannot provide full validation support MUST refuse to process the schema.
An implementation that supports the Format-Assertion vocabulary:
- MUST still collect
formatas an annotation if the implementation supports annotation collection; - MUST evaluate
formatas an assertion; - MUST implement syntactic validation for all format attributes defined in this specification, and for any additional format attributes that it recognizes, such that there exist possible instance values of the correct type that will fail validation.
The requirement for minimal validation of format attributes is intentionally vague and permissive, due to the complexity involved in many of the attributes. Note in particular that the requirement is limited to syntactic checking; it is not to be expected that an implementation would send an email, attempt to connect to a URL, or otherwise check the existence of an entity identified by a format instance.4
It is RECOMMENDED that implementations use a common parsing library for each format, or a well-known regular expression. Implementations SHOULD clearly document how and to what degree each format attribute is validated.
The standard core and validation meta-schema includes this
vocabulary in its $vocabulary keyword with a value of false, since by default
implementations are not required to support this keyword as an assertion.
Supporting the format vocabulary with a value of true is understood to greatly
increase code size and in some cases execution time, and will not be appropriate
for all implementations.
Implementations MAY support custom format attributes. Save for agreement between parties, schema authors SHALL NOT expect a peer implementation to support such custom format attributes. An implementation MUST NOT fail to collect unknown formats as annotations. When the Format-Assertion vocabulary is specified, implementations MUST fail upon encountering unknown formats.
Vocabularies do not support specifically declaring different value sets for keywords. Due to this limitation, and the historically uneven implementation of this keyword, it is RECOMMENDED to define additional keywords in a custom vocabulary rather than additional format attributes if interoperability is desired.
These attributes apply to string instances.
Date and time format names are derived from RFC 3339, section 5.6. The duration format is from the ISO 8601 ABNF as given in Appendix A of RFC 3339.
Implementations supporting formats SHOULD implement support for the following attributes:
- date-time: A string instance is valid against this attribute if it is a valid representation according to the "date-time" ABNF rule (referenced above)
- date: A string instance is valid against this attribute if it is a valid representation according to the "full-date" ABNF rule (referenced above)
- time: A string instance is valid against this attribute if it is a valid representation according to the "full-time" ABNF rule (referenced above)
- duration: A string instance is valid against this attribute if it is a valid representation according to the "duration" ABNF rule (referenced above)
Implementations MAY support additional attributes using the other format names defined anywhere in that RFC. If "full-date" or "full-time" are implemented, the corresponding short form ("date" or "time" respectively) MUST be implemented, and MUST behave identically. Implementations SHOULD NOT define extension attributes with any name matching an RFC 3339 format unless it validates according to the rules of that format.5
These attributes apply to string instances.
A string instance is valid against these attributes if it is a valid Internet email address as follows:
- email: As defined by the "Mailbox" ABNF rule in RFC 5321, section 4.1.2.
- idn-email: As defined by the extended "Mailbox" ABNF rule in RFC 6531, section 3.3. Note that all strings valid against the "email" attribute are also valid against the "idn-email" attribute.
These attributes apply to string instances.
A string instance is valid against these attributes if it is a valid representation for an Internet hostname as follows:
- hostname: As defined by RFC 1123, section 2.1, including host names produced using the Punycode algorithm specified in RFC 5891, section 4.4.
- idn-hostname: As defined by either RFC 1123 as for hostname, or an internationalized hostname as defined by RFC 5890, section 2.3.2.3. Note that all strings valid against the "hostname" attribute are also valid against the "idn-hostname" attribute.
These attributes apply to string instances.
A string instance is valid against these attributes if it is a valid representation of an IP address as follows:
- ipv4: An IPv4 address according to the "dotted-quad" ABNF syntax as defined in RFC 2673, section 3.2.
- ipv6: An IPv6 address as defined in RFC 4291, section 2.2.
- uri: A string instance is valid against this attribute if it is a valid IRI, according to RFC3987.
- uri-reference: A string instance is valid against this attribute if it is a valid URI Reference (either a URI or a relative-reference), according to RFC3986.
- iri: A string instance is valid against this attribute if it is a valid IRI, according to RFC3987.
- iri-reference: A string instance is valid against this attribute if it is a valid IRI Reference (either an IRI or a relative-reference), according to RFC3987.
- uuid: A string instance is valid against this attribute if it is a valid string representation of a UUID, according to RFC4122.
Note that all valid URIs are valid IRIs, and all valid URI References are also valid IRI References.
Note also that the "uuid" format is for plain UUIDs, not UUIDs in URNs. An example is "f81d4fae-7dec-11d0-a765-00a0c91e6bf6". For UUIDs as URNs, use the "uri" format, with a "pattern" regular expression of "^urn:uuid:" to indicate the URI scheme and URN namespace.
This attribute applies to string instances.
A string instance is valid against this attribute if it is a valid URI Template (of any level), according to RFC6570.
Note that URI Templates may be used for IRIs; there is no separate IRI Template specification.
These attributes apply to string instances.
- json-pointer: A string instance is valid against this attribute if it is a valid JSON string representation of a JSON Pointer, according to RFC 6901, section 5.
- relative-json-pointer: A string instance is valid against this attribute if
it is a valid Relative JSON Pointer. To allow for
both absolute and relative JSON Pointers, use
anyOforoneOfto indicate support for either format.
This attribute applies to string instances.
A regular expression, which SHOULD be valid according to the ECMA-262 regular expression dialect.
Implementations that validate formats MUST accept at least the subset of ECMA-262 defined in {{regexinterop}}), and SHOULD accept all valid ECMA-262 expressions.
Annotations defined in this section indicate that an instance contains non-JSON data encoded in a JSON string.
These properties provide additional information required to interpret JSON data as rich multimedia documents. They describe the type of content, how it is encoded, and/or how it may be validated. They do not function as validation assertions; a malformed string-encoded document MUST NOT cause the containing instance to be considered invalid.
Meta-schemas that do not use $vocabulary SHOULD be considered to require this
vocabulary as if its IRI were present with a value of true.
The current IRI for this vocabulary, known as the Content vocabulary, is:
https://json-schema.org/draft/next/vocab/content.
The current IRI for the corresponding meta-schema is:
https://json-schema.org/draft/next/meta/content.
Due to security and performance concerns, as well as the open-ended nature of possible content types, implementations MUST NOT automatically decode, parse, and/or validate the string contents. Applications are expected to use these annotations to invoke the appropriate libraries separately.
All keywords in this section apply only to strings, and have no effect on other data types.
If the instance value is a string, this property defines that the string SHOULD be interpreted as encoded binary data and applications wishing to decode it SHOULD do so using the encoding named by this property.
Possible values indicating base 16, 32, and 64 encodings with several variations are listed in RFC 4648. Additionally, sections 6.7 and 6.8 of RFC 2045 provide encodings used in MIME. This keyword is derived from MIME's Content-Transfer-Encoding header, which was designed to map binary data into ASCII characters. It is not related to HTTP's Content-Encoding header, which is used to encode (e.g. compress or encrypt) the content of HTTP request and responses.
As "base64" is defined in both RFCs, the definition from RFC 4648 SHOULD be assumed unless the string is specifically intended for use in a MIME context. Note that all of these encodings result in strings consisting only of 7-bit ASCII characters. Therefore, this keyword has no meaning for strings containing characters outside of that range.
If this keyword is absent, but contentMediaType is present, this indicates
that the encoding is the identity encoding, meaning that no transformation was
needed in order to represent the content in a UTF-8 string.
The value of this property MUST be a string.
If the instance is a string, this property indicates the media type of the
contents of the string. If contentEncoding is present, this property describes
the decoded string.
The value of this property MUST be a string, which MUST be a media type, as defined by RFC 2046.
If the instance is a string, and if contentMediaType is present, this property
contains a schema which describes the structure of the string.
This keyword MAY be used with any media type that can be mapped into JSON Schema's data model. Specifying such mappings is outside of the scope of this specification.
The value of this property MUST be a valid JSON schema. It SHOULD be ignored if
contentMediaType is not present. Accessing the schema through the schema
location IRI included as part of the annotation will ensure that it is correctly
processed as a subschema. Using the extracted annotation value directly is only
safe if the schema is an embedded resource with both $schema and an
absolute-IRI $id.
Here is an example schema, illustrating the use of contentEncoding and
contentMediaType:
{
"type": "string",
"contentEncoding": "base64",
"contentMediaType": "image/png"
}
Instances described by this schema are expected to be strings, and their values should be interpretable as base64-encoded PNG images.
Another example:
{
"type": "string",
"contentMediaType": "text/html"
}
Instances described by this schema are expected to be strings containing HTML, using whatever character set the JSON string was decoded into. Per section 8.1 of RFC 8259, outside of an entirely closed system, this MUST be UTF-8.
This example describes a JWT that is MACed using the HMAC SHA-256 algorithm, and requires the "iss" and "exp" fields in its claim set.
{
"type": "string",
"contentMediaType": "application/jwt",
"contentSchema": {
"type": "array",
"minItems": 2,
"prefixItems": [
{
"const": {
"typ": "JWT",
"alg": "HS256"
}
},
{
"type": "object",
"required": ["iss", "exp"],
"properties": {
"iss": {"type": "string"},
"exp": {"type": "integer"}
}
}
]
}
}
Note that contentEncoding does not appear. While the application/jwt media
type makes use of base64url encoding, that is defined by the media type, which
determines how the JWT string is decoded into a list of two JSON data
structures: first the header, and then the payload. Since the JWT media type
ensures that the JWT can be represented in a JSON string, there is no need for
further encoding or decoding.
keywords provide commonly used information for documentation and user interface display purposes. They are not intended to form a comprehensive set of features. Rather, additional vocabularies can be defined for more complex annotation-based applications.
Meta-schemas that do not use $vocabulary SHOULD be considered to require this
vocabulary as if its IRI were present with a value of true.
The current IRI for this vocabulary, known as the Meta-Data vocabulary, is:
https://json-schema.org/draft/next/vocab/meta-data.
The current IRI for the corresponding meta-schema is:
https://json-schema.org/draft/next/meta/meta-data.
The value of both of these keywords MUST be a string.
Both of these keywords can be used to decorate a user interface with information about the data produced by this user interface. A title will preferably be short, whereas a description will provide explanation about the purpose of the instance described by this schema.
There are no restrictions placed on the value of this keyword. When multiple occurrences of this keyword are applicable to a single sub-instance, implementations SHOULD remove duplicates.
This keyword can be used to supply a default JSON value associated with a particular schema. It is RECOMMENDED that a default value be valid against the associated schema.
The value of this keyword MUST be a boolean. When multiple occurrences of this keyword are applicable to a single sub-instance, applications SHOULD consider the instance location to be deprecated if any occurrence specifies a true value.
If deprecated has a value of boolean true, it indicates that applications
SHOULD refrain from usage of the declared property. It MAY mean the property is
going to be removed in the future.
A root schema containing deprecated with a value of true indicates that the
entire resource being described MAY be removed in the future.
The deprecated keyword applies to each instance location to which the schema
object containing the keyword successfully applies. This can result in scenarios
where every array item or object property is deprecated even though the
containing array or object is not.
Omitting this keyword has the same behavior as a value of false.
The value of these keywords MUST be a boolean. When multiple occurrences of these keywords are applicable to a single sub-instance, the resulting behavior SHOULD be as for a true value if any occurrence specifies a true value, and SHOULD be as for a false value otherwise.
If readOnly has a value of boolean true, it indicates that the value of the
instance is managed exclusively by the owning authority, and attempts by an
application to modify the value of this property are expected to be ignored or
rejected by that owning authority.
An instance document that is marked as readOnly for the entire document MAY be
ignored if sent to the owning authority, or MAY result in an error, at the
authority's discretion.
If writeOnly has a value of boolean true, it indicates that the value is never
present when the instance is retrieved from the owning authority. It can be
present when sent to the owning authority to update or create the document (or
the resource it represents), but it will not be included in any updated or newly
created version of the instance.
An instance document that is marked as writeOnly for the entire document MAY
be returned as a blank document of some sort, or MAY produce an error upon
retrieval, or have the retrieval request ignored, at the authority's discretion.
For example, readOnly would be used to mark a database-generated serial number
as read-only, while writeOnly would be used to mark a password input field.
These keywords can be used to assist in user interface instance generation. In particular, an application MAY choose to use a widget that hides input values as they are typed for write-only fields.
Omitting these keywords has the same behavior as values of false.
The value of this keyword MUST be an array. There are no restrictions placed on the values within the array. When multiple occurrences of this keyword are applicable to a single sub-instance, implementations MUST provide a flat array of all values rather than an array of arrays.
This keyword can be used to provide sample JSON values associated with a particular schema, for the purpose of illustrating usage. It is RECOMMENDED that these values be valid against the associated schema.
Implementations MAY use the value(s) of default, if present, as an additional
example. If examples is absent, default MAY still be used in this manner.
JSON Schema validation defines a vocabulary for JSON Schema core and concerns all the security considerations listed there.
JSON Schema validation allows the use of Regular Expressions, which have numerous different (often incompatible) implementations. Some implementations allow the embedding of arbitrary code, which is outside the scope of JSON Schema and MUST NOT be permitted. Regular expressions can often also be crafted to be extremely expensive to compute (with so-called "catastrophic backtracking"), resulting in a denial-of-service attack.
Implementations that support validating or otherwise evaluating instance string
data based on contentEncoding and/or contentMediaType are at risk of
evaluating data in an unsafe way based on misleading information. Applications
can mitigate this risk by only performing such processing when a relationship
between the schema and instance is established (e.g., they share the same
authority).
Processing a media type or encoding is subject to the security considerations of that media type or encoding. For example, the security considerations of RFC 4329 Scripting Media Types apply when processing JavaScript or ECMAScript encoded within a JSON string.
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Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996, <https://www.rfc-editor.org/info/rfc2045>.
Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, DOI 10.17487/RFC2046, November 1996, <https://www.rfc-editor.org/info/rfc2046>.
Crawford, M., "Binary Labels in the Domain Name System", RFC 2673, DOI 10.17487/RFC2673, August 1999, <https://www.rfc-editor.org/info/rfc2673>.
Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, <https://www.rfc-editor.org/info/rfc3339>.
Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, <https://www.rfc-editor.org/info/rfc3986>.
Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987, January 2005, <https://www.rfc-editor.org/info/rfc3987>.
Leach, P., Mealling, M., and R. Salz, "A Universally Unique IDentifier (UUID) URN Namespace", RFC 4122, DOI 10.17487/RFC4122, July 2005, <https://www.rfc-editor.org/info/rfc4122>.
Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, <https://www.rfc-editor.org/info/rfc4291>.
Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, <https://www.rfc-editor.org/info/rfc4648>.
Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, DOI 10.17487/RFC5321, October 2008, <https://www.rfc-editor.org/info/rfc5321>.
Klensin, J., "Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework", RFC 5890, DOI 10.17487/RFC5890, August 2010, <https://www.rfc-editor.org/info/rfc5890>.
Klensin, J., "Internationalized Domain Names in Applications (IDNA): Protocol", RFC 5891, DOI 10.17487/RFC5891, August 2010, <https://www.rfc-editor.org/info/rfc5891>.
Gregorio, J., Fielding, R., Hadley, M., Nottingham, M., and D. Orchard, "URI Template", RFC 6570, DOI 10.17487/RFC6570, March 2012, <https://www.rfc-editor.org/info/rfc6570>.
Yao, J. and W. Mao, "SMTP Extension for Internationalized Email", RFC 6531, DOI 10.17487/RFC6531, February 2012, <https://www.rfc-editor.org/info/rfc6531>.
Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed., "JavaScript Object Notation (JSON) Pointer", RFC 6901, DOI 10.17487/RFC6901, April 2013, <https://www.rfc-editor.org/info/rfc6901>.
Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017, <https://www.rfc-editor.org/info/rfc8259>.
ECMA-262, 11th edition specification", June 2020, <https://www.ecma-international.org/ecma-262/11.0>.
Luff, G., Andrews, H., and B. Hutton, Ed., "Relative JSON Pointers", Work in Progress, Internet-Draft, draft-handrews-relative-json-pointer-01, December 2020, <https://datatracker.ietf.org/doc/html/draft-handrews-relative-json-pointer-01>.
Wright, A., Andrews, H., Hutton, B., and G. Dennis, "JSON Schema: A Media Type for Describing JSON Documents", Work in Progress, Internet-Draft, draft-bhutton-json-schema-01, June 2022, <https://datatracker.ietf.org/doc/html/draft-bhutton-json-schema-01>.
Hoehrmann, B., "Scripting Media Types", RFC 4329, DOI 10.17487/RFC4329, April 2006, <https://www.rfc-editor.org/info/rfc4329>.
Several keywords have been moved from this document into the Core Specification starting with draft 2019-09, in some cases with re-naming or other changes. This affects the following former validation keywords:
definitionsRenamed to$defsto match$refand be shorter to type. Schema vocabulary authors SHOULD NOT define adefinitionskeyword with different behavior in order to avoid invalidating schemas that still use the older name. Whiledefinitionsis absent in the single-vocabulary meta-schemas referenced by this document, it remains present in the default meta-schema, and implementations SHOULD assume that$defsanddefinitionshave the same behavior when that meta-schema is used.allOf,anyOf,oneOf,not,if,then,else,items,additionalItems,contains,propertyNames,properties,patternProperties,additionalPropertiesAll of these keywords apply subschemas to the instance and combine their results, without asserting any conditions of their own. Without assertion keywords, these applicators can only cause assertion failures by using the false boolean schema, or by inverting the result of the true boolean schema (or equivalent schema objects). For this reason, they are better defined as a generic mechanism on which validation, hyper-schema, and extension vocabularies can all be based.maxContains,minContainsThese keywords modify the behavior ofcontains, and are therefore grouped with it in the applicator vocabulary.dependenciesThis keyword had two different modes of behavior, which made it relatively challenging to implement and reason about. The schema form has been moved to Core and renamed todependentSchemas, as part of the applicator vocabulary. It is analogous toproperties, except that instead of applying its subschema to the property value, it applies it to the object containing the property. The property name array form is retained here and renamed todependentRequired, as it is an assertion which is a shortcut for the conditional use of therequiredassertion keyword.
Thanks to Gary Court, Francis Galiegue, Kris Zyp, Geraint Luff, and Henry Andrews for their work on the initial drafts of JSON Schema.
Thanks to Jason Desrosiers, Daniel Perrett, Erik Wilde, Evgeny Poberezkin, Brad Bowman, Gowry Sankar, Donald Pipowitch, Dave Finlay, Denis Laxalde, Phil Sturgeon, Shawn Silverman, and Karen Etheridge for their submissions and patches to the document.
[Appendix] ChangeLog6
- draft-next
- Use IRIs instead of URIs
- Move "minContains" and "maxContains" to the applicator vocabulary (see also that changelog)
- Remove the optional automatic second-pass validation of "content*" keywords
- Clarify that "contentSchema"'s value is a schema just like any other subschema
- draft-bhutton-json-schema-validation-01
- Improve and clarify the
minContainskeyword explanation - Remove the use of "production" in favour of "ABNF rule"
- Improve and clarify the
- draft-bhutton-json-schema-validation-00
- Correct email format RFC reference to 5321 instead of 5322
- Clarified the set and meaning of
contentEncodingvalues - Reference ECMA-262, 11th edition for regular expression support
- Split
formatinto an annotation only vocabulary and an assertion vocabulary - Clarify
deprecatedwhen applicable to arrays
- draft-handrews-json-schema-validation-02
- Grouped keywords into formal vocabularies
- Update
formatimplementation requirements in terms of vocabularies - By default,
formatMUST NOT be validated, although validation can be enabled - A vocabulary declaration can be used to require
formatvalidation - Moved
definitionsto the core spec as$defs - Moved applicator keywords to the core spec
- Renamed the array form of
dependenciestodependentRequired, moved the schema form to the core spec - Specified all
content*keywords as annotations, not assertions - Added
contentSchemato allow applying a schema to a string-encoded document - Also allow RFC 4648 encodings in
contentEncoding - Added
minContainsandmaxContains - Update RFC reference for nhostname" and "idn-hostname"
- Add "uuid" and "duration" formats
- draft-handrews-json-schema-validation-01
- This draft is purely a clarification with no functional changes
- Provided the general principle behind ignoring annotations under
notand similar cases - Clarified
if/then/elsevalidation interactions - Clarified
if/then/elsebehavior for annotation - Minor formatting and cross-referencing improvements
- draft-handrews-json-schema-validation-00
- Added
if/then/else - Classify keywords as assertions or annotations per the core spec
- Warn of possibly removing
dependenciesin the future - Grouped validation keywords into sub-sections for readability
- Moved
readOnlyfrom hyper-schema to validation meta-data - Added
writeOnly - Added string-encoded media section, with former hyper-schema
mediakeywords - Restored "regex" format (removal was unintentional)
- Added "date" and "time" formats, and reserved additional RFC 3339 format names
- I18N formats: "iri", "iri-reference", "idn-hostname", "idn-email"
- Clarify that "json-pointer" format means string encoding, not URI fragment
- Fixed typo that inverted the meaning of
minimumandexclusiveMinimum - Move format syntax references into Normative References
- JSON is a normative requirement
- Added
- draft-wright-json-schema-validation-01
- Standardized on hyphenated format names with full words ("uriref" becomes "uri-reference")
- Add the formats "uri-template" and "json-pointer"
- Changed
exclusiveMaximum/exclusiveMinimumfrom boolean modifiers ofmaximum/minimumto independent numeric fields. - Split the additionalItems/items into two sections
- Reworked properties/patternProperties/additionalProperties definition
- Added
exampleskeyword - Added
containskeyword - Allow empty
requiredanddependenciesarrays - Fixed
typereference to primitive types - Added
constkeyword - Added
propertyNameskeyword
- draft-wright-json-schema-validation-00
- Added additional security considerations
- Removed reference to "latest version" meta-schema, use numbered version instead
- Rephrased many keyword definitions for brevity
- Added "uriref" format that also allows relative URI references
- draft-fge-json-schema-validation-00
- Initial draft.
- Salvaged from draft v3.
- Redefine the
requiredkeyword. - Remove
extends,disallow - Add
anyOf,allOf,oneOf,not,definitions,minProperties,maxProperties. dependenciesmember values can no longer be single strings; at least one element is required in a property dependency array.- Rename
divisibleBytomultipleOf. typearrays can no longer have schemas; removeanyas a possible value.- Rework the
formatsection; make support optional. - `format": remove attributes "phone", "style", "color"; rename "ip-address" to "ipv4"; add references for all attributes.
- Provide algorithms to calculate schema(s) for array/object instances.
- Add interoperability considerations.
| Author | Company | URI | |
|---|---|---|---|
| Austin Wright (editor) | aaa@bzfx.net | ||
| Ben Hutton (editor) | Postman | ben@jsonschema.dev | https://jsonschema.dev |
Footnotes
-
Note that the
typekeyword in this specification defines an "integer" type which is not part of the data model. Therefore a format attribute can be limited to numbers, but not specifically to integers. However, a numeric format can be used alongside thetypekeyword with a value of "integer", or could be explicitly defined to always pass if the number is not an integer, which produces essentially the same behavior as only applying to integers. ↩ -
Specifying the Format-Annotation vocabulary and enabling validation in an implementation should not be viewed as being equivalent to specifying the Format-Assertion vocabulary since implementations are not required to provide full validation support when the Format-Assertion vocabulary is not specified. ↩
-
This matches the current reality of implementations, which provide widely varying levels of validation, including no validation at all, for some or all format attributes. It is also designed to encourage relying only on the annotation behavior and performing semantic validation in the application, which is the recommended best practice. ↩
-
The expectation is that for simple formats such as date-time, syntactic validation will be thorough. For a complex format such as email addresses, which are the amalgamation of various standards and numerous adjustments over time, with obscure and/or obsolete rules that may or may not be restricted by other applications making use of the value, a minimal validation is sufficient. For example, an instance string that does not contain an "@" is clearly not a valid email address, and an "email" or "hostname" containing characters outside of 7-bit ASCII is likewise clearly invalid. ↩
-
There is not currently consensus on the need for supporting all RFC 3339 formats, so this approach of reserving the namespace will encourage experimentation without committing to the entire set. Either the format implementation requirements will become more flexible in general, or these will likely either be promoted to fully specified attributes or dropped. ↩
-
This section to be removed before leaving Internet-Draft status. ↩