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MongoDB Extended JSON (v2)

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Disambiguation

The following page discusses MongoDB Extended JSON v2. For discussion on the Legacy MongoDB Extended JSON v1, see MongoDB Extended JSON (v1).

For mongo shell wrapper methods for types, see Data Types in the mongo Shell.

JSON can only directly represent a subset of the types supported by BSON. To preserve type information, MongoDB adds the following extensions to the JSON format.

  • Canonical Mode
    A string format that emphasizes type preservation at the expense of readability and interoperability. That is, conversion from canonical to BSON will generally preserve type information except in certain specific cases.
  • Relaxed Mode
    A string format that emphasizes readability and interoperability at the expense of type preservation. That is, conversion from relaxed format to BSON can lose type information.

Both formats conform to the JSON RFC and can be parsed by the various MongoDB drivers and tools.

MongoDB Extended JSON v2 Usage

Drivers

The following drivers use the Extended JSON v2.0

  • C
  • C++
  • Go
  • Java
  • Node
  • Perl
  • PHPC
  • Python
  • Scala

For C# and Ruby that use Legacy MongoDB Extended JSON v1, refer to MongoDB Extended JSON (v1).

MongoDB Command-Line Tools

Starting in version 4.2:

bsondump Uses Extended JSON v2.0 (Canonical mode) format.
mongodump

Use Extended JSON v2.0 (Canonical mode) format for the metadata. Requires mongorestore version 4.2+ that supports Extended JSON v2.0 (Canonical mode or Relaxed) format.

Tip

In general, use corresponding versions of mongodump and mongorestore. That is, to restore data files created with a specific version of mongodump, use the corresponding version of mongorestore.
mongoexport
Creates output data in Extended JSON v2.0 (Relaxed mode) by default.
Creates output data in Extended JSON v2.0 (Canonical mode) if used with --jsonFormat.
mongoimport
Expects import data to be in Extended JSON v2.0 (either Relaxed or Canonical mode) by default.
Can recognize data that is in Extended JSON v1.0 format if the option --legacy is specified.

Tip

In general, the versions of mongoexport and mongoimport should match. That is, to import data created from mongoexport, you should use the corresponding version of mongoimport.

BSON Data Types and Associated Representations

The following presents some common BSON data types and the associated representations in Canonical and Relaxed.

For a complete list, see https://github.com/mongodb/specifications/blob/master/source/extended-json.rst#conversion-table.

Array
Canonical Relaxed 
[ <elements> ]

<Same as Canonical>
Where the array elements are as follows:
  • <elements>
    Array elements use Extended JSON. To specify an empty array, omit the content [ ].
Binary
Canonical Relaxed 
{ "$binary":
   {
      "base64": "<payload>",
      "subType": "<t>"
   }
}

<Same as Canonical>
Where the values are as follows:
  • "<payload>"
    Base64 encoded (with padding as “=”) payload string.
  • "<t>"
    A one- or two-character hex string that corresponds to a BSON binary subtype. See the extended bson documentation http://bsonspec.org/spec.html for subtypes available.
Date

For dates between years 1970 and 9999, inclusive:

Canonical Relaxed 
{"$date": {"$numberLong": "<millis>"}}

{"$date": "<ISO-8601 Date/Time Format>"}

For dates before year 1970 or after year 9999:

Canonical Relaxed 
{"$date": {"$numberLong": "<millis>"}}

<Same as Canonical>
Where the values are as follows:
  • "<millis>"
    A 64-bit signed integer as string. The value represents milliseconds relative to the epoch.
  • "<ISO-8601 Date/Time Format>"
    A date in ISO-8601 Internet Date/Time Format as string. The date/time has a maximum time precision of milliseconds:
    • Fractional seconds have exactly 3 decimal places if the fractional part is non-zero.
    • Otherwise, fractional seconds SHOULD be omitted if zero.
Decimal128

New in version 3.4.

Canonical Relaxed 
{ "$numberDecimal": "<number>" }

<Same as Canonical>
Where the values are as follows:
Document
Canonical Relaxed 
{ <content> }

<Same as Canonical>
Where the document contents are as follows:
  • <content>
    Name:value pairs that use Extended JSON. To specify an empty document, omit the content { }.
Double

For finite numbers:

Canonical Relaxed 
{"$numberDouble": "<decimal string>" }

<non-integer number>

For infinite numbers or NAN:

Canonical Relaxed 
{"$numberDouble": <"Infinity"|"-Infinity"|"NaN"> }

<Same as Canonical>
Where the values are as follows:
  • "<decimal string>"
    A 64-bit signed floating point as a string.
  • <non-integer number>
    A non-integer number. Integer numbers are parsed as integer instead of double.
Int64
Canonical Relaxed 
{ "$numberLong": "<number>" }

<integer>
Where the values are as follows:
  • "<number>"
    A 64-bit signed integer as string.
  • <integer>
    A 64-bit signed integer.
Int32
Canonical Relaxed 
{ "$numberInt": "<number>" }

<integer>
Where the values are as follows:
  • "<number>"
    A 32-bit signed integer as string.
  • <integer>
    A 32-bit signed integer.
MaxKey
Canonical Relaxed 
{ "$maxKey": 1 }

<Same as Canonical>

The MaxKey BSON data type compares higher than all other types. See Comparison/Sort Order for more information on comparison order for BSON types.

MinKey
Canonical Relaxed 
{ "$minKey": 1 }

<Same as Canonical>

The MinKey BSON data type compares lower than all other types. See Comparison/Sort Order for more information on comparison order for BSON types.

ObjectId
Canonical Relaxed 
{ "$oid": "<ObjectId bytes>" }

<Same as Canonical>
Where the values are as follows:
  • "<ObjectId bytes>"
    A 24-character, big-endian hexadecimal string that represents the ObjectId bytes.
Regular Expression
Canonical Relaxed 
{ "$regularExpression":
   {
      "pattern": "<regexPattern>",
      "options": "<options>"
  }
}

<Same as Canonical>
Where the values are as follows:
  • "<regexPattern>"

    A string that corresponds to the regular expression pattern. The string can contain valid JSON characters and unescaped double quote (") characters, but may not contain unescaped forward slash (/) characters.

  • "<options>"

    A string that specifies BSON regular expression options (‘g’, ‘i’, ‘m’ and ‘s’) or an empty string "".

    Options other than (‘g’, ‘i’, ‘m’ and ‘s’) will be dropped when converting to this representation.

    Important

    The options MUST be in alphabetical order.
Timestamp
Canonical Relaxed 
{"$timestamp": {"t": <t>, "i": <i>}}

<Same as Canonical>
Where the values are as follows:
  • <t>
    A positive integer for the seconds since epoch.
  • <i>
    A positive integer for the increment.

Example

Example Field Name Canonical Format Relaxed Format
“_id:” {“$oid”:”5d505646cf6d4fe581014ab2”} {“$oid”:”5d505646cf6d4fe581014ab2”}
“arrayField”: [“hello”,{“$numberInt”:”10”}] [“hello”,10]
“dateField”: {“$date”:{“$numberLong”:”1565546054692”}} {“$date”:”2019-08-11T17:54:14.692Z”}
“dateBefore1970”: {“$date”:{“$numberLong”:”-1577923200000”}} {“$date”:{“$numberLong”:”-1577923200000”}}
“decimal128Field”: {“$numberDecimal”:”10.99”} {“$numberDecimal”:”10.99”}
“documentField”: {“a”:”hello”} {“a”:”hello”}
“doubleField”: {“$numberDouble”:”10.5”} 10.5
“infiniteNumber” {“$numberDouble”:”Infinity”} {“$numberDouble”:”Infinity”}
“int32field”: {“$numberInt”:”10”} 10
“int64Field”: {“$numberLong”:”50”} 50
“minKeyField”: {“$minKey”:1} {“$minKey”:1}
“maxKeyField”: {“$maxKey”:1} {“$maxKey”:1}
“regexField”: {“$regularExpression”:{“pattern”:”^H”,”options”:”i”}} {“$regularExpression”:{“pattern”:”^H”,”options”:”i”}}
“timestampField”: {“$timestamp”:{“t”:1565545664,”i”:1}} {“$timestamp”:{“t”:1565545664,”i”:1}}

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