BSON

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Computer data interchange format

title: "BSON" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["json", "data-serialization-formats", "document-oriented-databases"] description: "Computer data interchange format" topic_path: "technology/databases" source: "https://en.wikipedia.org/wiki/BSON" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Computer data interchange format ::

::data[format=table title="Infobox file format"]

Field	Value
screenshot	BSON website logo.svg
name	BSON
_nomimecode	on
mime
extension	.bson
genre	Data interchange
extended from	JSON
url
::

BSON (; Binary JSON) is a computer data interchange format extending JSON. It is a binary form for representing simple or complex data structures including associative arrays (also known as name-value pairs), integer indexed arrays, and a suite of fundamental scalar types. BSON originated in 2009 at MongoDB. Several scalar data types are of specific interest to MongoDB and the format is used both as a data storage and network transfer format for the MongoDB database, but it can be used independently outside of MongoDB. Implementations are available in a variety of languages such as C, C++, C#, D, Delphi, Erlang, Go, Haskell, Java, JavaScript, Julia, Lua, OCaml, Perl, PHP, Python, Ruby, Rust, Scala, Smalltalk, and Swift.

Data types and syntax

BSON has a published specification. The topmost element in the structure must be of type BSON object and contains 1 or more elements, where an element consists of a field name, a type, and a value. Field names are strings. Types include:

Unicode string (using the UTF-8 encoding)
32-bit integer
64-bit integer
double (64-bit IEEE 754 floating point number, including NaN/Inf)
decimal128 (128-bit IEEE 754-2008 floating point number; binary integer decimal (BID) variant), suitable as a carrier for decimal-place sensitive financial data and arbitrary precision numerics with 34 decimal digits of precision, a max value of approximately 106145
datetime in UTC (signed 64-bit integer number of milliseconds since the Unix epoch)
byte array (for arbitrary binary data)
Boolean (true and false)
null
BSON object
BSON array
JavaScript code
MD5 binary data
Regular expression (Perl compatible regular expressions ("PCRE") version 8.41 with UTF-8 support)

An important differentiator to JSON is that BSON contains types not present in JSON (e.g. datetime, byte array, and proper IEEE 754 floats) and offers type-strict handling for several numeric types instead of a universal "number" type. For situations where these additional types need to be represented in a textual way, MongoDB's Extended JSON format can be used.

Efficiency

Compared to JSON, BSON is designed to be efficient both in storage space and scan-speed. Large elements in a BSON document are prefixed with a length field to facilitate scanning. In some cases, BSON will use more space than JSON due to the length prefixes and explicit array indices.

Example

A document such as will be stored as:

::code[lang=json] \x16\x00\x00\x00 // total document size \x02 // 0x02 = type String hello\x00 // field name \x06\x00\x00\x00world\x00 // field value (size of value, value, null terminator) \x00 // 0x00 = type EOO ('end of object') ::

References

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::