BSON (/ˈbiːsən/; 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 {"hello": "world"} will be stored as:

See also

External links