bson

BSON, short for Binary JSON, is a binary-encoded serialization format for representing JSON-like documents. It is designed to be lightweight, traversable, and efficient for encoding and decoding by machines while remaining suitable for data interchange. BSON is widely used in MongoDB as the primary storage and wire protocol format, and it is also employed by various drivers and tools for transferring data between applications.

BSON documents are encoded as a sequence of elements within a length-prefixed container. Each element consists of a one-byte type, a null-terminated field name, and a value whose encoding depends on the type. The document ends with a terminating null byte. In addition to the standard JSON types (strings, numbers, booleans, null, arrays, and objects), BSON supports a richer set of types, including 32-bit and 64-bit integers, floating-point numbers, decimal128, date/time, binary data, ObjectId, regular expressions, JavaScript code, and more. Arrays and subdocuments are encoded as nested BSON documents, preserving field order.

BSON’s design emphasizes compactness and fast parsing, with little-endian encoding for numeric types and length-prefixed structures to simplify streaming parsing. It offers advantages over plain JSON in terms of type richness, data size, and performance in machine processing, but is not intended to be human-readable. While MongoDB is the most prominent user, BSON is used in other contexts as a data interchange format and internal wire protocol for distributed systems.