Files
json/docs/mkdocs/docs/features/binary_formats/index.md
T
Niels Lohmann 52b72b5684 Improve documentation: byte layouts, release pages, See also, dark-mode images (#5906)
- Make the iterator range illustrations legible in dark mode (prefers-color-scheme
  rules inside the SVGs).
- Add a "Byte layout" section with a color-coded byte table to each binary format
  page (BJData, BON8, BSON, CBOR, MessagePack, UBJSON), and highlight the smallest
  size per file in the comparison table.
- Add "See also" sections to the overview pages that lacked one.
- Split the release notes into one page per release, grouped by minor version on
  the overview page, with an "API changes" section per release generated from the
  API pages' version histories (hooks/api_changes.py).
- Fact-check the release notes and version histories against the release tags and
  correct wrong or misleading entries (e.g., json_serializer 2.1.0, merge_patch
  3.1.0, items, count, operator[], to_bjdata, std::string_view key support).

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
2026-10-24 17:57:44 +02:00

3.9 KiB

Binary Formats

Though JSON is a ubiquitous data format, it is not a very compact format suitable for data exchange, for instance, over a network. Hence, the library supports

to efficiently encode JSON values to byte vectors and to decode such vectors.

Comparison

Completeness

Format Serialization Deserialization
BJData complete complete
BON8 incomplete: no unsigned integers above int64 complete
BSON incomplete: top-level value must be an object incomplete, but all JSON types are supported
CBOR complete incomplete, but all JSON types are supported
MessagePack complete complete
UBJSON complete complete

Binary values

Format Binary values Binary subtypes
BJData not supported not supported
BON8 not supported not supported
BSON supported supported
CBOR supported supported
MessagePack supported supported
UBJSON not supported not supported

See binary values for more information.

Sizes

Format canada.json twitter.json citm_catalog.json jeopardy.json
BJData 53.2 % 91.1 % 78.1 % 96.6 %
BJData (size) 58.6 % 92.1 % 86.7 % 97.4 %
BJData (size+type) 58.6 % 92.1 % 86.5 % 97.4 %
BON8 50.5 % 83.8 % 63.5 % 87.5 %
BSON 85.8 % 95.2 % 95.8 % 106.7 %
CBOR 50.5 % 86.3 % 68.4 % 88.0 %
MessagePack 50.5 % 86.0 % 68.5 % 87.9 %
UBJSON 53.2 % 91.3 % 78.2 % 96.6 %
UBJSON (size) 58.6 % 92.3 % 86.8 % 97.4 %
UBJSON (size+type) 55.9 % 92.3 % 85.0 % 95.0 %

Sizes compared to minified JSON value; the smallest size per file is printed in bold.

See also