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Universal Binary JSON (UBJSON) for D

A high-level library to read and write to the Universal Binary JSON (Draft 8) format using native D data types.


JSON has become a ubiquitous text-based file format for data interchange. Its simplicity, ease of processing and (relatively) rich data typing made it a natural choice for many developers needing to store or shuffle data between systems quickly and easy.

In high-performance applications, avoiding the text-processing step of JSON can net big wins in both processing time and size reduction of stored information, which is where a binary JSON format becomes helpful. The existing binary JSON specifications all define incompatibilities or complexities that undo the singular tenant that made JSON so successful: simplicity.

UBJSON for D provides absolute compatibility with the JSON spec itself as well as only utilizing data types that are natively supported by D.

Salient Features

  • Read-optimized format for high performance parsing
  • 30% lossless size reduction vs JSON, on average
  • 100% compatible with JSON
  • Binary data is readable (no compression)
  • Simple

Suggested use cases

  • An inter/intra process data exchange protocol
  • Binary RPC
  • Base level format for CouchDB ;)
  • Serialized JSON to files
  • Anywhere you would have used JSON!


To encode and decode is dead simple :

immutable(ubyte)[] ubjson = encode(int.max);
Element[] elements = decode(ubjson);

'encode' is variable-arguments template that can be called with multiple types.

immutable(ubyte)[] ubjson = encode(int.max, "Hello World!", byte.max, true, null);

Encoding to bytes is simple but not enough for idiomatic data manipulation. A better way to create and manipulate ubjson values is to use the 'elements' template

Element[] elms = elements("Hello, "World!", int.max); //2 string and an 'int' element

An Element

An 'Element' struct represents a value. This could be a static value type (ex: int, bool, string) or a container (array, object). The struct allows you to conveniently introspect, manipulate and output the value in its container. With 'Element' you can :

  • Get and compare types
  • Get the value in its native type (for static types)
  • Iterate over values (arrays)
  • Use ranges to access and append a subset of child elements (arrays)
  • Append, manipulate and remove key-value pairs as associative arrays (objects)
  • Print any value as a string
  • Output arbitrarily large objects in JSON format
  • Easily convert arbitrarily large containers to ubjson individually.

Here's how you can convert your Element to ubjson

immutable(ubyte)[] ubjson = person.bytes(); //And finally, convert it to ubjson format


An array is a sequence of items. Here are some array operations.

Element tags = arrayElement("D", "Python", "PHP", "Javascript", "C"); //Create an array of strings

assert(tags.length == 5);
writeln(tags); //["D", "Python", "PHP", "Javascript", "C"]

tags.remove(2); //Remove "PHP"
writeln(tags); //["D", "Python", "Javascript", "C"]

tags ~= elements("MySQL", "PostgreSql"); // Append tags
writeln(tags); //["D", "Python", "Javascript", "C", "MySQL", "PostgreSql"]

The arrayElement template supports all the data types used by JSON, including nested containers.

 Element data = arrayElement("A string", 123, 456.0, true, null, arrayElement("D", "Python", "PHP", "Javascript", "C"));


Objects are key-value pairs. The below code creates and queries an object.

Element person = objectElement("Name", "Adil", "Age", 29, "Score", 99.15, "Skills", tags);
writeln(person); //{Name:"Adil", "Age":29, Score:99.15, Skills:["D", "Python", "Javascript", "C"]}

//What's my name?
Element name = person["Name"];
writeln("Name : ", name); // "Name : Adil"

Modify an object's attribute

person["Name"] = "Batman"; // Assign any value that can be converted to an Element. Doesn't have to be a string
writeln("Name : ", person["Name"]); // "Name : Batman"

More examples

See example.d for more detailed samples. To run the examples :

dub run -c example

Running Unit Tests

make test

All's well that prints nothing!

UBJSON Dump Utility

This simple utility will dump a file containing ubjson. Some sample files are located in src/resources. To print a dump :

dub build -c dump
./dump examples/resources/CouchDB4k.ubj

What's missing

Streaming support. However, Draft 9 introduces changes that make streaming a natural part of the protocol. Hence streaming will not be supported until Draft 9 is out.

Contribute to this project

Please download and play with this project. Open tickets for bugs. To contribute code simply fork this repository and send a pull request. Any thoughts on how to improve the code, documentation, performance and anything else is very welcome.

Adil Baig
Blog :
Twitter : @aidezigns


Universal Binary JSON for D







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