μpb (often written 'upb') is a small protobuf implementation written in C.

upb is the core runtime for protobuf languages extensions in Ruby, PHP, and Python.

While upb offers a C API, the C API & ABI are not stable. For this reason, upb is not generally offered as a C library for direct consumption, and there are no releases.

upb has comparable speed to protobuf C++, but is an order of magnitude smaller in code size.

Like the main protobuf implementation in C++, it supports:

• a generated API (in C)
• reflection
• binary & JSON wire formats
• text format serialization
• all standard features of protobufs (oneofs, maps, unknown fields, extensions, etc.)
• full conformance with the protobuf conformance tests

upb also supports some features that C++ does not:

• optional reflection: generated messages are agnostic to whether reflection will be linked in or not.
• no global state: no pre-main registration or other global state.
• fast reflection-based parsing: messages loaded at runtime parse just as fast as compiled-in messages.

However there are a few features it does not support:

• text format parsing
• deep descriptor verification: upb's descriptor validation is not as exhaustive as protoc.

For Ruby, use RubyGems:

$ gem install google-protobuf

For PHP, use PECL:

$ sudo pecl install protobuf

For Python, use PyPI:

$ sudo pip install protobuf

Alternatively, you can build and install upb using vcpkg dependency manager:

git clone https://github.com/Microsoft/vcpkg.git
cd vcpkg
./bootstrap-vcpkg.sh
./vcpkg integrate install
./vcpkg install upb

The upb port in vcpkg is kept up to date by microsoft team members and community contributors.

If the version is out of date, please create an issue or pull request on the vcpkg repository.

Please see CONTRIBUTING.md.