Build Matrix is an innovative feature introduced by Buildkite that allows users to create multiple job variants from a single step definition, simplifying complex and repetitive pipelines. By leveraging the {{matrix}} variable, users can expand a single step into multiple steps across different operating systems and architectures, such as macOS, Linux, and Windows, all within a unified framework. This approach minimizes boilerplate code and reduces pipeline management time, as demonstrated by a recent update to the Buildkite agent repository that significantly decreased the number of lines in a pipeline. Build Matrix also supports advanced features for power users, such as adding multiple dimensions and using the adjustments key to define all matrix elements, as well as grouping jobs for better clarity. The feature is now available to all Buildkite customers, with additional documentation provided for further guidance.