A Ninja Build System Configuration File, often named build.ninja, is a low-level build script used by the Ninja build system. Ninja is an open-source build system designed for speed, focusing on incremental builds. Unlike higher-level build systems like Make or CMake, Ninja files are not typically written by hand. Instead, they are usually generated by a 'meta-build system' such as CMake, Meson, or GYP, which translates a more abstract project description into the highly optimized, parallelizable build instructions that Ninja can execute. These files contain a directed acyclic graph (DAG) of build steps, specifying inputs, outputs, and commands for each step. The primary goal of Ninja is to execute these build steps as quickly as possible, making it particularly popular for large C++ projects where build times can be a significant bottleneck. The .ninja extension itself is not strictly standardized for all files, but build.ninja is the canonical name for the main build script.