ApacheBench (ab) is a command-line benchmarking tool designed to measure the performance of web servers, initially for Apache but applicable to any HTTP server. It evaluates server capabilities by sending a high volume of HTTP requests and recording metrics such as request latency and success rates. The tool allows users to configure parameters like the number of requests, timeout limits, and request headers, providing output in the form of detailed reports. These reports include metrics on request latency, connection times, and success rates, helping users identify areas for optimization in server performance. ApacheBench operates on a single thread and has certain constraints, such as requiring sufficient CPU and memory resources on the testing host and potentially not reflecting real-world request handling due to its send-everything-at-once approach. Despite its limitations, ApacheBench is useful for assessing server efficiency and optimizing server configurations, with its metrics offering insights into latency distribution and response success rates.