Apache JMeter

Apache JMeter is an open-source Java desktop application designed to load test functional behavior and measure performance of web applications, APIs, databases, and other services. Originally developed by Stefano Mazzocchi in 1998, JMeter has been an Apache Software Foundation project since 2001 and remains one of the most widely used load testing tools with a market presence spanning over two decades. Key features include: a GUI-based test plan builder using a tree structure of elements (Thread Groups defining virtual users and ramp-up patterns, Samplers generating requests to target systems, Configuration Elements for defaults and variables, Logic Controllers for conditional execution and looping, Timers for pacing between requests, Assertions for validating responses, Pre-Processors and Post-Processors for request preparation and response extraction, and Listeners for result collection and visualization), support for numerous protocol samplers including HTTP/HTTPS (web applications and REST APIs), JDBC (database queries), FTP, SMTP/POP3/IMAP (email), TCP, LDAP, SOAP, JMS, MongoDB, and JUnit, JSR223 scripting (Groovy, JavaScript, Beanshell, and other JVM languages for custom request manipulation and response processing), parameterization via CSV files (feeding different test data to virtual users for realistic load simulation), correlation (extracting dynamic values like session tokens from responses and using them in subsequent requests via Regular Expression Extractor, JSON Path Extractor, XPath Extractor, or CSS Selector Extractor), distributed testing (master-slave architecture for generating load from multiple machines), real-time results via Backend Listener (sending metrics to InfluxDB or Graphite for live dashboards in Grafana), HTML report generation with charts (response times, throughput, errors, percentiles), and plugin ecosystem via JMeter Plugins Manager. JMeter is written in Java and licensed under Apache-2.0.