Load testing is a performance testing methodology used to evaluate how a software system, application, or infrastructure behaves under a specific expected load. It measures system performance, stability, and scalability when multiple users access the system concurrently or when large amounts of data are processed.

The goal of load testing is to determine whether the application can handle the anticipated user traffic or data volume without degrading performance, crashing, or causing delays. Key metrics evaluated during load testing include response time, throughput, latency, resource utilization (CPU, memory), and error rates.

Load testing tools such as Apache JMeter, LoadRunner, and Gatling simulate virtual users to generate traffic and monitor the system's response under varying levels of load. This helps identify bottlenecks, such as slow database queries, insufficient server resources, or poor application architecture, which could lead to performance degradation in real-world usage scenarios.

Load testing is essential for ensuring that applications meet Service Level Agreements (SLAs) and can handle peak usage times without negatively impacting the user experience. It is commonly performed before launching new systems or after significant updates to ensure they meet performance requirements.