Open source Load Testing tools comparative study
Summary
Different open-source load-testing tools report response times in very different ways, and default settings can drastically affect results. A single test scenario was executed with JMeter, Locust, Gatling, and K6 using identical load, connection reuse disabled and a shared target URL. The study shows major discrepancies across tools due to differences in TCP/TLS handling, connection pooling, DNS resolution, and timing definitions.
JMeter and Gatling report values close to browser timings, while Locust reports significantly higher numbers and K6 under-reports unless metrics are combined. Understanding how each tool measures response time is essential before comparing results or drawing performance conclusions. The key takeaway: trust results only when you know exactly what the tool is measuring and how its configuration impacts the load.