Locust vs Selenium

Locust is an open-source performance and load testing tool for HTTP and other protocols. Test scenarios are written in Python, with regular Python libraries available for use within them. Tests can run from the command line or web interface, which displays throughput, response times, and errors in real time; results can be exported for later analysis. The interface shows progress and lets users change load during a run. Locust can distribute tests across multiple machines and says it can support hundreds of thousands of concurrent users. Other systems and protocols can be tested by adding a client, and documentation lists community extensions for protocols and reporting. Optional OpenTelemetry support exports traces, metrics, and logs to compatible backends such as OTLP, Prometheus, Jaeger, and Tempo. Automatic instrumentation currently covers the requests library. Installation is documented with pip install locust or uvx. Locust is free and MIT-licensed. Its documentation also describes hosted load testing through Azure Load Testing, with reporting, Application Insights integration, and CI/CD support for Azure DevOps and GitHub Actions.

Selenium is a free suite of tools for automating web browsers, primarily to test web applications. WebDriver provides language bindings for controlling browsers locally or remotely, and is a W3C Recommendation. The main project supports.NET/C#, Ruby, Java, Python, and JavaScript. Selenium IDE is a browser add-on for recording and replaying interactions in Chrome, Firefox, and Edge. For distributed tests, Selenium Grid spreads work across machines and combinations of browsers and operating systems. Grid offers Standalone, Hub and Node, and Distributed configurations; Docker and Kubernetes deployment resources are also linked. Selenium Manager can discover, download, and cache browser releases and drivers. Documentation covers browser-specific functionality for Chrome, Edge, Firefox, Internet Explorer, and Safari, and names GitHub Actions and Jenkins as CI/CD examples. Selenium began in 2004 at ThoughtWorks in Chicago. Grid has no authentication by default, and the project advises restricting external access and placing it behind a secure network. The latest Opera driver functionality is not supported, and that driver is officially unsupported. Selenium costs nothing.