While the original was heavily dependent on the server to inject JavaScript into browsers, modern Selenium Server (integrated into Selenium 4) focuses on orchestrating distributed test execution using the W3C WebDriver Protocol . Core Components and Architecture
| Metric | Value/Note | |--------|-------------| | | Default 1 per browser type (configurable) | | Protocol overhead | ~5-10ms per command over localhost; higher over network | | Scalability limit | ~100-200 nodes per hub in Selenium 3; Selenium 4 improves with event bus | | Browser launch time | Adds 1-3 seconds vs direct WebDriver | selenium server
Selenium Server simplifies the management of browser binaries and versions. While the original was heavily dependent on the
| Tool | Protocol | Use Case | |------|----------|----------| | | W3C WebDriver | General cross-browser, on-prem grid | | Selenoid | Docker-native | Lightweight, high-density container grid | | BrowserStack/Sauce Labs | Cloud API | No infrastructure management | | Playwright | CDP | Fast, modern web apps (no server needed for parallel) | | Cypress | Network proxy | Component & E2E testing (not designed for Selenium Server) | While it is not required for simple local
# Check grid status curl http://localhost:4444/status
is a standalone Java application that acts as an intermediary between your test scripts (client) and the web browser drivers. While it is not required for simple local scripts, it is essential for remote execution and scaling.
