What is a Node in Selenium Grid?

Nodes are the machines that are attached to the Selenium Grid Hub and have Selenium WebDriver instances running test scripts.

Key characteristics:

• ✓Multiple nodes can be attached to one Hub
• ✓Each node can have different browsers, browser versions, or operating systems
• ✓Nodes actually execute the tests (unlike the Hub which only routes)
• ✓A single machine can run multiple node instances on different ports

Starting a Node (Selenium 4):

# Node on the same machine as hub
java -jar selenium-server-4.x.jar node --hub http://localhost:4444

# Node on a different machine
java -jar selenium-server-4.x.jar node --hub http://hub-ip:4444

Node registers its capabilities to the hub:

• ✓Browser name (Chrome, Firefox, Edge)
• ✓Browser version
• ✓Platform (Windows, Linux, macOS)
• ✓Max concurrent sessions

Typical multi-node setup:

Hub (192.168.1.100:4444)
    ├── Node 1 (192.168.1.101) → Chrome, Windows
    ├── Node 2 (192.168.1.102) → Firefox, Linux
    └── Node 3 (192.168.1.103) → Safari, macOS

Hub vs Node summary: