Selenium BiDi Protocol Event Listener Browser Version Requirements

Minimum Browser Version Requirements

Stable registration of BiDi event listeners, such as network.beforeRequestSent, depends on the browser's implementation of the WebDriver BiDi specification. Because this protocol is evolving, support is not uniform across stable releases.

• Chromium-based (Chrome, Edge): Generally requires the latest stable versions (typically v115+), as these browsers leverage the Chrome DevTools Protocol (CDP) as a foundation for BiDi. For the most stable experience with network interception, using the latest stable build is recommended.
• Firefox: Full BiDi support often lags behind the stable release cycle. Stable versions may have partial support, but for comprehensive event listener registration, Firefox Nightly or Beta builds are frequently required.

Session Configuration and Stability

BiDi listeners operate over a WebSocket connection established during session creation, which is distinct from the standard HTTP-based WebDriver API. To ensure consistent behavior and avoid WebSocket instability during long-running sessions, consider the following:

Required Configuration Approaches

1. BiDi-Enabled Capabilities: Ensure your driver capabilities explicitly enable BiDi. While often automatic in newer Selenium 4.x versions, verifying that the webSocketUrl is correctly negotiated during the handshake is critical.
2. Synchronization Management: When mixing traditional WebDriver commands (like findElement) with BiDi listeners, you must manually handle synchronization. BiDi events are asynchronous; the driver does not automatically wait for a BiDi event to trigger before executing the next WebDriver command.
3. WebSocket Keep-Alive: To prevent timeouts in long-running sessions, ensure your network infrastructure (proxies/firewalls) does not terminate idle WebSocket connections, as the BiDi protocol relies on this persistent pipe for real-time event delivery.

Verification Steps

To verify if your current environment supports BiDi event listeners, execute a scoped test for console log monitoring:

# Example logic for verification
# 1. Initialize driver with BiDi capabilities
# 2. Register a listener for 'console.close' or 'log'
# 3. Trigger a console.log() in the browser
# 4. Confirm the event is received via the WebSocket callback

Assumptions and Uncertainties

This guidance assumes the use of Selenium 4.x. Because the WebDriver BiDi protocol is an active W3C standard, specific version numbers for "stability" shift frequently. There is currently no single, static version number that guarantees 100% parity across all vendors for every BiDi event.

Diagnostic Detail Needed: Are you utilizing a remote Selenium Grid or a local driver instance? This significantly changes the recommendation regarding WebSocket proxy configurations and session-level flags.