Firefox Network Diagnostics: HTTP/3, DNS, and WebSockets

This article provides a quick overview of the live network diagnostics available on the about:networking page in the Firefox Web Browser. It specifically covers how to monitor and analyze real-time data for HTTP/3 connections, DNS cache entries, and WebSocket communications directly from the browser without needing external packet-sniffing tools.

To view these diagnostics, type about:networking into the Firefox address bar and press Enter. For live monitoring, check the "Autorefresh every 3 seconds" box in the top right corner of the interface.

HTTP/3 Connections

Located under the HTTP tab, Firefox displays a table of all active and idle HTTP connections. Because HTTP/3 runs over the QUIC protocol rather than standard TCP, monitoring it here confirms whether sites are successfully negotiating the newer protocol. You can monitor the following live diagnostics:

  • Host: The domain name of the server the browser is communicating with.
  • Port: The network port used for the connection (typically port 443).
  • HTTP Version: Explicitly identifies the protocol in use, allowing you to filter and confirm active HTTP/3 sessions alongside older HTTP/1.1 and HTTP/2 traffic.
  • SSL: A boolean indicator (true/false) confirming encryption. For HTTP/3, this will always read as true.
  • Active and Idle: Live counters showing the exact number of currently active data streams versus idle connections being kept alive for that specific host.

DNS Cache Entries

Located under the DNS tab, Firefox reveals its internal Domain Name System cache. This section is vital for troubleshooting name resolution issues and verifying privacy settings. The live metrics include:

  • Hostname: The specific web domain that has been resolved.
  • Family: Indicates the IP protocol version used for the resolution, displayed as either ipv4 or ipv6.
  • TRR (Trusted Recursive Resolver): A true/false value indicating whether the DNS query was routed securely through DNS over HTTPS (DoH) rather than the local network's default DNS server.
  • Addresses: The actual resolved IP address (or multiple addresses) associated with the hostname.
  • Expires (Seconds): A live countdown timer showing how many seconds remain before the cached entry expires and requires a fresh lookup.

This tab also features a "Clear DNS Cache" button, which immediately purges all entries listed in the table to force fresh resolutions.

WebSockets

Located under the WebSockets tab, Firefox tracks persistent, bi-directional communication channels often used for live chats, gaming, and real-time data feeds. Unlike standard HTTP requests, these connections stay open to pass data back and forth continuously. You can monitor the following diagnostics:

  • Hostname: The destination URL of the WebSocket server.
  • SSL: Indicates whether the WebSocket is using an encrypted connection (wss://) or an unencrypted connection (ws://).
  • Messages Sent: A live counter tracking the total number of individual data frames the browser has pushed to the server.
  • Messages Received: A live counter tracking the total number of data frames the server has pushed to the browser.
  • Bytes Sent: The cumulative size of all outbound data transmitted over that specific WebSocket connection.
  • Bytes Received: The cumulative size of all inbound data received from the server, which is useful for identifying memory leaks or bandwidth-heavy web applications.