Network Monitor

The Network Monitor (netmonitor) shows you all the network requests Firefox makes (for example, when a page is loaded or when an XMLHttpRequest is performed) , how long each request takes, and details of each request. You can edit the method, query, header and resend the request as well. Read more to learn all the features and how to use the tool.


The Network Monitor UI is built using React components (in src/components/).

  • MonitorPanel in MonitorPanel.js is the root element.

  • Three major container components are

    • Toolbar Panel related functions.

    • RequestList Show each request information.

    • NetworkDetailsBar Show detailed information per request.

    • StatusBar Show statistics while loading.

  • src/assets Styles that affect the Network Monitor panel.

We prefer stateless component (define by function) instead of stateful component (define by class) unless the component has to maintain its internal state.


Besides the UI, the Network Monitor manages the app state via Redux. The following locations define the app state:

  • src/constants.js constants used across the tool including action and event names.

  • src/actions/ for all actions that change the state.

  • src/reducers/ for all reducers that change the state.

  • src/selectors/ functions that return a formatted version of parts of the app state.

We use reselect library to perform state calculations efficiently.