Commands are key combinations that invoke an extension feature. Register commands
in the manifest under the `"commands"` key. For example:

    {
      "name": "Open developer.chrome.com",
      "version": "0.1",
      "manifest_version": 3,
      "description": "Opens developer.chrome.com when you use Cmd/Ctrl + Shift + Z",
      "background": {
        "service_worker": "background.js"
      },
      "commands": {
       "open-tab": {
         "suggested_key": {
           "default": "Ctrl+Shift+Z",
           "mac": "Command+Shift+Z"
         },
         "description": "Open developer.browser.com"
       }
      }
    }

This key combination triggers the
[`commands.onCommand`](https://developer.chrome.com/docs/extensions/reference/api/commands#event-onCommand)
event in the
[service worker](https://developer.chrome.com/docs/extensions/develop/concepts/service-workers/basics).

    browser.commands.onCommand.addListener((command) => {
      if (command !== "open-tab") return;
      browser.tabs.create({ url: "https://developer.chrome.com" });
    });

To see responding to commands in action, download the
[Tab Flipper](https://github.com/GoogleChrome/chrome-extensions-samples/tree/main/api-samples/default_command_override) sample and [load it unpacked](https://developer.chrome.com/docs/extensions/get-started/tutorial/hello-world#load-unpacked).