Browser Action

A browser action adds a button to Thunderbird's main toolbar:

It is controlled by the browser_action manifest key in the extension's manifest.json file:

"browser_action": {
    "default_title": "Restart",
    "default_icon" : "restart.png",
    "default_popup": "browser_popup.html"
}, 

If a default_popup is defined, a popup will be opened and the defined html page will be loaded, when the button is clicked. Additionally, you can use the browserAction API in your background script to interact with the button to modify badge text, icon, title or its enabled state.

Compose Action

A compose action adds a button to the toolbar of the composer window:

It is controlled by compose_action manifest key in the extension's manifest.json file:

"compose_action": {
    "default_title": "Expand lists",
    "default_icon" : "lists.png",
    "default_popup": "compose_popup.html"
}, 

If a default_popup is defined, a popup will be opened and the defined html page will be loaded, when the button is clicked. Additionally, you can use the composeAction API in your background script to interact with the button to modify badge text, icon, title or its enabled state.

Message Display Action

A message display action adds a button to the toolbar of the message view window:

It is controlled by the message_display_action manifest key in the extension's manifest.json file:

"message_display_action": {
    "default_title": "Copy Patch",
    "default_icon" : "patch.png",
    "default_popup": "message_popup.html"
	},

If a default_popup is defined, a popup will be opened and the defined html page will be loaded, when the button is clicked. Additionally, you can use the messageDisplayAction API in your background script to interact with the button to modify badge text, icon, title or its enabled state.

CloudFile Provider Configuration

Thunderbird supports cloud providers to upload large attachments to a server, instead of attaching them directly to the email. Extensions can register such cloud providers using the CloudFile API. These providers can be managed in Thunderbird's Composition options:

Menu Items

The menus API allows modifying Thunderbird's menus by adding or overriding menu items. The menu items can be added to different menus based on the provided context type. The following values are currently supported:

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