Supported UI Elements

Descriptions and examples of MailExtension APIs to interact with Thunderbird's user interface.

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.

If the action button is defined as a menu typed action button, it will open a drop-down menu when clicked.

Note: The browserAction API has been renamed to action in Manifest V3.

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.

If the action button is defined as a menu typed action button, it will open a drop-down menu when clicked.

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.

If the action button is defined as a menu typed action button, it will open a drop-down menu when clicked.

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:

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. Examples can be found in our example repository.

Thunderbird menus are accessible through the following context types:

ContextDescription

all

Add menu entries to all supported contexts, excluding tab and tools_menu.

all_message_attachments

action, browser_action, compose_action , message_display_action Note: browser_action is available in Manifest V2 and action is available in Manifest V3.

action_menu, browser_action_menu, compose_action_menu, message_display_action_menu, Note: browser_action_menu is available in Manifest V2 and action_menu is available in Manifest V3.

Add entries to the drop-down menu of menu typed action buttons.

compose_attachments

editable, password

Add entries to the context menu of text/password input fields in WebExtension windows, web tabs or message display tabs.

folder_pane

image, audio, video

link

Add entries to the context menu of links in WebExtension windows, in web tabs or in message display tabs.

message_attachments

message_list

page, frame

Add entries to the context menu of WebExtension windows, web tabs or message display tabs, if none of the other content contexts apply (link, selection, image, audio, video, editable, password).

selection

Add entries to the context menu in WebExtension windows, web tabs or message display tabs, if any text has been selected.

tab

The tab context can also be used to override the context menu of content pages (action popups or content tabs).

See the menu example for more details.

tools_menu

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