What's New
  • 2011-05-14: Initial version 1.0 released
  • 2011-06-17: v1.1
  • 2011-07-08: v1.2
  • 2011-08-24: v1.3
  • 2011-10-01: v1.4
  • 2013-01-20: v1.6
  • 2013-04-20: v1.7
  • 2015-06-30: v2.0
  • 2016-06-30: v2.3

The AttachmentCount extension allows for instantly viewing of the number of attachments in a message by adding a column to the thread pane. Text attachments may be quickly previewed. Please see Screenshots for a preview.


AttachmentCount v2.3 (Tb 45.0+)

AttachmentCount v2.0 (Tb 38.0 - Tb 44.0)

AttachmentCount v1.7 (Tb 22.0 - Tb 31.*)


Thunderbird 22.0 or higher.


AttachmentCount adds an optional column to the thread pane showing the number of attachments in a message. Use the thread pane columnpicker to select the Attachment Counts column and then drag it to whatever position you like.

The status icon of an attachment is updated automatically on an attachment detach/delete. A shift-click twice on the column header may be performed to refresh the counts/status - for messages in the visible rows only. You may also click on the column row to refresh an individual message.

Set the pref AttachmentCount.logging.console to debug or trace to see details of the mime parts of a message (on shift-click or icon click refreshes).

IMAP: In order for IMAP message attachment counts to be calculated, the message must be downloaded if it is unavailable locally. The pref downloadPrefs contains a string with download options. The defaults are to download and calculate, and as this is asynchronous there should be little delay effect even for large attachments. If this is undesired, the imapAllowDownload value may be set to false and imapPartsOnDemand value may be set to true in the pref string. Instead of counts, the generic attachment icon will be shown instead.

NNTP: The api used to get attachment counts is not available for newsgroup (NNTP) attachments, so counts aren't available.

Preview: A simple preview has been implemented for single attachments in the thread pane, without the need to select the message. Hover the icon to show a preview of approximately the first page in a tooltip. The active icon is highlighted.

Preview is available for attachments with a contentType starting with text/ or other text equivalent contentType, or starting with application/ and having several known text contenType values. Users may add custom ContentType values in the pref previewContentTypes. Attachments that cannot be previewed will display the filename and contentType only. Note that non-text or binary attachments will currently not preview, regardless of adding an unsupported contentType to the preference.

For messages with multiple attachments or non previewable attachments, the tooltip consists of a summary display with filename, contentType, and detached file path or remote url for each attachment.


Known Issues:


Currently en-US. Localizations are accepted.

Support and Questions:

Please post to the AttachmentCount Mozillazine thread.

Version history:


AttachmentCount v2.3: 168
AttachmentCount v2.0: 143
AttachmentCount v1.7: 156
AttachmentCount v1.6: 57
AttachmentCount v1.4: 113
AttachmentCount v1.3: 89

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