by default, the announcement will be sent to all users, but it is possible to edit the list of recipients by clicking on the visible to link
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the announcement can be sent by e-mail to the course users (check the Send this announcement by email to selected groups/users box),
add an announcement subject,
write the main announcement using the editor,
add an attachment if desired,
click Send announcement.
Note: since version 1.8.8.4, you can use tags inside your announcements (just copy-paste them). These tags will be automatically replaced by the corresponding value when sent by e-mail or displayed on the platform to users.
Announcements will appear to recipients like this on the platform: