This applies to any social feed page that sends notifications, which includes Announcements, Social Feed and Crowd Pics pages.

You can write as long an announcement as you need. Nothing is truncated inside the app — when somebody opens the post, they see all of it.

What appears on somebody's lock screen is cut off. Roughly the first 100 characters, though the exact amount depends on their phone, their operating system version and their own notification settings. You cannot control it and you cannot rely on a particular number.

Many people read the notification and never open the app, so treat it as the whole message rather than a teaser.

This is the one thing worth changing about how you write announcements.

"Buses leaving at 4pm from the north entrance, not the main doors" works on a lock screen. Somebody who reads only that knows what to do.

"We have an important update about transport this afternoon. Please read on for details." tells them nothing. They have to open the app to learn anything, and most will not.

The same applies to a time or a room number. Lead with it rather than building up to it.

Write the short version as the announcement, and put the detail where it belongs — a Documents page for a schedule or a deck, or a Rich Text page for anything that needs formatting. Then the announcement can say what changed and where to look.