Depending on how many people you'd like to notify, you have a few options for making announcements in Slack using mentions. Read on to learn how to send your message to everyone in Slack or just everyone in a specific channel. 

What to expect

• @everyone notifies every person in the the general channel, @channel notifies all members of a channel, and @here notifies only the active members of a channel.
• These mentions won't notify people when their notifications are paused, or when they're used in threads.
• In channels with at least six members, Slack will ask you to confirm before you send a message with any of these mentions. Owners and admins can turn this warning off.
• On the Enterprise Grid plan, these mentions work differently in channels. If there are 10,000 members or more, only owners and admins can use @channel and @here. 

We suggest using these mentions sparingly. If you need to get the attention of someone specific, you can mention that person directly. On the Pro, Business+, and Enterprise Grid plans, you can also notify a specific group of people by creating a user group.

Note: Owners and admins with permission can choose to restrict who can use @everyone, @channel, and @here. If you don’t have the option to notify a channel or workspace, find an owner and ask for help.

@everyone

@everyone can only be used in the general channel, which is a channel that all members (except guests) are automatically added to. This mention will notify everyone in the general channel whether their availability is set to active or away.

When to use @everyone

• Give your organization information about a new vacation policy.
• Alert everyone in the company about an emergency evacuation drill.

Note: By default, guests aren't able to use @everyone.

@channel

Use @channel to let everyone in a channel know about timely, relevant information. This will trigger a desktop or mobile notification for all members of the channel, whether their availability is set to active or away.

When to use @channel

• Update your team about a last-minute change to a project deadline.
• Let members know when you adjust a work process or the channel structure.

Tip: If you're building a Slack app that can notify members, the message from your app's bot user must contain <!channel> or <!everyone>.

@here

Use @here when you only need the attention of people who are actively working in any channel you’re a member of. This is great for when you don’t want to notify coworkers who aren’t available at the time. 

When to use @here

• Schedule an impromptu event for people who are available, like a lunch outing.
• Get a question answered quickly by coworkers who are on Slack.