How to start a new message in Slack on Mac: sidebar, ⌘N and Slack Connect

The quickest route: the sidebar plus button

Slack's help center describes the plus button first when it explains how to start a direct message on desktop. Look at the sidebar on the left side of the Slack window. Click the plus button, and Slack starts a new direct message for you. You do not need to open a menu or remember a shortcut. This route suits the most common case, which is a quick message to one colleague who is already in your workspace. It is also the route to try first if you are new to the app.

Think of the plus button as the fastest route, not the only one. The rest of this guide covers the DMs list, the keyboard shortcut, and Slack Connect for people outside your company. Each route ends in the same place, a message you can type and send.

Start from the DMs list

Some people like to see their existing conversations first. In the sidebar, click DMs to open the list of your direct messages. Then click the new message icon to compose a new DM. Slack's help center describes this as the way to compose a new DM on desktop. Use this route when you want to check whether a conversation with that person already exists. Reusing an open DM keeps your history in one place.

Use ⌘N when your hands are on the keyboard

Slack's keyboard shortcuts page lists Compose a new message as ⌘N on Mac. The ⌘ key is the Command key, which sits on either side of the space bar. Hold it and press N with the Slack window in front. You stay on the keyboard the whole time, so you never reach for the trackpad. It is the one shortcut to learn first if you write messages all day.

If ⌘N seems to do nothing, check two things. First, make sure Slack is the active app, not your browser or Finder. The app name next to the Apple menu at the top left tells you which app has focus. Second, click once inside the Slack window and try again. Shortcuts only respond when Slack is in front.

Compare the routes at a glance

Pick the route that matches the job. A quick question to one person fits the plus button. A message that needs a list of people to check suits the DMs list. A message to someone at another company needs Slack Connect, which is covered below.

Message someone at another company with Slack Connect

A normal direct message works inside one workspace. To reach someone at another company, use Slack Connect. On desktop, go to Home, then Directories, then External. Click Start a DM in the top right corner. Enter the recipient's email address. Then click Send Invitation.

The DM does not open right away. The recipient must accept the Slack Connect invitation first. If you already share channels with people from their company, you can message them without an invitation. Check the channels you share before you send a new invitation.

When Directories is missing or invitations fail

Some workspaces show a different layout. On desktop, look for an External connections tab in the sidebar instead, and click More if you do not see it at first. If you still cannot send or accept invitations, the workspace may restrict Slack Connect DMs. Owners and admins can set those permissions. Ask one of them to check your access.

Worked example: a question for a teammate

Say you need a teammate to confirm a due date for a report. Start with the plus button, because you only need one person. Type the question in a short, plain message. If the answer affects a few more people, open a group DM instead. Then name the group so you can find it later.

Start a group message and name it

A DM can be one-to-one or a group. Slack's help center says a group DM can include up to nine people. Count the people before you start the group, so you know whether a DM still fits.

Group DMs do not have a name at first. To name one, open the group DM. Hover over the member names at the top. Click the pencil icon, type a name, and click Save. A clear name makes the group easier to find when you search later.

Mistakes people make when starting a message

• Looking for a File menu item. The official help pages do not describe one for new messages, so use the sidebar or ⌘N instead.
• Trusting the ⌘⇧K shortcut. The shortcuts page shows it beside both compose and Browse DMs, so test it before you rely on it.
• Using the normal plus button for someone at another company. Use Slack Connect, which has its own steps.
• Sending the invitation again and again. The recipient has to accept it, and repeats do not replace that step.
• Assuming the web app looks the same. The help pages checked did not confirm the same buttons in a browser.
• Skipping the name on a group DM. An unnamed group is harder to find later when you search.

Mobile uses a different path

This guide covers the Mac app only. The help center describes a different path on phones. Tap the compose button at the bottom of the Home tab, select Message with external people for Slack Connect, then tap Share to send the invitation. The Mac steps above do not match that flow.

Fix a new message that will not open

Slack's troubleshooting article covers several problems. These include Loading trouble, Connectivity failure, WebSocket trouble, and Server error. Start with the cache fix for the first three. Use the reload fix for server errors.

Go to Help > Troubleshooting > Clear Cache and Restart. The app restarts and clears its cache. If the problem continues, go to Help > Troubleshooting > Restart and Collect Net Logs. Support may ask for those logs, so share them only with people you trust.

Reload the window for server errors

A server error is different from a bad connection. Slack's help center gives a Mac-specific fix for it. Press ⌘R to reload the window. If the error returns, restart the app and try the cache fix above.

Check your version before you troubleshoot

Slack's help articles do not carry a version number or a last updated date. That makes it hard to tie steps to one release. The Slack for Mac release notes list version 4.53.280, dated November 3, 2026, as the latest entry this guide could verify. If your app is on an older build, menus may differ, so compare what you see with the current help pages.

This guide does not give a menu path for finding your version number. The official help pages do not list one. Use the release notes to compare builds only after you have the number from your own app.

Do you need a DM or a channel?

Use a DM when the message belongs to one person or a small group. Use a channel when the topic needs more people to follow along. Slack's help center explains direct messages on its own page, so read it if the choice is still unclear. Pick the route that fits who needs to see the message.

Where to go next

Once the message is sent, you may need to find something from earlier. The guide to searching messages in Slack on Mac shows the search steps. If you need to follow replies, the threads guide explains how to find them. For a fresh start on unread messages, read how to mark all messages as read in Slack on Mac.