PowerPoint files that are larger than 30 MB can't be shared in a meeting from Skype for Business on Mac. Workaround: Open the PowerPoint file on the computer and share the screen in the meeting. Contact card information for the signed-in user is out of date.

Messages User Guide

When you’re having a conversation with someone in Messages, you can share your screen with them, or they can share theirs with you. It’s a great way to work together on a project or help a friend do something on their computer.

Share a screen

1. In the Messages app on your Mac, send a message to the person you want to share with, then click Details.

   You can’t send a message to someone who’s restricted by communication limits in Screen Time.

2. Click the Screen Share button , then do one of the following.

   • Share your screen: Choose Invite to Share My Screen.

   • View your friend’s screen: Choose Ask to Share Screen.

   When the screen-sharing request is accepted, an audio call begins automatically (so you can talk while you work) and the Screen Sharing app opens. For information about using the Screen Sharing app, see Share the screen of another Mac.

3. To stop screen sharing, do one of the following:

   • If you’re sharing your screen: Click in the menu bar, then choose End Screen Sharing. (If you’re not ready to stop yet, choose Pause Screen Sharing; choose it again to resume sharing.)

   • If you’re viewing your friend’s screen: Choose Screen Sharing > Quit Screen Sharing.

Tip: Don’t want someone to send you screen-sharing invitations? When you receive an invitation from them, hold the pointer over the Decline button, click , then click Block.

If you can’t share a screen

In the Messages app on your Mac, if the Screen Share button is dimmed, try the following:

• Make sure the person youʼre trying to share with is signed in to iCloud using the same Apple ID they used to sign in to Messages.

• If they can’t sign in to iCloud and Messages using the same Apple ID, open your Contacts app, and make sure your contact card for the person includes both Apple IDs—the one they use to sign in to iCloud, and the one they use in Messages. Then try sharing again. (See Create a contact card.)

Tip: You can also share screens without using the Messages app, using macOS screen sharing. See Turn Mac screen sharing on or off.

Allow someone to control your screen

When you share your screen with someone, you can also allow them to control your screen, which gives them complete access to your computer.

WARNING: Only allow people you trust to control your screen. They can do anything you can do on your computer—open apps, create or delete documents, copy files from your computer to theirs, and so on.

On your Mac, do one of the following:

• If you received an invitation to share your screen: Click Accept in the invitation. A message asks if you want to let the other person control your screen, or just observe it. Select “Control my screen,” then click Accept.

  If something screwed in my hardware? Mac os mavericks dmg2img.

• If you want to initiate screen sharing: Invite your friend to share their screen. After they accept, click in the menu bar, then choose “Allow [name] to control my screen” so there’s a checkmark next to it.

To take back control of your screen—but still let the other person view it—click in the menu bar, then choose “Allow [name] to control my screen” to remove the checkmark.

If you donʼt give someone screen control, they can still click to highlight areas on your screen.

Recently Microsoft released a new update for Skype for Mac which bumped the app to v8.52.0.145. The latest update brought features like the ability to share a contact with someone in your contact list. Unfortunately, it also broke screen sharing on Skype for Mac users.

According to a thread on Microsoft Answers Community forum, users are unable to share their apps to other users. Microsoft hasn’t released an official statement or a workaround but the original poster found a way to make it work until the bug is fixed.

• Go to System Preferences>Security and Privacy.
• Scroll down until you see Screen Recording and click the Skype checkbox (Skype will close to apply the changes).
• Reopen the app and make a test call to see if the problem has been resolved

Unfortunately, it isn’t clear if the issue was because of Microsoft’s new update as many apps are behaving weirdly on Apple’s new macOS Catalina.