UPDATE: This post is no longer accurate. We fixed this installer bug in April 2020. The latest Air Display host software works fine on Catalina.
The Air Display host software works great on Catalina once it’s installed. But unfortunately there’s an issue with our installer on Catalina. When you try to install Air Display, Catalina will block our installer, claiming it’s incompatible.
We are working on resolving this installer issue, but at this moment, it requires a workaround. We are very close to releasing this new version of the installer [UPDATE: As of April 9, we thought we had it done today but found a show-stopper bug.] So if you can, I would recommend just waiting a couple of days. And when we will release a new Air Display Host Software installer, we will send out a newsletter with more details. If you haven’t already, please consider signing up for our newsletter at the bottom of the Avatron home page. (Don’t worry; we don’t send out newsletters very often.)
If you really don’t want to wait, then in the meantime, you can install the Air Display Host with this workaround:
- Restart in recovery mode: Hold down ⌘R during startup.
- Launch Terminal: In the MacOS Utilities screen, pull down the Utilities menu from the top of the screen and choose Terminal.
- Enter this command (followed by the Return key), to temporarily disable SIP (System Integrity Protection):
- Restart Catalina.
- Launch Terminal, this time from the Applications ▸ Utilities folder.
- Enter this command to unmount the installer volume:
sudo mount -uw /
- When prompted, enter your Mac password. You will not see it on the screen.
- Install Air Display host and ignore the error message that Air Display Host is not suitable for this MacOS.
- Restart. (Now you can use Air Display host on Catalina. Not just for now, but even after the following steps.)
- Restart once more in recovery mode: Hold down ⌘R during startup.
- Use Terminal a final time to execute this command, to reenable SIP (you really do want SIP enabled, generally):
One more thing: After installing, normally all will be well, but on some Macs you will only see the desktop image on the Air Display screen, onto which you can drag the cursor but no windows or Finder icons. If this is the case, there’s one more step. To get the Air Display screen to update properly, you will just need to enable Screen Recording in the privacy settings. Apple has locked this down a bit recently. Please go to System Preferences ▸ Security & Privacy ▸ Privacy ▸ Screen Recording. You should see Air Display Host listed in a box at the right. Just enable its checkbox to allow it to “record the contents of your screen, even when using other apps.” (You may need to click the little padlock and enter your password to allow the change.)
Why do we have to do all of this on Catalina? Well, years ago, Apple had driver developers install kernel extensions (like Air Display’s video drivers) in the System ▸ Library ▸ Extensions folder. Then they locked down the System folder and had us install into Library ▸ Extensions.
When we made this transition, we needed to remove our old drivers, if you had them, from your System folder, before installing the new ones into the Library folder. We put that cleanup operation in the Air Display host installer. That worked fine until Catalina. Now, when you run our installer, macOS scans our installer code and says, “Hey, these guys are trying to access the System folder! That’s not allowed!” and they block us. We are in the process of modifying our installer so that it no longer does that cleanup. We will send out a newsletter when it’s ready. Thanks for your patience!