Summary
When connecting a Plugable USB-C Multi-Stream Transport (MST) adapter to a MacBook, the connected external monitors will mirror the same content rather than function as separate, independent extended displays.
This is because macOS does not support MST for multiple independent extended displays through standard MST adapters.
While the adapter may provide video output when connected to a compatible Mac, it cannot be used to create two or three independent external displays.
Applicable To
- Plugable USB-C to Dual HDMI MST Adapter (USBC-MSTH2)
- Plugable USB-C to Triple HDMI MST Adapter (USBC-MSTH3)
- Mac computers running macOS
- Compatible iPads running iPadOS
Why Does This Happen?
Multi-Stream Transport (MST) is a DisplayPort technology that allows multiple independent video signals to be transmitted through a single compatible USB-C connection.
On supported Windows and ChromeOS computers, MST adapters can provide separate extended desktops across multiple monitors, provided the computer's graphics hardware and USB-C port support the required capabilities.
However, macOS does not support MST for multiple independent extended displays through these adapters.
As a result, when connecting multiple monitors to the Plugable USBC-MSTH2 or USBC-MSTH3 on a Mac, the external monitors will mirror the same content instead of displaying separate desktops.
This limitation is related to macOS support for MST and is not a hardware defect with the Plugable adapter.
How Can I Connect Multiple Extended Displays to My Mac?
If you need multiple independent external displays on your Mac, consider a compatible Plugable docking station or graphics adapter that uses DisplayLink technology.
Unlike MST, DisplayLink uses software and USB data to enable additional external displays on compatible systems, including Macs that have native external display limitations.
DisplayLink-based products require the appropriate DisplayLink Manager software and macOS permissions.
Alternatively, some Mac models support multiple external displays natively through compatible Thunderbolt or USB-C connections. The number of supported displays depends on the specific Mac model and Apple processor.
Important Notes
- macOS does not support MST for multiple independent extended displays. Plugable MST adapters cannot bypass this operating system limitation.
- Mirroring is expected behavior. When multiple monitors are connected through the USBC-MSTH2 or USBC-MSTH3 on a Mac, they may display the same content rather than function as independent extended desktops.
- MST and DisplayLink are different technologies. DisplayLink-based products can provide additional extended displays on compatible Macs but require software installation and configuration.
- Native display support varies by Mac model. Some Macs support multiple external displays without DisplayLink, while others have more restrictive display limitations.
- iPadOS has similar MST limitations. Plugable MST adapters cannot provide multiple independent extended displays through MST on iPadOS devices.
For additional information about the adapters and their compatibility requirements, see:
Need Assistance?
If you're unsure which Plugable adapter or docking station will support your desired multi-monitor setup, please contact Plugable Support at support@plugable.com.
When contacting support, please include:
- Your Mac model and Apple processor
- Your macOS version
- The Plugable adapter or docking station you're using or considering
- The number of external monitors you want to connect
- Whether you need mirrored or independent extended displays
This information will help our support team recommend a compatible solution for your setup.
