| You have a few excellent options for controlling two Macs with a single keyboard (and mouse/trackpad). The best solution depends on your macOS versions and specific needs. 
1. Recommended Solution: Universal Control (Apple's Built-in Feature)Universal Control allows you to use a single keyboard, mouse, or trackpad across up to three Mac or iPad devices. It's seamlessly integrated into macOS and is the easiest solution if your devices meet the requirements. What It IsA macOS feature that lets your pointer and keyboard flow between nearby Macs and iPads, treating them as extensions of your primary device. 
Requirements- macOS Versions:
- Primary Mac: macOS Monterey 12.3 or later.
- Secondary Mac: macOS Monterey 12.3 or later.
- Apple ID: All devices must be signed in with the same Apple ID using two-factor authentication.
- Connectivity: Bluetooth, Wi-Fi, and Handoff must be enabled on all devices.
- Proximity: Devices need to be physically close to each other (within ~10 meters/30 feet).
- Other: Mac models must be 2016 or newer. (A full list of compatible models can be found on Apple's support page).
How to Set It Up1. Enable Handoff on Both Macs: - On both Macs, go to
System Settings (or System Preferences on older Monterey versions) > General > AirDrop & Handoff. - Ensure "Allow Handoff between this Mac and your iCloud devices" is checked.
2. Enable Universal Control on Both Macs: - On both Macs, go to
System Settings > Displays. - Click the "Universal Control..." button (you might need to scroll down).
- Check these options:
- "Allow your pointer and keyboard to move between any nearby Mac or iPad."
- (Optional, but recommended) "Push through the edge of a display to connect a nearby Mac or iPad."
- (Optional) "Automatically reconnect to any nearby Mac or iPad."
- Click "Done."
3. Arrange Your Displays: - In
System Settings > Displays, you will see visual representations of your connected Macs. - Drag and drop the display icons to match their physical arrangement on your desk. This tells your Mac which edge to "push" the cursor through.
How to UseSimply move your mouse pointer (or finger on a trackpad) to the edge of your primary Mac's screen, and it will smoothly transition to the secondary Mac, allowing you to control it with the same keyboard and mouse. 2. Alternative Software Solutions (if Universal Control isn't an option)If your Macs don't meet Universal Control requirements (e.g., older macOS versions, different Apple IDs, or you need cross-platform compatibility), dedicated software solutions are available. 
Synergy (Paid)- What It Is: A robust software KVM (Keyboard, Video, Mouse) switch that allows you to share a single keyboard and mouse across multiple computers with different operating systems (macOS, Windows, Linux).
- How It Works: One computer acts as the "server" (the one connected to your keyboard and mouse), and the others are "clients." They communicate over your local network.
- When to Use:
- When one or both Macs have an macOS version older than Monterey 12.3.
- If you need to control a non-Mac computer alongside your Mac.
- For more advanced customization and features.
Barrier (Free & Open-Source)- What It Is: Barrier is a free and open-source fork of Synergy 1. It provides similar functionality without the cost.
- How It Works: Identical to Synergy, one machine acts as the server, and others as clients, communicating over the network.
- When to Use: If you need Synergy's features but prefer a free, open-source solution.
3. Hardware Solution: KVM Switch (Less Common for Keyboard Only)A KVM (Keyboard, Video, Mouse) switch is a hardware device that allows you to share a single keyboard, mouse, and often a monitor between multiple computers. 
What It IsA physical box with ports for connecting your keyboard, mouse, monitor, and multiple computers. You press a button on the switch to instantly toggle control between connected computers. When to Consider- Sharing a Monitor: If you also want to share a single monitor between your two Macs, a KVM switch is a viable option.
- Hardware Reliability: For mission-critical tasks where software solutions might introduce latency or unreliability.
- Security/Isolation: In environments where network-based software solutions are restricted or not preferred.
- Drawbacks: More expensive, requires extra cables, takes up physical space, and might be overkill if you only need to share a keyboard.
General Tips- Network Connectivity: For all software solutions (Universal Control, Synergy, Barrier), ensure both Macs are connected to the same Wi-Fi network or physically wired into the same local network for optimal performance.
- macOS Updates: Keep your macOS up to date to ensure compatibility and access to the latest features like Universal Control.
- Troubleshooting: If you encounter issues, try restarting both Macs, checking your network connection, and re-verifying the settings in System Settings > Displays (for Universal Control) or the respective software.
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