HDMI 2.1 on Mac: How the Latest macOS Expands External Display Support

Why high refresh rate support matters

HDMI version 2.0 tops out at enabling 4K UHD 60Hz refresh rate displays, which is fine for clarity but feels sluggish compared to today’s 90–120Hz phones and tablets. HDMI 2.1 introduces FRL (Fixed Rate Link), enabling modes up to 4K 240Hz or 8K 60Hz - provided the OS, GPU, adapter, cable, and display all support them. With 4K 100–144Hz HDMI monitors now common for gaming and productivity, bringing higher refresh rates to the Mac meaningfully improves scrolling, animations, cursor movement, and overall visual comfort.

What changed in macOS

Historically, Apple silicon Macs could drive high-resolution panels above 60Hz when connected via DisplayPort Alt Mode, yet USB-C to HDMI adapters were effectively limited to HDMI 2.0 features (4K 60Hz). Some USB-C to HDMI adapters worked around this by spoofing DisplayPort, occasionally enabling 4K 120Hz - but with inconsistent results and without official support. The latest macOS adds native USB-C to HDMI 2.1 FRL support, enabling high-resolution, high-refresh modes on compatible Apple silicon systems when used with compliant adapters/docks and updated firmware.

Supported hardware & scenarios (at a glance)

• Apple silicon: Works with Apple silicon Macs with M3 and newer processors that can already drive high-bandwidth external displays; exact maximums still depend on each Mac’s GPU/port limits.
• Single vs. multiple displays: Systems that natively support multiple external displays (e.g., Pro/Max tiers) can now attach multiple HDMI 2.1 FRL-capable displays via compatible USB-C ports or compatible docks. Systems limited to one external display still benefit from higher refresh on that single output.

Clamshell caveat: Apple MacBook Air and MacBookPro 13-inch with M3 and macOS can support up to two external displays with the lid closed - this requires connecting at least one external display, power, mouse and keyboard before closing the laptop lid.

What you’ll need for 4K 120Hz (and higher)

1. A compliant USB-C to HDMI 2.1 FRL adapter or dock (with the latest firmware).
2. A certified Ultra High Speed HDMI cable (48 Gbps).
3. A display that supports the target mode (e.g., 4K 120Hz via HDMI 2.1 FRL).
4. A Mac and macOS version with FRL support enabled (macOS 26 and newer)

Correct macOS display settings (you may need to set resolution/refresh rate explicitly in the System Settings - Display settings menu).

Plugable gear that’s ready (with firmware updates)

• USB-C to HDMI 2.1 8K Adapter (USBC-HDMI8K): Connects directly to your Mac’s USB-C port to provide an HDMI 2.1 output. A firmware update enables higher refresh rate modes with macOS 26+ on Apple M3-M5 MacBooks.
• USB-C 5-Display Dock with HDMI 2.1 + 140W charging (UD-7400PD): One “HDMI 8K” port is GPU-native and can support 4K 120Hz (or up to 8K 30Hz on supported hosts). The dock’s DisplayLink-driven HDMI output remains HDMI 2.0 (4K 60Hz). Firmware updates enable the macOS FRL benefits on supported Macs.

Firmware will generally be found on the product page, Plugable will provide update tools for both Windows and macOS whenever possible, with step-by-step guides and email support.

Practical notes for IT and power users

• Cable quality matters: Use certified Ultra High Speed HDMI cables or better to avoid FRL link drops.
• Adapter firmware: Update before engaging higher refresh modes; mismatched firmware can force fall-back to TMDS (HDMI 2.0-like behavior).
• Mixed environments: If you support both Windows and macOS, the same Plugable adapter/dock can deliver 4K 120Hz on capable PCs and - now - on Macs with macOS 26+.
• DisplayLink vs. native paths: FRL applies to the GPU-native HDMI path. DisplayLink outputs in docks still top out at 4K 60Hz by design, which is ideal for office workflows but not intended for graphically intensive, or color-critical work.

Quick FAQ

Does this enable multiple 4K 120Hz displays on every Mac?

No. You’ll still be bound by each Mac’s GPU and external display limits. FRL simply unlocks higher-bandwidth HDMI modes with supported hosts and displays.

Will existing Plugable USB-C to HDMI adapters work?

If they use an HDMI 2.1 FRL-capable bridge and you install Plugable’s firmware update, yes. Check the product page for compatibility notes and the update package.

What about when using clamshell mode?

Where supported, clamshell can allow additional modes by disabling the internal panel, freeing bandwidth for external outputs.

If you’re deploying at scale, start with a small pilot: validate your Macs, monitors, cables, and adapters on the target macOS, then roll out via your standard image/update process. This reduces edge-case surprises and keeps your team productive.