USB-C Introduction: What is USB-C DisplayPort (DP Alt Mode)

2025-06-30

USB-C connector has now been taking over the world.

USB-C helps connect everything from your laptop and phone to monitors and storage devices. For years, USB-A was the standard, but now USB-C is the connector you see everywhere.

Introduced in 2014, USB-C was designed to replace all previous USB ports with one smaller, reversible, and more powerful standard. It supports charging, data, video, and more all through one port. But here’s the common frustration: You plug in your monitor, the cable charges your laptop—but the screen stays black.

Here’s the catch: not all USB-C ports are the same. Some charge your laptop. Some send video to a monitor. Some only transfer files. And unless you check your device specs carefully, you might end up with a USB-C port that can’t do what you need.

So, what do you need to know about the USB-C connector? This article will help you explore and answer the following key questions and topics:

What is USB-C?

Do all USB-C capabilities support Display or Charging?

What is USB-C DisplayPort (DP Alt Mode)?

How Do I Know If My USB-C Supports All Mode?

How Do I Know If My Monitor Supports USB-C Charging?

Are USB-C and Thunderbolt compatible?

FAQs About MacBook^® and USB-C Monitors

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What is USB-C?

USB-C is a universal port that handles power, data, and sometimes video all through one cable. It replaced older standards like USB-A and Micro-USB by offering a smaller, reversible design with more capabilities. USB-C is now standard on most modern laptops, including all MacBook models but not all USB-C ports support the same features. Some only charge. Some transfer files. Some send video. That’s why it is important to understand what your device’s USB-C port actually supports. This single port can support data, charging, video output, and even audio—depending on the device.

Here’s what USB-C can potentially support—depending on the device:

Feature	What it does	What it means for you
Feature Reversible connector	What it does Plug in either way—no flipping needed	What it means for you Easier to use, less wear and tear
Feature Power Delivery (PD)	What it does Provides up to 100W of power	What it means for you You can charge laptops, phones, and accessories
Feature Alt Mode	What it does Sends video—and sometimes audio—via DisplayPort, HDMI, or other interfaces	What it means for you Lets one USB-C port carry multiple signals through a single cable (data, video, audio, power)
Feature Audio output	What it does Converts digital audio to analog	What it means for you Lets you use USB-C headphones or adapters

Of the four USB-C features, only reversibility is guaranteed across all ports. Support for video output, charging, and audio depends on how each manufacturer designs their hardware. That’s why checking device specs—or testing in real use—is so important.

Not every USB-C device supports all of these. That’s why it’s important to check your device’s specs or test it in real use.

Do all USB-C capabilities support Display or Charging?

No—and this is where most people get confused. Just because a device has a USB-C port doesn’t mean it can charge your laptop or connect to a monitor. Some USB-C ports are data-only, while others support video output (via DP Alt Mode) or Power Delivery (PD) for charging. Always check your device’s official specs to confirm what the port supports. Of the four USB-C features, only reversibility is guaranteed across all ports. Support for video output, charging, and audio depends on how each manufacturer designs their hardware. That’s why checking device specs—or testing in real use—is so important.

What is USB-C DisplayPort (DP Alt Mode)?

DisplayPort Alt Mode (DP Alt Mode) is one of USB-C’s most powerful and most misunderstood features. It enables certain USB-C ports to send video signals to external monitors using the DisplayPort protocol, all through a single cable.

But not all USB-C ports support DP Alt Mode, and many brands don’t clearly label whether they do. That’s why some users find their device charges just fine over USB-C, but fails to show any picture on a monitor.

How Do I Know If My USB-C Supports All Mode?

Standard USB-C

(No Thunderbolt)

Thunderbolt 1&2

Thunderbolt 3&4

(USB-C connector)

* While Thunderbolt 3 and 4 look identical, they differ in minimum requirements and capabilities. Use the table above to compare what each supports.

There’s no universal label for DP Alt Mode on USB-C ports, and some brands don’t mark them clearly even if supported. The most reliable way is to check your device’s official tech specs.

Most MacBooks (M1/M2/M3/M4) support video output over USB-C
Many Windows laptops support it, but not all—especially entry-level models
On tablets and phones, DP Alt Mode is much less common

You can also test it directly: use a USB-C monitor that supports DP Alt Mode and a full-featured USB-C cable (not a charge-only cable). If nothing shows up, try switching ports or cables.

USB Type-C in the Real World (Laptop)

What You Want to Do	Required Feature	Supported By
What You Want to Do Charge your laptop	Required Feature Power Delivery (PD)	Supported By USB-C PD, Thunderbolt 3/4
What You Want to Do Connect to a 4K monitor	Required Feature DisplayPort Alt Mode	Supported By USB-C DP Alt Mode, Thunderbolt 3/4
What You Want to Do Use one cable for display + charging + data	Required Feature Alt Mode + PD + Data	Supported By Thunderbolt 3/4, full-featured USB-C
What You Want to Do Transfer files only	Required Feature USB 3.1 / 3.2 (Gen1/2)	Supported By All USB-C data cables
What You Want to Do Max speed (40 Gbps) + pro workflows	Required Feature Thunderbolt 4	Supported By MacBook Pro® (2021+) + TB4 cables
What You Want to Do Connect multiple monitors with one cable	Required Feature Daisy Chain with Thunderbolt	Supported By Thunderbolt 3/4 only (USB-C does not support video daisy chaining)

Learn more about how to Daisy Chain

*Not all laptops and mobile phones with USB-C ports support full USB-C function—so always check for terms like “DP Alt Mode,” “PD,” or “Thunderbolt” on your device and cable.

**Laptops and mobile phones have different combinations of USB-C functions.

Due to the various specifications and compatibility of the Type-C connector, BenQ InstaShow Wireless Presentation System presents the ultimate solution with its smart self-detecting technology, which can automatically show whether your laptop or mobile device with Type-C port supports Alt Mode output and therefore provide better intuition within your user experience.

How Do I Know If My Monitor Supports USB-C Charging?

If you want to connect your laptop to a monitor using just one USB-C cable—for both display and charging—your monitor must support USB-C Power Delivery (PD).

But how do you check for that? Here’s what to look for:

What to look for	How to check
What to look for The monitor’s spec sheet or product page	How to check 1. Look for phrases like: “USB-C with Power Delivery“, “PD 65W“ or “USB-C charging up to 90W“, “Charge your laptop via USB-C“ 2. Spec listed like: “USB C (PowerDelivery 90W, DisplayPort Alt Mode, Data)”
What to look for Some models have a battery or power icon next to the port to indicate charging support
What to look for If it works with a known charging-capable laptop and cable	How to check Try it.

Example: MacBook Air^®+ USB-C Monitor

If you're using a MacBook Air (M1, M2, M3, M4), it can be charged via USB-C with as little as 30W to 45W of power. That means:

A monitor that supports USB-C PD at 60W or above can easily power your laptop while delivering video over the same cable.

Some BenQ monitors go even further in delivering power and flexibility.

The BenQ MA Series offers 90W USB-C Power Delivery, plus an additional 15W USB-C port—perfect for charging your iPhone^® or iPad^® at the same time.
For advanced users, the PD2730S and PD3226G feature Thunderbolt 4 with 90W Power Delivery, along with a 15W Thunderbolt 4 port for high-speed peripherals. These models are a great match for most MacBook Pro^® users, offering stable power and bandwidth for daily creative workflows. For devices that require 96W, the 90W output may charge slightly slower, but is fully compatible.

These models eliminate cable clutter—providing 90W charging for your MacBook, seamless 4K or 5K display output, and additional power for your peripherals, all through a single cable.

Are USB-C and Thunderbolt compatible?

Yes—but compatibility depends on what you're trying to do.

USB-C and Thunderbolt ports use the same connector, so they’re physically compatible. You can plug a USB-C device into a Thunderbolt port, and vice versa—but that doesn’t guarantee full functionality.

For example, a USB-C monitor will usually work with a Thunderbolt port for display and charging, as long as it supports DP Alt Mode and Power Delivery. But not all USB-C ports support Thunderbolt-level speed, daisy chaining, or PCIe accessories.

USB 3.1 Gen 2, Thunderbolt 3, and Thunderbolt 4 may look alike, but their performance and feature sets are quite different. The table below compares the key differences at a glance.

Feature	Type-C	Thunderbolt 3	Thunderbolt 4
Feature Max Bandwidth	Type-C 10 Gbps	Thunderbolt 3 Up to 40 Gbps (varies by device)	Thunderbolt 4 40 Gbps (guaranteed)
Feature Video Output	Type-C Optional (via DP Alt Mode)	Thunderbolt 3 Optional (depends on device)	Thunderbolt 4 Required (dual 4K or 1×8K)
Feature Power Delivery	Type-C Optional	Thunderbolt 3 Up to 100W	Thunderbolt 4 Up to 100W (PD 3.0/3.1)
Feature PCIe Support	Type-C ❌	Thunderbolt 3 Optional	Thunderbolt 4 Required (min PCIe x4)
Feature Daisy Chain	Type-C ❌	Thunderbolt 3 Optional	Thunderbolt 4 Required
Feature MacBook Examples	Type-C MacBook (Retina, 2015–2017)	Thunderbolt 3 MacBook Air (M1–M3), MacBook Pro 13” (M1/M2)	Thunderbolt 4 MacBook Pro 14” / 16” (M1/M2/M3)

Learn more about what sets Thunderbolt apart from USB-C and earlier versions?

FAQs About MacBook and USB-C Monitors

• Does charging through a monitor hurt my MacBook’s battery?

No. Charging your MacBook via a USB-C monitor is completely safe, as long asif the monitor supports Power Delivery (PD) and delivers sufficient wattage. macOS^® manages power input intelligently, so your battery is protected from overcharging or overheating.

In this case, the monitor’s USB-C functionality has been tested by an Authorized USB-IF Test Lab to verify safe power delivery and MacBook compatibility—ensuring it charges your device reliably without compromising battery health.

• Why isn’t my MacBook charging from my USB-C monitor?

This could be due to one of four reasons:

1. The monitor doesn't support USB-C Power Delivery, or the output wattage is lower than what your MacBook requires.

2. The monitor is off or in a power-saving mode.

3. You're using a charge-only or low-wattage USB-C cable

4. Your MacBook is connected to the wrong port.

Try using a certified USB-C PD cable and double-check the monitor’s specifications for power output

• My USB-C monitor charges my Mac^®—but there’s no picture?

Your monitor might only support charging, not video. To display content, both the MacBook and the monitor must support DP Alt Mode. Also ensure your cable supports both video and power, and the monitor is set to the correct input source.

• I’m charging my MacBook from a USB-C monitor. Can I plug in my iPad^® too?

Yes—if the monitor offers an additional USB-C or USB-A port with Power Delivery. For example, BenQ’s MA Series includes a secondary 15W USB-C port ideal for charging an iPad or iPhone while your MacBook stays connected.

• Can I just buy any USB-C cable and expect it to work?

No. USB-C only refers to the shape of the connector—not what it can do. Some cables only charge. Others support video, data, or high-wattage power. Always check for labels like “4K,” “PD,” or “Thunderbolt Certified.”

• Do I need a special cable to connect my MacBook to a USB-C monitor?

Yes. Use a full-featured USB-C cable that supports both video and charging. Avoid USB-C cables designed only for power or data transfer. Look for specs like “4K video,” or “PD” when buying.

• What if my Mac is not detecting the monitor?

Try the following:

1. Use the correct input source on your monitor (USB-C)

2. Restart your Mac with the monitor plugged in

3. Use a different USB-C port or cable

4. Go to System Settings > Displays and click Detect Displays

• How do I know if my USB-C supports DP Alt Mode?

To confirm if your MacBook supports DisplayPort Alt Mode over USB-C:

1. Check Apple’s official specs: Most MacBook Air and Pro models with M1, M2, M3, or M4 chips support video output via USB-C. Look for “Display Support” or “Thunderbolt / USB 4” in the technical specs.

2. Use a USB-C monitor and a known good cable: If your monitor doesn't display anything, make sure the cable supports both power and video (DP Alt Mode), and that you're using the correct USB-C port on your MacBook (some hubs have data-only ports).

3. Avoid charge-only cables: These won’t transmit video, even if the devices support it.

If your MacBook is from 2020 or later, it's very likely to support DP Alt Mode via USB-C. The most common issue is using a cable that only charges but doesn’t support video transmission. All MacBooks with Thunderbolt 3 / 4 or USB 4 ports support DisplayPort Alt Mode.

• Do I need a Thunderbolt monitor for my MacBook?

Unless you have specific high-performance needs.

Most MacBooks support DisplayPort over USB-C, so a regular USB-C monitor with DP Alt Mode works perfectly for everyday tasks like browsing, streaming, or even photo editing.

Choose a Thunderbolt monitor only if you need daisy-chaining, external SSDs, or rely on a Thunderbolt dock for accessories.

*MacBook^®, MacBook Pro^®, MacBook Air^®, macOS^®, Mac^®, iPhone^®, and iPad^® are registered trademarks of Apple Inc.