Do I need an e-marked cable? Yes, if you charge a laptop above 60W. An e-marked cable has a small chip in its connector that tells your devices what the cable can safely carry. Without that chip, a USB-C cable is treated as a basic cable limited to 3A and 20V, which is 60W. For a phone or earbuds you rarely need one. For a 100W laptop charger you do, under the USB-C rules. This guide explains what the chip does, when it matters for charging, data, and video, and how to check your cable.
Quick answer: You need an e-marked cable for any USB-C connection that carries more than 60W, which means a 5A cable. The chip stores the cable's current, voltage, and signal ratings so your devices can negotiate safely. A cable without one is treated as 3A and 20V. Below 60W, a basic cable is enough. For fast data and video, check the cable's listed speed and video support.
What an e-marked cable is
An e-marked cable is a USB-C cable with a small chip in the connector that reports the cable's ratings. The chip, called an e-marker (electronic marker), stores the cable length, maximum current and voltage, signal type, and alternate mode support. During USB Power Delivery negotiation, the charger and the device read that data before they agree on how much power to send, as Total Phase explains.
Do I need an e-marked cable? The 60W rule
You need one whenever the cable has to carry more than 60W, and fast data and video depend on the cable's rating too.
| What you are doing | Cable you need | E-marker? |
|---|---|---|
| Charging a phone or earbuds, up to 60W (3A at 20V) | A basic USB-C cable | Not required |
| Charging a laptop at 65W to 100W | A 5A cable | Yes |
| Moving data at 5 or 10 Gbps | A cable rated for that speed | Check the listing |
| Sending video through a USB-C hub | A cable that lists video support | Check the listing |
What happens without an e-marker
A cable without an e-marker falls back to safe defaults, usually 3A, 20V, and slower data. At 3A and 20V the limit is 60W, so a 100W charger on a basic cable charges at up to 60W. A cheap cable may also carry data only at USB 2.0 speeds, up to 480 Mbps. A charging-only cable may lack what stable video needs, which shows up as a "no signal" screen. KTC's cable guide covers the same limits.
How to check whether a cable is e-marked
You cannot see the chip, so you have to read the product listing.
- Look for the words "e-marked", "5A", or "100W" in the listing.
- Look for a printed speed rating, such as 10 Gbps.
- If the cable will carry video, look for a statement of video support.
- Avoid cables sold without clear specs, because a basic cable can look identical.
Which cable to use with a USB-C hub
With a hub, one cable between the hub and your laptop can carry charging, data, and video together, so the cable's rating matters more than it does for a phone charger. Use the cable the hub maker supplies or recommends, and match it to the job.
- For laptop charging above 60W, use a 5A e-marked cable.
- For fast drives, use a cable with a printed 10 Gbps rating.
- For an external monitor, use a cable that lists video support.
What an e-marked cable does not do
An e-marker guarantees a cable's ratings, not the performance of the devices on each end.
- It does not raise your charger's output. A 65W charger still delivers 65W.
- It does not add video to a USB-C port that has no video output.
- It does not make a slow drive or a slow port faster.
- A listing that says "e-marked" is the seller's claim, and you cannot confirm the chip by looking at the cable.
Frequently asked questions
Most e-marker questions come down to power above 60W.
Do I need an e-marked cable for 100W charging?
Yes, under the USB-C rules. Charging at 100W means 5A at 20V, and a cable rated for 5A must carry an e-marker chip. Without one, a USB-C cable is treated as a 3A cable, which caps charging at 60W.
What does an e-marker chip do?
It tells your charger and device what the cable can safely carry. The chip stores the cable's current and voltage rating, its signal type, and other details. The two devices read it before they agree on how much power to send.
Can I use any USB-C cable with a USB-C hub?
Not always. A basic cable can work for low-power accessories, but it may cap power, data speed, or video. Use a cable rated for the speed and power you need, and read the cable's listing or the hub maker's guidance.
How can I tell if a USB-C cable is e-marked?
You cannot see the chip. Check the product listing for the words e-marked, 5A, or 100W, plus a printed speed rating. Be careful with cables sold without clear specs, because a basic cable can look identical.
Next steps
Check the listing of every cable you use for charging, data, or video, and keep the cable that came with your hub. If you want a hub for one-cable laptop setups, see the Gitfos C1Pro, browse more hubs and charging options, or reach the team through the support center. More buying advice lives in the Guides blog.