Not all USB-C cables are equal: how to buy one that won't throttle your charge
Not all USB-C cables are equal: how to buy one that won't throttle your charge
Your fast charger is only as fast as the cable you plug into it. Two leads can look identical and perform worlds apart — here's how to tell them apart. From £6.49.
You buy a proper fast charger, plug in the cable that came free with something years ago, and wonder why charging still crawls. The cable is the quiet bottleneck. It carries no branding, gives no warning, and can throttle a 100W charger down to a trickle. Here's what actually separates a good cable from a slow one.
The short version
Three things decide a USB-C cable's real-world speed: its power rating (60W vs 100W/240W), whether it has an E-marker chip for high wattage, and its data speed if you move files or video. Match the cable to the job — the flagship 100W 4K E-marker cable does all three (£15.99); a good everyday USB-C lead starts at £7.99.
01Why two identical-looking cables aren't
From the outside, USB-C cables are twins. Inside, they're not. Cheaper leads use thinner wire and skimp on shielding, so they can't carry high power or fast data without losing it as heat. A quality cable uses thicker conductors, proper shielding and — for high wattage — a tiny E-marker chip that tells your charger how much power it can safely send. No chip, no full speed. That's the whole difference, hidden in the jacket.
02The three numbers that matter
Ignore the marketing and look for these:
03Match the cable to the job
| What you're doing | The cable | Price |
|---|---|---|
| Fast-charge a laptop + 4K video / files | 100W 4K E-marker · 20Gbps | £15.99 |
| Everyday USB-C charging, built tough | 66W nylon-braided | £7.99 |
| iPhone (Lightning), built to survive | DurCable Steel · MFi | £13.79 |
| iPhone on a budget, in colours | Fruitywire · MFi certified | £6.49 |
04The E-marker chip, in one line
It's the single tell of a real high-power cable. The E-marker is a small chip inside the connector that certifies the cable for high wattage and tells the charger how much it can push. A cable without one is capped at around 60W no matter how good your charger is — which is exactly why a "fast" charger can still charge slowly. If you want full 100W speed, the cable needs the chip. Ours has it. Pair it with a GaN charger and nothing is holding your speed back.
Pick your cable
The right lead for charging, video or a tough everyday carry. From £6.49.
Frequently asked
What does E-marker mean on a USB-C cable?
An E-marker is a small chip inside the cable's connector that certifies it for high power and tells the charger how many watts it can safely deliver. Cables without an E-marker are limited to around 60W, so you need one to reach full 100W or 240W charging speeds.
Why is my phone charging slowly with a brand-new cable?
Usually the cable, not the charger. A thin or uncertified cable throttles the power your charger can deliver. Use a properly rated cable — ideally with an E-marker for high wattage — and make sure both ends are USB-C for the fastest charging.
Can any USB-C cable carry 100W?
No. Only cables built with thicker conductors and an E-marker chip can safely carry 100W. A standard USB-C cable typically tops out near 60W, which is why a high-power charger can still charge slowly through the wrong cable.
Does cable length affect charging speed?
A little — longer cables have more resistance, so very long, thin leads can lose some power. A well-made 1–2m cable with the right gauge and, for high power, an E-marker keeps losses minimal.