Why Is My Mac Charging Slowly?
A Mac charges slowly for one of three reasons: an underrated USB-C cable, a charger that can't supply enough wattage for what your Mac is doing, or a software setting like Optimized Battery Charging holding it back on purpose. Here's how to tell which one you're dealing with.
Is it the cable or the charger?
USB-C cables are not all the same, even when they look identical. A cable can be rated for 60W, 100W, or 140W+, and a lower-rated cable will cap a higher-wattage charger down to its own limit — silently, with no warning from macOS. A worn or damaged cable can fall back even further, sometimes to a fraction of its original rating.
This is why swapping the charger alone often doesn't fix slow charging: if the cable is the bottleneck, a new charger changes nothing.
How to check your charger's actual wattage
- Open System Information (hold Option and click the Apple menu → System Information).
- Select Power in the sidebar.
- Look at AC Charger Information for the wattage your Mac is currently negotiating.
This tells you what your Mac is getting right now, but it won't tell you whether the cable is the limiting factor — for that you'd need to test with a different cable, or see the negotiated wattage live as you swap cables.
How to check if your cable is the bottleneck
The manual way: charge with the same charger but a different, known-good cable, and compare the wattage in System Information. If it jumps up, the original cable was capping it.
WattsConnected does this automatically — it shows the max wattage your charger has negotiated with your Mac right in the menu bar, and flags when a cable is holding back a charger that's capable of more, so you don't have to swap cables to find out.
Other reasons your Mac might charge slowly
- Optimized Battery Charging — macOS may intentionally slow charging past 80% to reduce battery wear, based on your usage patterns.
- Charging on Hold — if you're on a fixed power source (like a desk charger) and macOS has learned you'll be plugged in for a while, it may cap the charge level intentionally.
- Too many devices on one charger — multi-port USB-C chargers split wattage dynamically across connected devices, so a phone or another laptop sharing the same charger reduces what's left for your Mac.
- Battery health — a battery with high cycle count or degraded capacity can accept a slower charge rate even from a fully capable charger and cable.
The fastest way to check
Rather than opening System Information and swapping cables to isolate the problem, WattsConnected puts the negotiated wattage in your menu bar at all times and warns you the moment a slow cable or underpowered charger is the reason your Mac isn't charging at full speed — along with which of your chargers is actually your fastest.
Frequently asked questions
Does the cable affect Mac charging speed?
Yes. USB-C cables are rated for different power levels — some carry only 60W even when plugged into a 96W or 140W charger, and older or damaged cables can fall back to much lower speeds. A high-wattage charger cannot exceed what the cable is rated to carry.
How do I know if my MacBook charger is broken or just underpowered?
Check the wattage printed on the charger against your Mac's recommended wattage in System Information > Power. If the charger is rated lower than your Mac needs under load, it isn't broken — it's just undersized, and your Mac will charge slowly or not at all while in heavy use.
Why does my Mac charge slowly even with the original Apple charger?
The original charger can still charge slowly if it's being shared across multiple ports on a multi-port charger, if the cable between the charger and Mac is underrated, if Optimized Battery Charging is intentionally holding charge below 100%, or if the battery itself has degraded and can no longer accept a fast charge rate.
See also: Is My Mac Getting Enough Power From My Charger? (Decision Tree)