How to compare USB-C cables on a MacBook

Your MacBook may charge quickly with one cable and slowly with another, or the rate may change during the same charge. Battery level, heat, and apps running in the background can all affect the result. A quick comparison under different conditions can make a good cable look faulty.

Use the Charger & Cable Test to compare the reported charge rate over repeated tests. It measures battery percentage change per minute, not the cable's electrical wattage, so consistency matters more than one reading.

Compare the cables under the same conditions

1. Open the Charger & Cable Test on the MacBook. Check that it reports battery and charging information. If it does not, try another browser that reports battery data. A missing reading is a browser limitation, not proof that the cable is bad.
2. Unplug the MacBook and note its battery percentage. Start each cable test at roughly the same level, preferably well below 80 percent. Charging can slow near a full battery, and macOS may pause or limit charging for battery management.
3. Use the same wall adapter, outlet, MacBook charging port, and setup for every cable. Disconnect docks and hubs so you are testing the cable, not another part of the connection.
4. Connect cable A and note the reported charge rate. Keep the MacBook awake for the same length of time for each run, such as 10 minutes. Write down the starting percentage, ending percentage, and rate.
5. Unplug cable A, let the computer return to a similar state if needed, then repeat with cable B. Keep the screen brightness and open apps about the same, and avoid downloads, video calls, or other heavy tasks.
6. Repeat the comparison at least once. If you have time, test in an A, B, B, A order. This helps show whether a difference follows the cable or simply reflects the battery getting warmer or fuller.

Use comparable USB-C charging cables for this test. If you switch between USB-C and MagSafe, you are comparing more than the cable, including the charging connection and possibly the adapter. Keep those tests separate.

What the result means

The cables show similar rates

If the rates are close across repeated runs, the test has not found a clear charging difference in those conditions. It does not prove that both cables support every data speed or charging feature. It only compares the battery's reported charging rate during your test.

One cable is consistently slower

A repeated difference suggests that cable, its connectors, or its charging capability may be limiting the result. Check the cable's specifications and condition, then test it again with the same adapter and port. The MacBook and adapter also set limits, so a cable with a higher rating cannot make the computer charge beyond its supported rate.

Both cables are slow

The adapter, outlet, MacBook port, battery level, temperature, or background workload may be the limiting factor. Try a known-compatible wall adapter and a different outlet, while keeping the rest of the comparison unchanged.

The rate changes a lot during a test

Charge rate is not constant. It can fall as the battery fills, and macOS may manage charging based on temperature and battery settings. Do not treat a single brief dip as a cable failure. Compare similar time windows and starting percentages instead.

The test shows no battery or charging data

Some browsers do not provide the battery information the test needs. Try another browser on the MacBook. If the browser still cannot report it, use macOS's battery indicator to confirm whether the Mac is charging, but do not assume that the missing browser reading means the cable is faulty.

How to get a fairer comparison

1. Keep the adapter and outlet fixed. Change only the cable. A different power adapter, port, or wall outlet can change the result and make it impossible to isolate the cable.
2. Test at a similar battery level. A MacBook may charge at different rates at 25 percent and 85 percent. Start each run at a similar percentage and avoid testing close to full.
3. Keep the MacBook cool and idle. Close demanding apps and let the computer cool if it is warm. High workload or temperature can affect charging behavior, so do not compare a cool, idle run with one made during a video call.
4. Check charging management. In macOS, open System Settings › Battery and review the battery status and charging options. Optimized charging may delay charging or hold the level below full. Note what it is doing and compare cables under the same conditions.
5. Inspect the connectors. Look for bent contacts, debris, fraying, or a loose fit. Do not force a connector into the port. If it becomes unusually hot, disconnect it and stop using that cable.
6. Test the cables in reverse order. Repeat the comparison with the other cable first. If the same cable remains slower in multiple runs, the result is more useful than a difference seen once.
7. Check the MacBook's battery condition. Open System Settings › Battery › Battery Health and review the reported condition. If macOS recommends service, or every cable and adapter behaves poorly, the issue may not be the cable.

When the cable or MacBook may need attention

Replace a cable that is visibly damaged, repeatedly disconnects when gently moved, or remains much slower across controlled tests with compatible equipment. Do not keep using a cable or connector that becomes unusually hot. If several known-good cables and adapters all charge slowly or disconnect from the same MacBook port, contact Apple support or a repair shop to check the port and battery.

Why percentage per minute is only a comparison

A battery percentage is a rounded estimate of stored charge, not a direct power measurement. The test's percent-per-minute figure can help compare runs on the same MacBook, but it cannot tell you the exact watts delivered by a cable. It also cannot prove that a cable supports fast data transfer. For a useful comparison, look for a difference that repeats with the same adapter, battery level, port, and workload.