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Door staff@engadget.com (Gabriela Vătu) - 23 Aug 2026
The answer to this question really depends on your phone's fast-charging capabilities. If your phone supports higher-voltage charging and the laptop charger can deliver it, then yes, you'll likely see faster charging speeds than with a standard wall adapter. For example, Apple states that fast charging for many recent iPhones requires a compatible 20W or higher USB-C power adapter. A 65W laptop charger clears that bar quite easily, so your iPhone will negotiate the power it needs and charge accordingly. You should also be aware that some smartphone brands use their own proprietary charging protocols that require their specific cable or power brick to achieve advertised speeds.
However, if your phone is limited to 18W or 20W input, plugging it into a 100W laptop charger won't make it charge any faster, as the phone will only pull what it's rated for. More watts on the charger label doesn't mean more speed; it just means the charger has headroom for other devices. Since you'll most often see 100W, 140W or higher on multi-port chargers, those maximum outputs are designed to "cover" all plugged-in devices. The reverse, namely using your phone's charger with your laptop, won't deliver the same quick charge you are used to achieving. Oh, and you shouldn't expect impressive results if you use your car's USB ports to charge your laptop, either.
You should still exercise caution when charging your devices, especially if you have cheap, uncertified chargers. Counterfeit or poorly engineered chargers often bypass essential isolation barriers between the AC mains and the DC output side, so a surge in that type of device can pass damaging voltage spikes to your phone. Low-quality cables are also a hidden risk, as a non-certified USB-C cable may lack the internal pull-up resistor required by the USB-C spec. As a rule of thumb, before you use any charger, check it for safety certification markings such as Underwriters Laboratories (UL), Intertek (ETL) or the CE mark.
Since we've focused on whether or not it's a good idea to charge your smartphone with your laptop brick, you should know that other smaller USB-C devices may not come with the same microcontrollers needed to properly communicate with a high-power charger. Most fast chargers start at 5V and only step up after negotiation, so the risk is usually low, but you should still stick to the charger that came in the box, just in case.
However, if your phone is limited to 18W or 20W input, plugging it into a 100W laptop charger won't make it charge any faster, as the phone will only pull what it's rated for. More watts on the charger label doesn't mean more speed; it just means the charger has headroom for other devices. Since you'll most often see 100W, 140W or higher on multi-port chargers, those maximum outputs are designed to "cover" all plugged-in devices. The reverse, namely using your phone's charger with your laptop, won't deliver the same quick charge you are used to achieving. Oh, and you shouldn't expect impressive results if you use your car's USB ports to charge your laptop, either.
You should still exercise caution when charging your devices, especially if you have cheap, uncertified chargers. Counterfeit or poorly engineered chargers often bypass essential isolation barriers between the AC mains and the DC output side, so a surge in that type of device can pass damaging voltage spikes to your phone. Low-quality cables are also a hidden risk, as a non-certified USB-C cable may lack the internal pull-up resistor required by the USB-C spec. As a rule of thumb, before you use any charger, check it for safety certification markings such as Underwriters Laboratories (UL), Intertek (ETL) or the CE mark.
Since we've focused on whether or not it's a good idea to charge your smartphone with your laptop brick, you should know that other smaller USB-C devices may not come with the same microcontrollers needed to properly communicate with a high-power charger. Most fast chargers start at 5V and only step up after negotiation, so the risk is usually low, but you should still stick to the charger that came in the box, just in case.