Many phones now ship with only a cable in the box, so buying a charger has become a routine purchase. The choice looks simple, a plug and a cable, but it determines how fast a phone charges, whether one charger can also serve a tablet or laptop, and, with poorly made products, whether it is safe to leave plugged in. This guide explains the specifications that matter for wall chargers, cables and wireless chargers, drawing on Apple’s guidance on power adapters, the USB Implementers Forum (USB-IF) standards for USB Power Delivery and USB-C, the Wireless Power Consortium (WPC) for Qi wireless charging, and battery safety advice from the National Fire Protection Association (NFPA). It explains features rather than recommending products.

In short: buy a charger that meets recognized safety standards, with a USB-C port supporting USB Power Delivery at a wattage your phone can use; pair it with a cable rated for that power; and for wireless charging, look for Qi certification.

Wall chargers: wattage and USB Power Delivery

A charger’s wattage is the most visible number, but a phone only draws what it can accept. USB Power Delivery (USB PD), defined by USB-IF, lets the charger and phone negotiate a suitable power level, and USB-IF notes that it allows each device to take only the power it requires. That is why a higher-wattage USB PD charger can safely charge a phone that accepts less; the phone simply negotiates a lower level.

Points to check:

  • What your phone supports. Manufacturers list compatible fast-charging standards and wattage. Apple’s power adapter overview, for example, lists which adapters came with which models and notes that its 18 W USB-C adapter can fast charge iPhone 8 or later.
  • Port type. USB PD charging uses USB-C. USB-A ports on older chargers still work with suitable cables but generally do not provide USB PD.
  • Multi-port chargers. Total output is often shared between ports, so each port may provide less when several devices charge.
  • Input voltage. Apple’s adapters are designed for 100 to 240 V AC, 50 to 60 Hz, which helps when travelling. Check your charger’s label before using it abroad.

More on wall chargers is in phone chargers.

Safety standards and third-party chargers

Apple’s guidance is a useful benchmark for any brand. It says its power adapters are designed to meet government safety standards, and that in the United States and many other countries the relevant standards are IEC/UL 60950-1 or IEC 62368-1. You can charge with “Made for iPhone” or other third-party cables and power adapters that comply with applicable regulations and safety standards, but Apple warns that other adapters might not meet those standards and that charging with them could pose a risk of death or injury.

NFPA’s battery safety advice makes the same point from the fire-safety side: buy products listed by a nationally recognized testing laboratory and labeled accordingly, and use charging equipment that is compatible with your device. Fire services also warn about counterfeit chargers; Shropshire Fire and Rescue Service in the UK lists signs such as missing markings or spelling errors, a hollow feel and unusually light weight, because fakes contain few of the components needed for safety. Practical signs of a charger to avoid:

  • No certification or listing marks, or misspelled brand names and markings.
  • Unusually light weight or a hollow-feeling housing.
  • A price or listing that looks too good for a brand-name product sold by an unknown seller.
  • Damage: bent or loose prongs, a cracked case or a frayed cable.

Cables: power rating and data speed

Cables are not interchangeable even when the plugs look the same. USB-IF’s USB-C guidelines describe several points worth knowing:

  • A USB 2.0 Type-C cable supports only USB 2.0 data (up to 480 Mbps) but can support USB Power Delivery. That is fine for charging, slower for file transfer.
  • Full-featured USB-C cables carry higher-speed data and display signals as well as power.
  • USB-IF explains that USB PD originally topped out at 100 W using cables rated at 5 A, and its Revision 3.1 update defined cables for up to 240 W. For phones, almost any well-made cable rated for at least the charger’s output is enough; laptops need cables rated for their higher wattage.

Apple notes that recent iPhones ship with a USB-C cable that supports fast charging and works with USB-C power adapters and computer ports. Replace any cable that is frayed or has a damaged plug. Cable types are compared in charging cables.

Wireless chargers and Qi certification

Wireless charging uses a pad or stand instead of a cable. The Wireless Power Consortium, which develops the Qi standard, describes its standards as intended to make wireless power devices safe, interoperable and efficient, and its certification lets products display the Qi logo. It also offers a database to check whether a product is Qi certified. The WPC introduced Qi2, with magnetic alignment, in 2023, and a higher-power Qi2 25W version followed.

When choosing a wireless charger:

  • Confirm the product is Qi or Qi2 certified in the WPC database, not just described as “Qi-compatible”.
  • Check which wattage your phone supports wirelessly; it may differ from its wired rate.
  • Use the power adapter the wireless charger specifies; an underpowered adapter slows charging.

See wireless charging.

Charging habits that reduce risk

NFPA’s advice for lithium-ion devices applies to every phone:

  • Stop using a device whose battery shows signs of damage, such as an unusual odor, excessive heat, popping sounds, swelling or a change in color.
  • Do not store or charge devices in extremely hot or cold places.
  • Have repairs carried out by a qualified professional.
  • Do not throw lithium-ion devices in household trash or recycling; use a battery recycling or hazardous waste collection point.

Charge on a hard, stable surface rather than a bed or sofa, where heat cannot escape.

Other mobile accessories

Car mounts and in-car chargers are covered in car phone accessories, and stands in phone stands. For portable charging away from an outlet, see our guide to choosing a power bank under travel gadgets. All mobile guides are collected under mobile accessories.

Sources