The next time you charge up your smartphone, take a look at the tiny symbols on the adapter. There are probably enough of them to make a NASCAR car jealous. And they all refer to specifications meant to keep you and your phone safe. After all, a lot can happen in electronic circuitry placed between you and a wall outlet, including fires.

Chances are you won't have to worry about such dramatic experiences if you're using the smartphone charger that came with your device or bought it from a well-known company such as Apple or Samsung. And there shouldn't be anything wrong in saving a buck by bringing home a lesser-known brand, provided it has the official markings of a safe product.  

Two significant symbols to look for come from Underwriters Laboratories (UL) and Intertek (formerly Electrical Testing Laboratories, or ETL). Both are independent safety consulting and certification organizations affiliated with Nationally Recognized Testing Laboratory (NRTL) program of the Occupational Safety & Health Administration (OSHA).

Six common symbols you should find on your smartphone's charger

These organizations have two core jobs. They check performance claims, such as whether a smartphone charger or other product outputs power at the promised voltage and amperage. More critically, they test electrical devices as well as the cables and accessories that feed them to make sure they comply with OSHA’s safety requirements. 

“We attach tiny heat sensors called thermal couplers to significant points of resistance on the circuit board to make sure the product charger doesn’t overheat, [and] check the materials it’s made from to insure they’re sufficiently fire-resistant,” says John P. Drengenberg, UL’s consumer safety director. Testers also measure the thickness of the enclosure and other components to make sure nothing would prevent the product from being used properly, possibly adding a fire danger.

The symbol for UL is a circle with a misaligned “U” and L” inside it (see above). For Intertek, it’s the initial of the company's old name, ETL, surrounded by a circle. Both groups keep a vigilant lookout for counterfeiting and logo placement. Occasionally, a logo might seem to imply that an entire product has been certified, when in fact the label applies to just one component, such as the battery. (Such potential confusion led to a conflict between UL and hoverboard makers this past winter.)

One difference between the two organizations is that UL also develops testing standards, while ETL follows those standards along with standards established by other organizations.

Other Symbols

CE. This stands for the French phrase "Conformité Européene" which means "European Conformity." This logo, which is found on products that might be sold in the approximately 30 countries participating in the European Union marketplace, is not so much a certification as a declaration by the manufacturer that the product meets relevant European health, safety, and environmental protection legislation, as spelled out in each country’s Product Directives. Having that symbol allows a product to be sold with less red tape within the EU.

CE compliance isn't confirmed by independent labs, but regional authorities can revoke a company’s right to display the symbol, as well as issue fines and other penalties if a product doesn't conform to the standards.

100-240V—50-60 Hz. Lots of people take a smartphone charger abroad. This language indicates that the charger can be plugged into a 240V European outlet without a voltage converter and live to tell about. One thing a U.S. traveler will need: A passive adapter that allows you to plug your charger to the different-shaped holes of a foreign wall outlet.  

Trash can with an X over it. This refers to the EU’s Waste Electrical and Electronic Equipment (WEEE) Product Directive, mandating that the device be recycled or disposed of in a responsible way because of the environmentally detrimental materials it contains.

Square within a square. This indicates that the device is double insulated, usually with an outer cover. This may minimize the risk of electric shock.  

A little house (sometimes with an arrow). The icon means that the product is meant to be operated indoors only, not where it would be exposed to the weather.

A rectangle with lines coming out at each end. This shows that the product is protected by a fuse or circuit breaker. This feature is most important in devices that draw a lot of current, such as hair dryers.

Closeup of a smartphone charging adapters from HTC (left) and Samsung (right), each adorned with more than a dozen certification symbols
Charging adapters are brimming with a variety of logos attesting to their safety and performance, and even provide guidance for disposal.

How to Spot a Counterfeit Charger

  1. Look for typos. Companies serious about meeting standards are equally serious about labeling—and counterfeiters can be comically bad at proofreading. According to Drengenberg, some of them even manage to spell "UL" with a "V." Other things counterfeiters miss when they’re faking a UL symbol: The tiny “US” that should appear next to it for products approved for use in America.
  2. Beware of rock-bottom prices. If the price seems too good to be true, maybe it is. You’ll find USB or Lightning phone chargers on eBay for as little as a $1.50, or three for $4. Skip ‘em. However, you don't have to pay a lot: You can find safe bets for about $10. Online retailers, such as Amazon, often provide product views that will let you see the certification logos. In any case, make sure you can return a product if it doesn’t meet the standards. 
  3. Who made this? Sometimes a company peddling a shoddy charger will get the logos right but leave out one important thing: its own name. The reason is simple. If something goes wrong, they don’t want anyone to come looking for them. We strongly suggest you don’t buy a product without a manufacturer's own logo.