An app's listed size only covers the program binary. The cache and documents layer beneath it, which both Android and iOS wall off from automatic deletion, is where most of a full phone's storage actually lives.

Wireless charging is roughly 70-80% efficient versus 95% for a cable, and the lost energy shows up as heat -- normal, and rarely something to worry about.

A smoke alarm's test button only confirms the horn and wiring work, not whether its ionization or photoelectric sensor can still detect real smoke after a decade of dust, grease, and radioactive decay.

There's no such thing as an "HDMI 2.1 cable" -- only a certified "Ultra High Speed" one, and the difference decides whether a TV blacks out at 120Hz.

Two chargers rated at the same wattage can still charge a phone at very different speeds, and the wattage number rarely explains why.

Inkjet printers periodically flush ink through their nozzles to stop them clogging — sending it straight into a hidden waste pad, whether or not you've printed a page.

A coffee stain or a peeling sticker shouldn't kill a QR code, and usually it doesn't. Here's the redundant-data trick, borrowed from deep-space communication, that keeps damaged codes readable.

SSDs need free blocks to write fast. The real reason a drive suddenly feels slow is almost always capacity, not calendar age.

Swapping the battery is supposed to end the chirping. When it doesn't, the real cause is almost always one of four things, and a dead battery usually isn't one of them.

Microwave ovens and Wi-Fi routers share almost the same frequency, and one of them is about 35,000 times more powerful than the other.

Six state laws took effect Jan. 1, pushing repair protections past a quarter of the country. But a software trick called parts pairing shows how much control manufacturers still keep.

A bulging phone case or a laptop trackpad that won't sit flat is usually the first visible sign of a chemical reaction inside a lithium-ion cell that started days or weeks earlier.