Technology advice travels fast and rarely carries its evidence with it. A tip that was accurate for one generation of hardware gets repeated long after the hardware changed, and a rule that is only partly right gets simplified into an absolute. The result is a folklore of device habits that many people follow without knowing where they came from.
Five widely repeated beliefs are worth checking here, each against a source that can actually support a claim. In several cases the myth is not entirely false, and the useful answer is a matter of degree.
Myth 1: Private Browsing Makes You Anonymous
Private or incognito windows are often described as a way to browse invisibly. What they do is narrower. According to Mozilla's own explanation of its private mode, the feature keeps your browsing history private on that device and clears cookie data when the window closes. It also blocks some tracking by default in that browser.
The same page lists what private browsing does not do. It does not stop your internet service provider from seeing where you go online. It does not hide your physical location from websites, and it does not protect you from viruses or malware. Activity may still be visible to an employer or a school if you use their network, and if you sign into an account during a private session, that activity can be saved to the account. A 2018 study by Carnegie Mellon University researchers found that private browsing does keep activity from being revealed to other users of the same computer, but that people overestimate the protection it gives against online tracking and targeted advertising.
The logic is straightforward. Your request has to travel across a network to reach a website, and each party along the path can observe what it needs to deliver the page. Private mode changes what your browser remembers afterward, not what the network carries. It is useful for keeping a shared computer tidy, checking something without personalizing recommendations, or logging into a second account temporarily. It is not a shield.
Myth 2: Charging Overnight Ruins a Battery
The fear behind this belief comes from an older era. Some older rechargeable designs could be harmed by careless charging, and people assumed the same about phones. Modern devices use lithium-ion cells managed by a charging controller, and the charging circuitry is built to stop delivering full current as the cell nears full.
The real story is about aging. Apple's guidance notes that built-in systems manage charging patterns and battery temperature to reduce aging, and that features such as optimized charging can delay reaching a full charge until it is needed. The company also warns that exposure to ambient temperatures above about 35 degrees Celsius (95 degrees Fahrenheit) can permanently damage battery capacity, and it advises removing a case during charging if the device gets hot. For long-term storage, it recommends leaving the device at roughly half charge rather than completely full or completely empty.
So the useful summary is different from the myth. A night on the charger is not a hazard in itself. Heat is the factor Apple singles out as able to cause permanent capacity loss, and the existence of features that defer a full charge suggests that time spent at 100 percent also matters. If you want to understand why a lithium-ion cell behaves this way, How Rechargeable Batteries Store Energy explains the chemistry, and What Happens During Fast Charging covers the heat question.
Myth 3: Phone Radiation Causes Cancer
Phones communicate using radio waves, a form of non-ionizing radiation. The National Cancer Institute explains that this radiation has low energy and, unlike X-rays or radon, cannot damage DNA directly. The distinction matters because the mechanism by which ionizing radiation raises cancer risk depends on that kind of damage.
The institute also summarizes epidemiological evidence. Rates of brain cancer stayed stable in several countries during years when cell phone use grew enormously, and large studies such as Interphone, the Danish cohort, the Million Women study, and COSMOS have not found clear associations. Studies of children have also not detected increased brain tumor risk.
The full picture includes a caution. The International Agency for Research on Cancer classified radiofrequency fields as "possibly carcinogenic to humans" in 2011, a category that reflects limited evidence and does not mean a proven cause. Research methods have limits, such as reliance on people's memory of their phone use, so scientists continue to monitor results. The accurate statement is that the evidence to date does not show that phones cause cancer, and the physics gives no known pathway for direct DNA damage.
Myth 4: Unused Memory Is Good and Full Memory Is Bad
Many people open a task manager, see that most of their computer's RAM is "in use," and conclude that something is wrong. Yet memory that holds nothing useful provides no benefit. Operating systems deliberately use spare RAM to keep recently used files and program data close at hand, so that reopening them is fast.
The Linux kernel documentation describes the principle: whenever a file is read, its data is put into the page cache to avoid expensive disk access on later reads, and pages that can be freed at any time because the same data exists elsewhere, such as on a disk, are called reclaimable. In other words, a large cache figure is a sign that the system is using its memory to save work, not a sign that memory has run out. Other operating systems use the same idea under different names.
The number that matters is how much memory is available on demand and whether the system is being forced to write data out to disk constantly. Long-term storage, from the floppies behind Why the Save Icon Is a Floppy Disk to modern drives, is much slower than RAM, which is why caching in RAM helps. Utilities that promise to "free" memory by discarding this cache typically make the next application launch slower, because the data has to be read again.
Myth 5: More Megapixels Means a Better Camera
Megapixels count how many picture elements a sensor has. A camera advertised with more of them sounds sharper, but the count is only one variable. Each pixel is a tiny well that collects light. On a sensor of fixed size, adding pixels makes each one smaller, and a smaller well collects fewer photons.
Researchers at Stanford University studied this trade-off in a 2006 paper on pixel size, using simulations of sensors with the same chip area but different pixel sizes. They found that reducing pixel size increases spatial resolution but comes at a cost in light sensitivity, and that without compensating technology smaller pixels bring lower dynamic range, weaker low-light response, and a higher dark signal. The paper also notes that engineering advances in mobile sensors have offset much of the expected loss.
That last point is important. A modern high-resolution sensor can produce excellent images, and the megapixel count does affect how much you can crop or enlarge a photo. The myth is the assumption that the number alone predicts quality. Lens quality, sensor size, image processing, and lighting typically matter as much or more. For a deeper look at what happens on the sensor, see the article on how digital camera sensors capture images.
What These Myths Have in Common
Each of these beliefs is a shortcut that fits a simple story. Private mode sounds like a disguise, overnight charging sounds like overfeeding, radiation sounds like danger, full memory sounds like clutter, and more megapixels sounds like more detail. The shortcut works because it is easy to remember, not because it is a good description of the mechanism.
A quick test helps. Ask what physical or logical process would produce the claimed effect, and whether a reliable source describes that process. Where the answer is unclear, treat a tip as a rule of thumb rather than a law. The same habit applies to security features, as the explanation in How Biometric Scanners Work shows: every system involves trade-offs that a one-line claim hides.
In Short
Private browsing controls what your own browser remembers, not what networks and websites can see. Overnight charging is not the danger it is often made out to be, while heat and long periods at full charge are the real drivers of battery wear. Current evidence does not show that phone radio waves cause cancer. Memory that a computer uses as cache is working for you, and megapixels alone do not decide image quality. Checking a claim against a source that explains the mechanism usually settles which part of a belief is true.
