What secret codes are and how they work
Android secret codes are short sequences, mixing star, hash and digits, that you type into the phone's dialer to open hidden menus and information screens instead of placing a call. They are technically MMI (Man-Machine Interface) codes, a standard the phone intercepts before dialing, and they exist to give technicians and curious users quick access to diagnostics, hardware tests, and device information that is otherwise buried or unavailable. Type the code in the Phone app's dialer, and the corresponding screen opens instantly, no call, no app to install.
Their usefulness ranges from universal to brand-specific. A handful work on virtually every Android (the IMEI code above all), some open rich manufacturer test suites (Samsung's are famously comprehensive), and others vary or have been disabled entirely depending on the maker and Android version. This inconsistency is the main caveat: a code that opens a wonderful test menu on one phone may do nothing on another, because manufacturers choose which to support. Our secret codes tool lists the genuinely useful ones with descriptions and copy buttons, so you can try the ones most likely to work on your device.
Used sensibly, secret codes are a handy free diagnostic shortcut, checking your IMEI, glancing at signal strength in real numbers, or running a manufacturer's built-in hardware test. But a small number of codes trigger destructive actions like factory resets, so the golden rule is to know what a code does before you type it, and never enter a code you found without understanding it. This guide covers the safe, useful codes, flags the dangerous ones, and explains when a code is the right tool versus when our browser-based diagnostic tools do the job more reliably.
The universally useful codes
The one code that works on essentially every phone, and everyone should know, is the IMEI code: dial star-hash-zero-six-hash and your device's IMEI number(s) appear instantly. The IMEI is your phone's unique hardware identifier, and you need it to report a lost or stolen phone (so the carrier can blocklist the handset), to check a used phone's status before buying, and for insurance and warranty claims. Note it down somewhere safe now, our find-my-phone guide explains why having your IMEI recorded before a loss is so valuable, and this code is how you retrieve it.
The general test-and-info code that works on many (though not all) phones opens a phone-information screen showing battery status, usage statistics, and network details, useful for a quick look at signal strength in actual dBm numbers (far more precise than the bars) and battery information. Our no-signal guide uses this readout to turn 'bad coverage' into a measured value, and our battery-health guide notes it as one route to battery information. Availability varies, so treat it as a quick try; if it does nothing on your phone, the built-in settings or our tools provide the same data.
Beyond those, most genuinely useful codes are brand-specific hardware-test menus, covered next. But the pattern to internalize is that the safe, useful codes reveal information or open tests, they show you your IMEI, your signal, your battery, your hardware test suite. They do not change anything. The moment a code claims to reset, format, or wipe, it belongs in the danger category, and this information-versus-action distinction is the mental model that keeps code use safe.
Manufacturer test menus, especially Samsung's
The most rewarding secret codes open the manufacturer's built-in hardware test suite, and Samsung's is the gold standard. Dialing the Samsung test code opens a menu that runs individual tests for the screen (solid colors for dead pixels, touch grid), the speakers and receiver, the microphones, the sensors (gyroscope, accelerometer, proximity, light), vibration, the cameras, the buttons, connectivity, and more, essentially a factory diagnostic that lets you verify every component in a few minutes. It is invaluable when checking a used Samsung before buying, or diagnosing which component has failed on your own phone.
Other manufacturers have their own equivalents with their own codes, and some bury a hardware-test menu in Settings (often under a 'diagnostics' or device-care section) rather than behind a dialer code. The coverage and access vary widely: some brands offer rich test suites, others have removed dialer-code access entirely in favor of a settings menu or a companion app. Our secret codes tool lists the codes worth trying, and if your phone's maker has locked them, the built-in device-care diagnostics or our browser tools fill the gap.
This is exactly where our browser-based tools shine as the universal alternative, because they work on ANY phone regardless of brand or whether its secret codes survived. Our Dead Pixel Test, Touchscreen Test, Speaker Test, Microphone Test, Sensor Test, Camera Test and the rest replicate what a manufacturer's hidden menu does, with no code to remember and no brand dependency, run them from the browser on any Android and get the same component-by-component verdict. For checking a used phone of unknown brand, or when a maker disabled its codes, the browser tools are the reliable path, and our used-phone buying guide builds a full inspection around them.
The dangerous codes to know and avoid
A small number of secret codes trigger destructive actions, and the most important safety knowledge in this guide is to recognize and avoid them. Certain codes initiate a factory reset or wipe data immediately, sometimes with little or no confirmation, so a code copied from a random forum without understanding can erase your phone in one entry. Never type a code you cannot verify the purpose of, and be especially wary of any code presented as a 'fix' or 'secret trick' on untrustworthy sites, because tricking people into wiping their own phones (or worse) is a known scam vector.
The safe rule is the information-versus-action distinction from earlier: codes that DISPLAY things, IMEI, phone info, test menus, are safe to try; codes that claim to DO things, reset, format, wipe, restore, are the ones to avoid unless you have deliberately decided to factory reset and are using the proper method anyway (our factory-reset and Recovery guides). If you genuinely want to reset your phone, use Settings or Recovery Mode with a backup first, not a dialer code, because those methods give you the confirmations and safeguards a raw MMI code does not.
Our secret codes tool deliberately lists useful, safe codes and clearly flags any with destructive potential, so you can explore without landing on a data-wiping surprise. Treat any code from an untrusted source with the same suspicion our popup-ads and block-spam guides apply to too-good-to-be-true prompts: if a stranger on the internet urges you to type a mysterious code into your phone, that is a red flag, not a tip. Curiosity about your own device is healthy; typing unknown commands is not, and knowing which codes are safe (the informational ones) versus dangerous (the action ones) is the entire safety lesson.
When codes help, and the more reliable alternatives
Secret codes earn their place in a few specific situations. Checking your IMEI is genuinely best done with the universal code, it is instant and works everywhere. Glancing at real signal strength in dBm via the phone-info code is a nice precision upgrade over the bars when diagnosing coverage. And on a Samsung (or another brand with a working test suite), the hardware-test code is a fast, thorough component check, particularly when inspecting a used phone of that brand. For these, reach for the code.
But for most diagnostic needs, our browser-based tools are more reliable and universal than codes, precisely because they do not depend on the manufacturer having kept a code alive. Testing the screen, touch, speakers, microphone, sensors, camera, GPS, vibration or battery works identically on every Android through the browser, no code to remember, no brand lottery, and often with clearer, more interactive results than a terse factory menu. When you want to actually diagnose a component rather than just open a hidden screen, the tools in our tool categories are the dependable choice, and they are what our used-phone and component-specific guides build their inspections around.
So use secret codes for what they do best, your IMEI, a quick signal or battery readout, a brand test menu when it exists, and lean on the browser tools for thorough, universal component testing. Record your IMEI now (the one code everyone should run), keep our secret codes tool handy for the occasional useful code, and remember the safety rule that outlasts any specific code: information codes are safe, action codes are dangerous, and an unknown code from an untrusted source is never worth the risk to your data. That simple framework lets you enjoy the genuinely useful hidden features without ever falling into the destructive ones.