Imagine stumbling upon secret codes buried deep in your smartphone that can unveil hidden features, but what if these digital backdoors raise eyebrows about security and privacy? It's a tantalizing mystery that has intrigued tech enthusiasts for decades, and it's still alive and kicking in our modern mobile world. Stick around— we're about to dive into how these codes work and why they might just change the way you view your phone.
For as long as personal computers have been around, programmers have enjoyed adding hidden 'back doors' or playful Easter eggs into software, accessible only with special keys. This tradition didn't fade with the rise of mobile devices; in fact, it evolved. Excitingly, many of these aren't just for developers—you can access some yourself through Unstructured Supplementary Service Data, or USSD for short (often called 'quick codes' or 'feature codes'). Think of USSD as an extra layer beyond your phone's usual interface, designed to tap into behind-the-scenes features. It started back in the days of GSM phones, but it's still powering many 4G and 5G devices today. Then there are Man Machine Interface (MMI) codes, which manufacturers create specifically for their own products.
These public codes—some estimates say there are over 800—let you chat directly with your carrier's systems and unlock backend functions on your device. To use them, simply type the code into your phone's dialer (that's the screen for making calls) and press call. They typically start and end with * or #, sandwiched around a string of numbers. This setup makes accidental dialing nearly impossible, keeping things intentional.
But here's where it gets controversial... Are these codes empowering users, or do they inadvertently expose vulnerabilities that carriers might not want us poking around? While they're not always super useful, they can reveal mundane details like cell tower performance or your device's IMEI number (we'll explain that shortly). Still, exploring them can feel like a fun adventure, uncovering unexpected capabilities under your phone's surface. Just a gentle warning: tread lightly. Some codes, especially those involving 'wipe' functions, could harm your phone—don't factory reset just for kicks.
And this is the part most people miss... Providing a universal list of these codes would be pointless. They often vary by carrier, operating system, or even phone model within the same brand. Plus, carriers frequently disable or update them to prevent everyday users from accessing them. If you're curious, search online for your phone's make, model, and carrier combined with 'USSD' or 'MMI' to find tailored lists. Expect some to be outdated—we tested a bunch on an iPhone 15 Pro with AT&T, plus Motorola and Samsung devices, and only these worked on at least one. Enjoy responsibly!
Field Mode: *3001#12345#*
Enter this into your dialer and hit call to enter 'Field Mode.' It provides insights into nearby networks, cell towers, and signal strength. Note that this won't detect if your phone is being tapped—that's more myth than reality. Most data is technical jargon for pros only. For a quick boost, check out tips on improving signal strength.
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IMEI Display: *#06#*
This pulls up your International Mobile Equipment Identity (IMEI) number, unique to your device and tied to its network. It's handy for blacklisting stolen phones or getting support. With dual SIM, eSIM, or multiple cards, you might see more than one. On iPhone, Settings > General > About works too, but this code is cross-platform and speedy for techs.
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Call Forwarding: *#67# and *#21#*
Use these to check where calls forward when you're busy or unavailable.
*#67# often shows your carrier's voicemail (like AT&T's Voicemail Call Center), but you can redirect to another number, such as home or office. On iPhone, adjust in Settings > Phone > Call Forwarding; Android varies—open Phone app > menu > Settings > Calling accounts > select SIM > find call forwarding. This reroutes calls from default voicemail, potentially to another with messaging.
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Call Waiting: 43 (Various Combinations)
Call waiting alerts you to incoming calls during a chat.
On AT&T, *#43# might disable multiple waitings (voice, data, etc.), reactivate with the same code, confirm in Settings. T-Mobile uses similar. Verizon's *43 deactivates forwarding (not waiting), with *42 to enable; *70 before a number pauses it temporarily.
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Available Minutes: 646*
'646' spells 'MIN' on the keypad. On AT&T iPhone or Android, it sends an SMS with remaining minutes. AT&T suggests *646# for rollover; *876# for Spanish. Verizon uses #646; T-Mobile #646#.
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Billing Cycle: 3282*
This triggers an SMS with billing details, like cycle start, usage (per line if multiple), and overage warnings. '3282' spells 'DATA.' AT&T: *3282#, Verizon: #3282, T-Mobile: #932#.
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Caller ID: #31#*
This disables Caller ID (or CND). To enable, use *31# or Settings > Phone on iPhone.
It's also for per-call blocking: #31# (or *67) before a number, e.g., #31#1234567890. Handy on landlines. If always off, *82 before a number reactivates for one call.
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Test Alert Status: 500525371#*
Check if your phone receives government test alerts. Dial to confirm; 500525370# to disable.
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Check Account Balance: *777# (Prepaid) or *225# (Contract)*
Prepaid: *777# sends a text with remaining balance; contract: *225# for due amount. AT&T: *225#, Verizon: #225, T-Mobile: #225#.
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Android Phone Stats: ##4636#*#*
Opens a testing panel with 4G/5G info, phone details, usage, Wi-Fi, NFC.
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Call Barring: *#33#*
Blocks all calls (in/out). Check status with *#33#; enable with *33[SIM-PIN]# (deactivate same way). Options for specific calls like international. Easier to block per number—see guides for iPhone/Android.
(Credit: Apple/PCMag)
Read the Regulations: *#07#*
Directs to legal info, warranties, RF warnings. iPhone: Settings > General > Legal & Regulatory.
(Credit: PCMag)
Wipe Your Android Device: 27673855#*
Untested by us—reportedly factory resets Android, reinstalling firmware. Proceed cautiously!
The Information You Need: N11 Codes*
In the US, N11 codes (digit + 11) provide audible info:
211: Community services like utilities, housing.
311: Local government help, e.g., trash schedules, potholes.
411: Directory assistance (fees possible; online search better).
511: Traffic updates.
611: Carrier customer service.
711: Services for the deaf.
811: Utility line checks before digging.
911: Emergencies.
Do you think these hidden codes empower users or pose risks we shouldn't ignore? Is exploring them a harmless hobby, or could it lead to unintended privacy breaches? Share your thoughts in the comments—do you agree carriers should keep them locked down, or disagree that they're a fun feature worth more openness? We'd love to hear counterpoints or even controversial takes on whether tech giants are hiding too much from us on purpose.
Evan Dashevsky contributed to this story.
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Eric Griffith
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I've been crafting stories about tech since 1992, over half that time at PCMag. I joined as a senior writer during PC Magazine's print era, later managing business coverage before returning to features. I pen pieces on all tech topics, plus oversee special projects like Readers' Choice and Business Choice surveys, annual Best ISPs and Gaming ISPs, Best Products of the Year, and Best Brands (including for tech support, longevity, reliability).
My journey began post-college, editing hardware and dev tools, then shifting to software, family tech, and Wi-Fi. I helped launch magazines like Windows Sources, FamilyPC, Access Internet Magazine (all gone, not my doing). Freelanced for outlets from Sony Style to Playboy.com, Flux. Degree in TV/Radio from Ithaca College, with writing minor.
In spare moments, I wrote novels like BETA TEST (a lighthearted apocalypse per Publishers' Weekly) and YA tale KALI: THE GHOSTING OF SEPULCHER BAY—grab them on Kindle.
Working remotely from Ithaca, NY, pre-pandemic.
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Iyaz Akhtar
Mobile Writer
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Tech has been my passion forever. As PCMag's mobile writer, I test latest phones/tablets, ensuring accurate buying advice through rigorous checks— after all, your device is personal. Two decades in tech journalism, with bylines at The Apple Blog, PCMag, This Week in Tech, CNET. Also produce videos like This Old Nerd for practical tech tips.
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