I spent a week punching secret dialer codes into an iPhone and a handful of Android phones. Fourteen of them reliably surfaced hidden menus or deep carrier controls that most people never see. Some are practical—think network diagnostics and call forwarding checks—while a few feel like peeking behind the curtain of how cellular systems actually work.
What worked on both phones
Start with the universal: enter *#06# to instantly display the device’s IMEI and, on eSIM-capable models, the EID. Carriers use these identifiers to unlock phones, and the CTIA’s stolen phone database leverages the IMEI to help block lost or stolen devices from being reactivated. GSMA estimates hundreds of carriers participate in global IMEI blacklisting, making this code essential if you ever need to file a theft report or check warranty status.
GSM service codes can quietly confirm if your calls are being redirected. *#21# shows whether unconditional call forwarding is active, *#62# checks forwarding when your phone is unreachable, and *#67# does the same when the line is busy. If you discover forwarding you didn’t intend, dialing ##002# cancels all types in one shot. These worked on multiple carrier SIMs, though CDMA-legacy networks and some prepaid plans may block them.
Curious about your caller ID behavior? *#31# returns the status of CLIR (the setting that hides or shows your number). It’s a quick sanity check if friends say your calls show up as “Unknown.” If a code returns an error, your carrier likely restricts that function on your plan.
iPhone-only: field test, alerts, and message center
Apple hides a full network dashboard behind *3001#12345#*. That launches Field Test Mode, where signal readouts switch from bars to engineering-grade measurements like RSRP and RSRQ. It’s the view carrier engineers use to evaluate coverage. If you’ve ever suspected your signal “bars” were misleading, this menu tells the truth in numbers.
Dial *#07# on an iPhone to pull up regulatory and certification info tied to your specific model. It’s not flashy, but it’s useful when selling a device or verifying exact hardware revisions without digging through the About screen.
Two little-known service codes govern federal test alerts on many iPhones. *#5005*25371# checks whether the device is set to receive test alerts from emergency services; *5005*25370# turns that test mode off. The Federal Communications Commission oversees the Wireless Emergency Alerts system, and carriers regularly conduct controlled tests—these codes let you verify your participation without sifting through settings.
For SMS diagnostics, *#5005*7672# queries your device’s SMSC (Short Message Service Center) address. Carriers route texts through that server. In rare cases of outgoing messages failing, technicians use the SMSC to troubleshoot route issues.
Android and manufacturer service menus
On stock and near‑stock Android builds, *#*#4636#*#* launches the Testing menu. Expect pages for Phone information (radio, network type, and cell connection stats), Usage statistics, and Wi‑Fi information. It’s the fastest way to confirm your device is locked onto LTE, NR (5G), or dropping back to older standards, and to check whether VoLTE is registered on your SIM.
Samsung hides two powerful tools. *#0*# opens a hardware diagnostic suite with panels for display colors, touch sensors, vibration, camera checks, and more. It’s ideal before reselling a phone or after a drop to confirm everything still works. *#9900# opens SysDump, which surfaces logs and a storage cleanup (“Delete dumpstate/logcat”) that can free space if crash logs balloon. These menus are intended for service centers, so change only what you understand.
Real-world uses for these 14 codes
Traveling abroad and switching to an eSIM? Between *#06# (for EID) and the 4636 Testing panel (to see if you’re on the right bands), you can confirm activation and roaming at the airport gate. GSMA reports that hundreds of mobile operators now support eSIM profiles across dozens of markets, but roaming behavior still varies by partner network—these menus show the honest state of your connection.
If calls are skipping voicemail or ringing forever, the forwarding codes (*#21#, *#62#, *#67#, and ##002#) reveal or reset misconfigurations that sometimes happen when you swap SIMs or port a number. For iPhone users in broadcast-heavy areas, the test alert check (*#5005*25371# and *5005*25370#) clarifies whether you’ll receive non-consumer test notifications during maintenance windows.
Safety, carrier caveats, and why these menus exist
Most codes only query status or open read‑only dashboards. Still, be cautious: some manufacturer codes can alter system files or, on older models, trigger resets. Service centers and field technicians rely on these backdoors for diagnostics, provisioning, and regulatory compliance testing—regular users aren’t the primary audience, which explains the sparse documentation.
Carrier behavior matters. On some networks, GSM service codes are intercepted and processed server‑side; on others, they’re blocked or mapped to app-based settings. If a code returns “Error” but the corresponding toggle exists in your Phone settings, use the settings path instead.
If something goes wrong
Write down your baseline before changing anything, especially in Samsung’s SysDump or Android’s Testing menu. If you accidentally enable a network option and can’t reverse it, power-cycle the phone, reseat the SIM, or reset network settings. For forwarding and caller ID issues, re‑enter the cancel codes (##002#, or query with *#21# and *#31#) to restore defaults. When in doubt, back up and consult your carrier’s support—especially for provisioning tasks tied to your account.
Used carefully, these 14 codes turn your phone into its own service toolkit. They won’t replace a carrier engineer—but they give you the same clear view of what your device is doing on the network, minus the guesswork.