USSD and MMI codes are short sequences of stars, hashes, and numbers you type into your phone's dialer to reach hidden information, hardware tests, and carrier services. Many older lists circulating online are full of codes that newer phones no longer accept, so this guide focuses on what actually works in 2026 and tells you when a code is universal, manufacturer specific, or carrier specific.
Type each code exactly as shown, including every star and hash. Universal carrier codes run automatically once you finish typing, while most hardware and information codes need you to press the call button. Test responsibly and never run a reset code unless you have a current backup.
What USSD Codes Are
USSD stands for Unstructured Supplementary Service Data. These codes travel over your mobile network to your carrier's systems, which is why they work without Wi-Fi or mobile data and why the same code can behave differently from one carrier to another.
Carrier USSD codes handle account level tasks such as checking your balance, viewing call forwarding rules, and toggling caller ID. Because the network does the work, these codes generally behave the same on iPhone and Android.
What MMI Codes Are
MMI stands for Man Machine Interface. An MMI code is processed by the phone itself rather than the network, which is why most diagnostic and hardware test codes are MMI codes and why they vary so much by brand and model.
MMI codes usually open something on the device, such as a hardware test menu, a software version screen, or a sensor test. The same code on a different manufacturer's phone may do nothing or do something completely different, so treat brand specific codes as brand specific.
Universal Carrier Codes
These USSD codes are handled by the mobile network, so they work on both iPhone and Android as long as your carrier supports the feature. They are the safest codes to try because they only check or change call settings, never your data.
The syntax follows a pattern. Two stars activate a feature, two hashes turn it off, and a star followed by a hash checks the current status.
- *#06# - Show your phone's IMEI number
- *#21# - Check whether all calls are being forwarded
- *#61# - Check call forwarding for unanswered calls
- *#62# - Check call forwarding when your phone is unreachable
- *#67# - Check call forwarding when your line is busy
- ##002# - Cancel every call forwarding rule at once
- *#43# - Check call waiting status
- *43# - Turn call waiting on
- #43# - Turn call waiting off
- *#30# - Check whether you can see incoming caller IDs
- *#31# - Check whether your own number is shown on outgoing calls
- #31#number - Hide your number for a single outgoing call
Carrier Account Codes
Balance and usage codes are set by your carrier, not by Apple or your phone maker, so the exact code differs between providers. The examples below are common on some US carriers but are not guaranteed on yours.
If a balance code returns an error, check your carrier's support page or app for the correct one. The same digits can mean different things on different networks.
- *777# - Check prepaid account balance on some carriers
- *225# - Check postpaid bill balance on some carriers
- *646# - Check remaining plan minutes on some carriers
- *3282# - Request a usage summary on some carriers
iPhone Diagnostic Codes
iPhone has very few device level codes because iOS keeps most diagnostics internal. The two below are the ones worth knowing, and both are read only so they cannot change anything.
The Field Test code opens Apple's signal diagnostics screen, which shows technical cellular details. Apple has made specific signal readings harder to find in recent iOS versions, and the code must be typed in the dialer rather than saved as a contact.
- *#06# - Show the IMEI of your iPhone
- *3001#12345#* - Open Field Test mode for cellular signal details
Samsung Hardware Test Codes
Samsung's most useful code is the hardware test menu, which lets you check the screen, touch response, sensors, speakers, microphone, and cameras from one place. These codes are designed for Samsung Galaxy phones and should not be used on other brands.
Code availability changes with the One UI version and model, so some entries may not respond on the newest software. The codes below are the ones most commonly reported as working.
- *#0*# - Open the full hardware test menu
- *#06# - Show IMEI, MEID, and serial number
- *#1234# - Show software version details for AP, CP, and CSC
- *#0228# - Open battery status including voltage and temperature
- *#2663# - Show touchscreen firmware version
- *#34971539# - Show camera firmware details
- *#0808# - Open the USB settings menu
- *#9090# - Open diagnostic configuration
General Android Codes
Android codes that use the #*#code#*# pattern are processed by the phone and depend heavily on the manufacturer and Android version. Many of these were created for older devices, so expect some to do nothing on a current phone.
The most broadly useful one opens a phone information screen, though several makers including Samsung now restrict it. WiFi MAC address codes still respond on many devices, but remember that modern Android assigns a randomized MAC address per network by default, so the value you see may not be a fixed hardware address.
- *#06# - Show the IMEI number
- *#*#4636#*#* - Open phone and usage information where supported
- *#*#232338#*#* - Show the WiFi MAC address
- *#*#232331#*#* - Open the Bluetooth test
- *#*#1472365#*#* - Run a GPS test
- *#*#0588#*#* - Test the proximity sensor
Reset Codes and Safety
Some older codes triggered a factory reset straight from the dialer, which wiped the phone with little or no warning. On modern phones these are widely blocked. On Samsung, reset codes such as *#*#7780#*#* and *2767*3855# no longer work on recent One UI versions, and the phone information code is also restricted on newer builds.
That change is a safety improvement, not a bug. If you actually want to reset a phone, use the proper menu so you get confirmation prompts and a chance to back up first.
On Android, go to Settings > System > Reset options > Erase all data, and on iPhone go to Settings > General > Transfer or Reset iPhone. Both paths let you confirm before anything is erased.
When a Code Returns an Error
A common roadblock is the message Connection Problem or Invalid MMI Code, which usually means the network rejected the request rather than that your phone is broken. Weak signal, a SIM issue, or a confused dialer are the usual causes.
Start by confirming you typed every star and hash correctly, then restart the phone to clear the telephony stack. If a carrier code still fails, some networks need a short pause, which you can force by adding a comma at the end of the code before pressing call.
If the error continues, clear the dialer cache from Settings > Apps > Phone > Storage > Clear cache, reseat the SIM, and test in a strong signal area. A code that works for one person can still be unsupported on your specific carrier or model.
Frequently Asked Questions
Are USSD and MMI codes safe to use
Information and carrier codes are safe because they only display data or change a call setting. The risk comes from reset codes, so always confirm what a code does before running it and keep a recent backup.
Why does the same code do different things on two phones
MMI codes are processed by the phone, so the result depends on the manufacturer and software version. Carrier USSD codes depend on your network, which is why a balance code from one provider may fail or mean something else on another.
Does *#06# work on every phone
Yes, *#06# is one of the most universal codes and shows the IMEI on both iPhone and Android across virtually all carriers. It is read only and safe to use any time you need your IMEI.
Why did a reset code stop working
Phone makers disabled dialer based factory reset codes to prevent accidental data loss. To reset safely, use the reset menu in Settings so you get confirmation prompts and can back up first.
Why does my WiFi MAC code show a different address each time
Modern Android randomizes the WiFi MAC address per network for privacy, so the value a code reports may not be a single fixed hardware address. This is expected behavior and not a sign of a problem.
First published October 14, 2025. Last updated June 4, 2026.
