Everybody uses a smartphone these days but not very many people know that their phone has a number of hidden. Codes that can make their life easier. The USSD protocol allows you to access hidden features you didn’t know about right from your smartphone’s dialer.
Unstructured Supplementary Service Data (USSD)—sometimes known as “quick codes” or “feature codes”—is an extra-UI protocol, which allows people to access hidden features. This protocol was originally created for GSM phones, but can be found on CDMA devices as well.
These backchannels are publicly available and it allow users to directly communicate with their service provider’s computers and/or access back-end features in their device. They are accessed by inputting them into the phone’s dialer (the screen you use to start a phone call) and usually begin and end with the * or # keys with a sequence of numbers in between.
If you really want to try them out, your best bet may be to Google your phone’s make and carrier + “USSD” for a tailored, comprehensive list. Here are five codes that cut across most phones.
Check Your Call Forwarding: *#67#
This code allows you to check which number your phone is currently forwarding calls to when you’re busy or reject a call.
By default, this is probably your carrier’s voicemail service, but you can change it to forward to a different number (a home number, office number, or third-party answering service for example). On an iPhone, you can change this number by going to Settings > Phone > Call Forwarding. On Android (varies from system to system), tap the Phone app > hamburger icon > Settings > Call > More Settings > Call forwarding
Hide Your Phone From Caller ID: #31#
This code apparently only works on Android. But entering this code prompted a pop-up stating that my Caller ID had been disabled. In order to re-instate Caller ID, enter *31# .
Field Mode: *3001#12345#*
Type *3001#12345#* into your phone’s dialer and then press the green call button to access “Field Mode,” which can give you access to info about local networks and cell towers.
You’ll probably never ever have to know about your local cell tower’s “Measured RSSi,” but it’s fun to look around for a bit.
General Test Mode: *#0*#
This probably only works on Android phones but this prompts a library of different phone operations, which could be operated with a single push (e.g. Sleep, Front Cam, Vibration).
Display your IMEI: *#06#
To access it, type in the above code, and then the green call button to prompt your IMEI number (or your International Mobile Station Equipment Identity number). The IMEI is unique to your device. Among other things, the number can help “blacklist” stolen devices or help with customer support.