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How to use secret codes on iPhone

iphone 13 pro display on in hand with metal background
(Image credit: Tom's Guide)

Most people probably don't know how to use secret codes on iPhone. In fact, most people probably don't even know that the iPhone has secret codes. But it does — and we've tried them.

Although most of the iPhone's features are tucked away within apps, widgets and the Control Center, there's a whole heap of hidden treasure waiting to be uncovered via the dialer. 

For more than 20 years, mobile devices have made use of Unstructured Supplementary Service Data (USSD) codes. They look like a series of numbers interspersed with hashtags and asterisks that you enter like a telephone number. 

Created for GSM phones, they connect directly to your service provider's computers and allow you access to hidden features. Many are specific to a particular carrier, but a good number of them will work regardless of which company you're signed up with. And they'll work whether you're using an older handset such as the iPhone SE or the latest iPhone 13 or iPhone 13 Pro

With that in mind, we will explore some of the most useful and interesting secret dialer codes. To use them, open the Phone app on your iPhone and tap Keyboard. You can then use the numbers and symbols on display.

How to find IMEI on iPhone

All cellphones have an International Mobile Equipment Identity (IMEI) number which is unique to each device. You may be asked to provide it if you want to unlock your iPhone for use with another network. The number can also come in handy if your iPhone is lost or stolen, allowing the handset to be identified.

1. To find your iPhone IMEI number, enter *#06#

A screenshot from an iPhone showing the phone app with a code to find an IMEI

(Image credit: Apple)

2. You do not have to press the green dial button. The information you need will automatically display.

A screenshot from an iPhone showing the phone app with the phone's IMEI

(Image credit: Apple)

How to hide your Caller ID on iPhone

When making a call on your iPhone, your phone number will be displayed on the device of the person you are calling. This is not always ideal, but you can quickly hide your Caller ID using a USSD code before the person's telephone number.

1. First, enter *67 (or, if you're outside the U.S., try #31#)

A screenshot from an iPhone showing the phone app with a withhold number code

(Image credit: Apple)

2. Now enter the person's number including the area code.

A screenshot from an iPhone showing the phone app with a withhold number code

(Image credit: Apple)

3. When you're ready to dial, tap the green button.

How to launch Field Test mode on iPhone

If you want to access technical information about your iPhone's cellular signal and connection, then you can make use of the hidden Field Test mode. 

Primarily designed for technicians and engineers, it allows you to check your network. Unfortunately, however, one of its main uses appears to have been axed in iOS 15 — the ability to view the strength of your signal as a numerical value.

Despite that, it's worth taking a look, if only out of curiosity, since it gives details of local network and cell towers. If nothing else, you may be surprised this feature exists at all, although Apple has been busy behind the scenes overhauling its appearance in recent years.

1. First, swipe down from the right-hand side of the iPhone screen to view the Control Center and turn off the Wi-Fi.

A screenshot from an iPhone showing the Control Center

(Image credit: Apple)

2. Now launch the Phone app and dial 3001#12345#

A screenshot from an iPhone showing the phone app with the code for Field Test

(Image credit: Apple)

3. You will be instantly taken to the Field Test screen which is split across two tabs: Dashboard and All Metrics. In truth, most of the information contained across these screens is unlikely to be of interest.

A screenshot from an iPhone showing the phone app with the options from the Field Test menu

(Image credit: Apple)

4. If you are on iOS 13 or iOS 14, however, you should tap All Metrics and, after scrolling down, tap Serving Cell Meas — which is under the LTE heading.

A screenshot from an iPhone showing the phone app with the options from the Field Test menu

(Image credit: Apple)

5. Look for rsrp0 and rspr1 (indicating the towers closest to you). These show the cellular signal strength in decibel-milliwatts. To indicate a strong signal, the number need to be around the -40 mark. When the number reaches -100, you're in an area with a much poorer signal.

How to divert incoming calls on iPhone

When your iPhone is busy because you are on a call, you can have other incoming calls diverted to another number. This could be to a landline or another cellphone number. It is also possible to divert calls if your iPhone is unreachable or have them diverted if you don't answer or reply.

1. Start by identifying what you want to do.

To forward calls when you don't answer, dial *61*

To forward calls when your iPhone is unreachable, dial *62*

To forward calls when your iPhone is busy, dial *67*

A screenshot from an iPhone showing the phone app with codes for call diverting

(Image credit: Apple)

2. Enter the number you want to divert to, then tap #

A screenshot from an iPhone showing the phone app with a code to divert calls

(Image credit: Apple)

3. Now tap the green Dial button. You should get a confirmation. If this does not work, check your network for the alternative codes.

4. To deactivate these services, enter #61#, #62# or #67# depending on the original code and tap the green Dial button again.

A screenshot from an iPhone showing the phone app with the code to divert calls

(Image credit: Apple)

5. If you want to discover the current status of any of these services, dial *#61#, *#62# or *#67#

A screenshot from an iPhone showing the phone app with the options for call waiting

(Image credit: Apple)

How to enable call waiting on iPhone

If someone is trying to get through while you're on a call and you would like to be informed, ensure call waiting is enabled. This will also give you an option to answer the new call.

1. Simply dial *43# and tap the green button.

A screenshot from an iPhone showing the phone app with the codes for call waiting

(Image credit: Apple)

2. Now tap Dismiss when the confirmation screen appears.

A screenshot from an iPhone showing the phone app with the call waiting options

(Image credit: Apple)

3. To stop call waiting, dial #43#.

How to prevent outgoing calls on iPhone

If you are passing your iPhone to someone, you may want to prevent them from using the device to make a call. 

1. To begin, dial *33*

A screenshot from an iPhone showing the phone app with the codes for call barring

(Image credit: Apple)

2. Now enter a PIN followed by # – this will prevent someone else easily turning the function off.

A screenshot from an iPhone showing the phone app with the codes for call barring

(Image credit: Apple)

3. Tap the green Dial button and tap Dismiss when you receive the confirmation.

4. To disable code barring, dial #33*your pin#.

How to keep experimenting with secret codes

Some secret codes will work on your iPhone with your carrier, but some will not. The only way to truly find out is to give them a go. Here, we list some other USSD codes that you could try. With a bit of luck, you'll unearth some usable treasures.

Check the number of minutes left on a contract: *646#

Discover your current balance: *225#

See how many calls you have missed: *#61#

Check the SMS Center: #5005*7672#

Enable Enhanced Full Rate mode to improve voice quality: *3370#

More iPhone and iOS tips

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David Crookes

David Crookes is a freelance writer, reporter, editor and author. He has written for technology and gaming magazines including Retro Gamer, Web User, Micro Mart, MagPi, Android, iCreate, Total PC Gaming, T3 and Macworld. He has also covered crime, history, politics, education, health, sport, film, music and more, and been a producer for BBC Radio 5 Live.