So you think you’re a smartphone expert. You know your iPhone or Android phone inside and out and you constantly help your friends and family with their mobile problems. Well, we hate to break it to you, but there are still plenty of things that even the savviest smartphone users out there don’t know about.

For example, did you know that your iPhone or Android phone has tons of secret hidden menus that you can only access by dialing special codes into the phone app?

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Older cell phone users out there may remember the days of dumb phones, when a phone call to customer service would end with a rep instructing you to dial a bizarre code into your phone to update it or reset some settings.

Those days are long gone, thankfully, but those mysterious hidden codes live on.

Here are some codes you can dial into the phone app that will access hidden information and menus in the iPhone:

*#06# – Displays IMEI

*3001#12345#* + “Call” – Accesses a hidden Field Test menu

*#43# + “Call” – Displays call waiting status

*43# + “Call” – Enables call waiting

#43# + “Call” – Disables call waiting

*#21# – Displays call forwarding status

##002# + “Call” – Disables all call forwarding

*33*pin# – Enables call barring

#33*pin# – Disables call barring

#31#phone-number + “Call” – Blocks caller ID for the current phone call

*3370# + “Call” – Enables “Enhanced Full Rate” and improves voice quality on GSM networks (may impact battery life)

*#5005*7672# + “Call” – Displays your carrier’s message center phone number

Don’t worry, Android users, there’s some great hidden stuff on your phones as well. The problem, of course, is that Android phones all differ so much based on model and manufacturer.

Here are two notable ones — the first will work on most Android phones and the second will work on all Android phones:

*#*#4636#*#* – Accesses a hidden test menu with sections for network, battery information and usage stats.

Under the “About phone” option in Settings, tap “Build number” seven times – this will enable a new “Developer options” menu in Settings that gives you access to a treasure trove of functions.

For more hidden Android codes that will work on various phones, check out this old Reddit thread.