Hidden Secret Codes for all Android Devices [LATEST]

One of the most popular practices amongst software developers is to leave ‘backdoors’ within the code, which essentially allow anyone with knowledge to get into the system at a much deeper level than you’d expect from an end-user. These backdoors aren’t always with a malicious intent; most of the time, they allow the OEM or programmer to get into the system for troubleshooting when other, usual modes of access have been blocked. They can be quite friendly and helpful if you know what you’re doing.
Smartphones have a good share of these as well, where they’re generally known as secret codes. Most of the time, these numeric/symbolic sequences allow you to access hidden menus, diagnostic tests, areas that could change some of the most basic parameters of your device and whatnot. These secret codes, in fact, have not been exclusive to smartphones, but have long been a part of the dumb-phones and then the feature-phones before most major OEMs joined the smartphone bandwagon. For those devices that run Android, certain codes are shared across the board, and hence, can be used on a variety of devices.
Android codes
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What follows is a collection of some of the secret codes common to the Android platform. All of these would be entered through the phone dialer (just punch in the sequence as shown). Since most hidden menus are manufacturer specific, there’s no guarantee that they’ll work across all Android smartphones, but you can try them out nevertheless on your Samsung, HTC, Motorola, Sony and other devices. Be advised, though, that some of these can cause serious changes to your device’s configuration, so don’t play with something that you don’t fully understand.
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Update x1: More codes!
Codes specific to HTC devices only:
Note: Not all codes are supported in a phone. Try these codes at your own risk.
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