How to Open Engineering Mode in OPPO F21s Pro 4G

The developers of most Android-based operating systems do not provide users with all the customisation options for their smartphones. Highly specialised and dangerous features are hidden in the engineering mode or developer mode. This is for the safety of the user, as many settings in the engineering mode can drastically change the way the device works.

For example, the most popular function in the Engineering mode is Volume Boost. This function allows you to increase the volume beyond the maximum level intended by the smartphone's designers. The guaranteed result is that the speakers will fail sooner.

However, the tech menu is still necessary for some users and all phone manufacturers offer free access to it, with the possible exception of Apple's shopping mode. However, you need to know special USSD codes that can be used to open engineering mode in the OPPO F21s Pro 4G.

OPPO F21s Pro 4G special codes and where they can be obtained

The codes that unlock certain functions are known only to the smartphone manufacturer. They are usually found in the technical documentation, a small booklet that comes in the phone's box and that 95% of people throw away after opening.

Another way to find out the USSD code for a particular model is to contact the manufacturer directly. A good example of this is Chinese brands, which discreetly answer this question on popular marketplaces.

The last sure-fire way is to simply search the internet. Every code for a particular device has been known for a long time, some of them even before the device was released. All you have to do now is type "code for OPPO F21s Pro 4G Menu Engineering" in any search engine.

Quick guide

USSD codes are a series of numbers and symbols that you need to enter into your phone or call application. They are essentially entered in the same place you make a call on your smartphone.

1. To do this, you need to open the dialling window. It will either open automatically when you log in to the application, or you can click on a small icon at the bottom of the screen.

2. Enter the code you found earlier into the selection window. There is no need to press any buttons after entering the code, the engineering menu will open immediately.
3. Look forward to an open engineering mode. Read the following information to avoid making any stupid mistakes.

Use all functions of the engineering menu at your own risk. We strongly advise you not to enable or disable anything you do not understand. Another popular feature is factory unlock. It is usually used to gain root privileges. However, enabling factory lock is written into the hardware of the device.

This is not about stealing data, it is about voiding the manufacturer's warranty because you have activated a feature that was not originally available to you. And if you catch a virus instead of getting root privileges, which is very common, the manufacturer has the right to deny you warranty support.

So once again: Never turn on or off features you do not understand!

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