[Android] What are Custom and Stock ROM, Root, Flash, Firmware

Those who have a poor understanding of Android may not have heard of these terms from the title of the article, or they have but they don't know what they mean. And those who are a little more interested in this OS certainly know what they mean. So, who is this article for? For users who would like to discover the true power of Android but are not sure if it is for them.

First, let's clarify what's what!

ROM stands for Read-Only Memory. It is the part in the internal memory of the device where the Firmware is located and which cannot be changed by normal use of the device. This is done to protect the system from users, ie. to prevent damage to the system due to user negligence. In the Android world, when we say "ROM", we mean the Firmware itself (system) and not the memory in which that system is located - Read Only memory.

The firmware is an intact system that comes with the phone and is stored in read-only memory and is protected from modification for protection. However, the Read-Only memory can be modified by the user. It is only enough to use the appropriate software that allows it, ie. to root the device.

The root is, therefore, the process of unlocking the device (not the SIM card and the network!) And thus the user gets complete control over every part of the device, even the part where the system is. Now the user can install other systems, ie. delete the original and insert another one into that former Read Only memory.

Flashing is the process of inserting a new system in place of the old one, and the process requires a root approach.

So what is Stock ROM?

Stock is the original ROM (Firmware), comes with the phone, and is intended for every user because nothing can be changed that would cause problems on the device. Stock ROM can still be unlocked, ie. Root-ing, so the user can install applications that require Root, or install (Flashing) another system.

The worst-case scenario is Hard Brick and then the device becomes completely unusable, there is no way to fix it. But that shouldn't discourage you because the chances are miserable. Even if you insert the ROM of another device, Soft Brick will only happen, and that can be easily solved by reinstalling the appropriate system - I personally took a risk and tried it on several devices for educational purposes.

Ok, this is Stock ROM, and what is Custom ROM?

Well, you guessed it, it's a modified ROM. It is installed after the device is rooted (we said what Root allows). The Android community is huge, there are a lot of developers (users like you and me) who take the original Android Code (because Android is open source) and create a system to their liking, ie. cook! Yes, the ROM is "cooked" in the "kitchen" tool;) Or, there are Stock-based Custom ROMs and these are redesigned Stock ROMs.

Stock-based Custom ROM is basically a Stock ROM officially issued by the device manufacturer (eg Samsung, and again Samsung took pure Android and modified it for its devices) and someone improved it - released Bloatware (useless applications), set some parameters for faster device operation, inserted some of your scripts, applications, improved existing ones… Why would someone do that and not make a clean Custom ROM? Since some device manufacturers create applications that work only on their original system and some parts of the system are encrypted and cannot be copied and pasted into pure Custom ROM. Because of all this, a clean Custom ROM for such a device has a lot of drawbacks and the device itself is quite deprived and we cannot use its full potential. Therefore, users of such devices are hesitant whether to switch to pure Custom ROM, stay on Stock, or take Stock-based Custom ROM.

To summarize the previous part:

1. We have a Stock ROM that comes with the device and is designed for everyone
2. We can root Stock ROMs and provide ourselves with full access to the system, as well as enable the installation of Custom ROMs
3. Stock-based ROM is a modified original Stock ROM
4. Pure Custom ROM is based on pure Android Code

To return to the Root part…

I mentioned that Root is a bit dangerous for the device, but it's not that scary. It really brings us a lot of opportunities. One of them is the ability to install Custom ROMs and Kernels, adjust the processor, memory, screen, sound, keys… literally every part of the device. And there are tons of applications that require ROOT and are very useful. Only the Greenify app is the number one reason for many to ROOT their device. Xposed is probably in second or third place. And because of all that, your device can work much faster and better, all with less battery consumption! If you buy the Flagship (Flagship models are the most popular models on the market at the time they appear - eg Galaxy S6) model now, you are insured for the next 4-5 years. Because, when the manufacturer stops sending OTA (over-to-air, ie official) updates, the user community will continue to develop ROMs for that model, because it is popular and has good hardware. That's why I always recommend buying Flagship models precisely because they will last longer and will be in line with the performance of a few found models (with Custom ROMs).

And finally: why Stock ROM?

The stock has several advantages: it is stable, you have OTA updates (1-click install), you do not have to root the device (because, among other things, you lose the warranty), and you can use all manufacturer applications and all device options…

As for the flaws: OTA updates are mostly late to us (Serbia), the system has unnecessary applications and is bigger (up to 4x!), Official updates are sent around two versions of Android and after that, the phone no longer has official support for new versions, developer support is no…

And if you opt for Custom ROM…

Advantages: above all: great choice! Then, complete control over the device, overclock, undervolt, tons of useful applications that do not work on Stock ROMs, the system is much smaller and lighter, a bunch of scripts in the system for better device operation, hacking (games, other users…), battery longer lasts, the phone runs faster, more frequent updates, direct communication with the developer (s), older devices may become reusable…

Disadvantages: risk of error and loss of some data (personal files are 99% secure), lack of some functions (which exist only on the original system and cannot be copied due to protection), updating the system is done manually and is a little harder, some Manufacturer's applications require Stock ROM, loss of warranty (due to Root), possible errors in the system, so it is desirable to monitor the status of the ROM on the page where it is presented (

Who is Stock and Who is Custom ROM for?

Stock is for those who want to have a phone for the sake of the phone and are not interested in additional features. So, it is important that it works and works well, without the risk of system crashes and the like.

Custom ROMs are for those who want more from their phone with a dose of risk. If you are ready to take that risk and expand your knowledge of Android, and thus upgrade your device software, head to the XDA Developers forum and find your device on the list!

I hope this article has clarified some of your doubts. If you have questions, leave them below in the comments.

Source: personal experience