What are the differences between stock ROMs and custom ROMs?


All right, so you’ve got an Android device, you kind of want to try something new, you want to switch to a custom ROM because you’re frustrated with the way your device is functioning, or it’s running an outdated version of Android, or you’re just bored. Then again, you’re not exactly sure about the improvements/decrements you’ll have on board, or you’re not aware what the primary differences between your stock ROM and a custom ROM. Other articles on Google didn’t help as well, because, well, those are probably as outdated as your stock ROM (shots fired). No worries, let us explain.

For some reference, you might want to read the following FAQ articles beforehand, so that you don’t get stuck somewhere in the middle of this post:
> Stock ROMs Explained: Merits & Demerits
> Custom ROMs Explained: Merits & Demerits
> AOSP vs Stock Android vs Stock ROM

Okay, one last little disclaimer (kind of) paragraph before we get to the explaining, we just wanted to let you know that this article just puts in front of you the basic differences between a ‘general’ stock ROM and a ‘general’ custom ROM. Some aspects of this comparison might be limited to a specific ROM, and some might be true for all. The point of this article is just to set the differences apart, and not to lure you into flashing a custom ROM or going back to the stock ROM. Everyone has different needs, so we have a separate article that’ll try to help you know whether or not you actually need a custom ROM at all, which you can check here.

So, here’s all the stuff that sets Stock ROMs and Custom ROMs apart.

1. Privacy & Security

Because the big G is literally putting user security and privacy over everything else these days, we decided to put this part on the top of our list as well. The general belief is that stock ROMs are more secure than custom ones, and although our view might start some burning conversations, we’d say that’s not entirely true. There have been multiple cases of manufacturers gaining access to (and transferring) sensitive user data via their stock ROMs. Though this can be disregarded by saying that they do this for R&D, it still is a breach of user privacy.
About the system security part, there are absolutely no chances of Android getting infected with the viruses because Linux is virus-proof. Added security props like SafetyNet is easily available across all kind of ROMs if you use the proprietary set of Google apps (GApps), and Android now natively supports encryption of user data (yeah, custom ROMs included), so you can make sure no third party gets access to it. So, the only way your device gets ‘infected’ is with malware, bloatware (that some stock ROMs have in abundance), and adware (again, some OEMs love to stuff these into their stock ROMs). Except for some closed-source forks, custom ROMs mostly do not come loaded with either bloat, or malware, or adware.
Heck, they even let you decide whether or not you want to keep GApps, that are mandatory on all stock ROMs. The benefit? You can skip GApps and use other open-source app alternatives to be safe from big G tracking you from the device level. Want to run Android without Google Apps? Here’s how you can. Anyways, the point is, custom ROMs are generally just as secure, and even better in terms of privacy than stock ROMs. Oh, and did we mention that we also have a post explaining the security aspect of custom ROMs?

2. User Interface

Your stock ROM might have big cartoony icons, with all apps on the homescreen and no app-drawer. Or it might have some fancy font and 3d animations across the system. User Interface across stock ROMs vary massively and are defined by manufacturers. Also, when you compare your stock ROM to a custom ROM, you shall find differences in the UI. Straight from the boot animation, to the homescreen, the status bar, the phone settings app, the menus, things are often different when you look at them.

3. Customization

Another key difference between a stock ROM and a custom ROM will be the sheer freedom of customizing Android to suit one’s needs. We’re not just talking about visual customization here, things are different from the roots, the features and small tweaks that make big differences in user experience. Some stock ROMs are filled to the brim with features, themes, wallpapers, nifty tricks and more, that aren’t available natively on some custom ROMs. Some stock ROMs come without any extra fancy tweaks or features and just run the absolutely necessary apps and services.
The bottom line is, on your stock ROM, you’re limited to the amount of customization that you can do (or you can’t). Custom ROMs often give the user the freedom to customize almost every aspect of the OS. Don’t need a feature? Okay, you won’t have that feature putting an extra load on the system. Bored with the default visual look of the phone? Super-theme the OS with apps like Substratum! Need a specific feature? Cool, you’ll have it with some module or port. So, yeah, the ability and the amount of customization you can do are different on stock ROMs and custom ones.

4. Updates

Admittedly, manufacturers have gotten really good with pushing system updates to their stock ROMs these days. A healthy system update schedule makes sure that your device gets access to the latest features, as well as, rid of bugs and issues. This varies across brands and ROMs. Some manufacturers push a couple of major Android version updates, while some don’t provide even one. Some push security patches every 3 months, while some do it every month. Some brands are swift with fixing bugs, while others take forever.
With custom ROMs though, you’re almost certainly getting a newer version of Android, as well as security patches for your device, in case the manufacturer has decided to abandon software development on it. We should have included this ‘security patch’ part in the first topic (Privacy & Security) itself, but then this is a part of system updates, so we decided to keep it here. Bug fixes and feature requests are also often served faster on custom ROMs, generally, because there is a relatively smaller user base and relatively less thorough testing.

5. Pre-installed Apps & Features

One of the basic differences between a stock ROM and a custom one is the number of apps and features baked into them. Some stock ROMs, like MIUI, have apps and features literally filled to the throat, most of which people will never use. There are your regular Google apps, and then there are MIUI apps (those are literally just alternatives of GApps, and do basically the same stuff). They’re just there for the sake of being there. On the other hand, the stock ROMs on something like the Pixel devices have just the necessary features but have many Google apps preloaded.
Same case with custom ROMs. Some have a lot of apps and features pre-installed, while others run light with just the absolutely necessary ones. Based on whichever type of user you are, you might find a custom ROM either lighter or heavier than the stock one. Some custom ROMs even have features from multiple ROMs baked into them!

6. Performance

Probably the biggest reason why people switch to custom ROMs is the difference (read: improvements) in performance, in regards to the CPU, GPU, RAM, battery, cameras, and even other stuff like audio and display. Depending on the number of features and apps (bloat) loaded into the ROM of your choice, you might notice a difference in the performance. In some custom ROMs, performance might take a hit, owing to much more features, making the ROM heavy; while on some the difference in performance can be night and day.

7. Stability

Stock ROMs go through very thorough testing by the developers and private software testers, whereas the custom ones depend mostly on community testing. That means, on most of the custom ROMs, the ROM has lesser bugs if there are more users. Basically, bugs in custom ROMs are inversely proportional to the number of users. The stability on most custom ROMs is less than the stock counterparts. That said though, this varies from device-to-device, and ROM-to-ROM. On some devices, even the stock ones are buggy and unstable, and in some cases, custom ones are stable (af).

So, that’s all for this comparison. While these were the major differences, there still are much more differences that matter when you want to decide whether or not to switch to a custom ROM. We have device-specific posts, so make sure to check them out to know what exactly is different on custom ROMs for your device.

Happy flashing!