There isn't anything wrong with most out-of-the-box experiences, but more-daring and tech-savvy users who tire of being at the mercy and discretion of carriers and handset makers might be interested in pushing their Android devices to new limits and root them.
Around since the early days of the T-Mobile G1 (HTC Dream), rooting can add functionality to a phone and often extend the life of the device. The T-Mobile G1, for instance, was officially supported through Android 1.6 Donut, but if you rooted the phone, you could load an alternative developer-made version of the OS that offered most of Android 2.2 Froyo's features.
I'm going to share some of rooting's benefits and risks, where to find some great replacements for the default Android OS, and a few other tips. If you have any of your own that I haven't covered here, please add them to the comments below.
Editors' note: This post was updated on July 2, 2013, with more-current information.
What is rooting?Rooting, in a nutshell, is the process that provides users with full administrator control and access to an Android smartphone or tablet. Similar to "jailbreaking" an iOS device, this is often done in order to bypass carrier or handset-maker limitations or restrictions. Once you achieve "root access," you can replace or alter applications and system settings, run specialized apps, and more.
One of the more common reasons to root a phone is to replace the operating system with a ROM, another developer's version of the OS that also gives you more control over details. In rooting culture, we'd call that "flashing a custom ROM."
The process of rooting an Android phone varies for each device, but seems to have been streamlined over time. Google's Nexus line of phones, such as the LG-made Nexus 4, appeals to developers and techie types and are among the most often rooted models. With that in mind, you'll also find that popular devices like the Samsung Galaxy S4 and HTC One have plenty of custom ROMs to choose from.
Note that rooting will void the device warranty; however, flashing a stock ROM can revert things back to their original state.
Why root?There are multiple reasons for you to consider rooting your Android handset, some more obvious than others. Chief among the benefits is the ability to remove any unwanted apps and games that your carrier or phone maker installs before you ever unwrap your phone. Rather than simply disabling these bloatware titles, which is often the most you can do within Android, rooting can grant you a full uninstallation. Deleting apps you'll never use can also free up some additional storage capacity.
Another main benefit of rooting is to enable faster platform updates. The time it takes for Google to announce a new version of Android to the time your carrier pushes it to your device can be weeks, months, or even longer. Once rooted, you can often get some of the new platform features through custom ROMs in short order. This could, for some users, add years of life to an Android handset -- rather than buy a new phone, flash a new ROM.
Other reasons to root a phone include being able to perform complete device backups, integrate tethering and mobile hot-spot features, and extend the device's battery life through new-found settings and controls.
What are the risks?As I mentioned above, rooting your device can void your warranty. This is perhaps the biggest risk associated with playing around with your phone. If you run into big trouble and you've added a custom ROM build, your manufacturer and carrier likely won't help you out.
In most cases, you'll be able to overturn any ROM you flash, returning to the phone's stock Android OS with as much ease as you installed the new ROM in the first place. However, a word of caution: If you're not careful, or don't follow the steps properly, you could end up with a glorified paperweight. Yes, I'm talking about "bricking" your device. It's vitally important that you exercise caution when attempting to root your phone and pay close attention to what you're doing.
Stick to the more reputable sources for help and feedback, and look for the most recent news about ROMs and your particular Android device. Along those lines, you'll also want to ensure that you read through everything you can before starting down this road. If you're in a forum thread, skim the replies to see if there are issues or problems with your particular handset.
Helping handsFor help with rooting, I would first recommend XDA developers, AndroidCentral forums, Androidforums, and Rootzwiki. I also suggest checking Google+ as a good source for rooting and modding news and feedback. The rooting scene is not some secret underground Fight Club; you'll find plenty of documented help for rooting your phone. Filter your results by date, read through the details, and understand what it is you are about to do.
More about ROMsFor all practical purposes, (custom) ROMs are replacement firmware for Android devices that provide features or options not found in the stock OS experience. Often built from the official files of Android or kernel source code, there are more than a few notable ROMs to consider. Among the more popular custom ROMs are CyanogenMod, Paranoid Android, MIUI, and AOKP (Android Open Kang Project). There are, of course, countless others to check out, with more arriving almost daily.
In terms of sheer support and development, CyanogenMod is the clear leader in this field. The number of supported devices is unparalleled, and the community has long rallied around this ROM. This is not meant to say that it's necessarily the "best" ROM; beauty is in the eye of the beholder.
Closely resembling the stock Android experience, CyanogenMod has been known to introduce features that later end up in official builds of Android. As of today there are more than 4.2 million active installations of CyanogenMod releases, with v10.1 (based on Android 4.2 Jelly Bean) being the latest.
One newly introduced feature worth noting is a "Run in Incognito Mode," which lets you privately use an app and manage its permissions. Rather than installing an app and agreeing to all permissions, this mode allows you to restrict data to certain apps. In theory, you could disallow a particular app from using GPS, accessing contacts, and more.
Among other features, Paranoid Android's HALO ROM provides users with a blend of Facebook's Chat Heads with Samsung's multiwindow functionality. The floating, circular notifications can be docked anywhere on the left or right side of the display and work with a variety of apps. This handy feature keeps you notified of Gmail, Hangouts, Google Now, and other system-wide alerts.
Where to look for ROMsForums are going to be a great place to keep yourself plugged in, but the larger ROM developers will provide their own Web sites. Aside from the aforementioned custom ROMs, others that have gained a strong following include SynergyROM, Slim Bean, LiquidSmooth, RevoltROM, and Xylon. Be warned: talking about ROMs can often result in heated debate as to which is better or offers more options.
Noteworthy appsAside from installing custom ROMs, rooting your phone opens the door to installing new apps and gaining extended device management and security functionality beyond what comes with the usual Android OS experience.
Should you decide to not load a new ROM interface, you can still install apps that add new levels of functionality to your rooted Android phone. Today's more popular titles include ROM Toolbox Pro, Titanium Backup, Touch Control, Cerberus anti-theft, and SetCPU. The appeal of each will vary depending upon on how much you want to tweak your Android experience.
For those of you who plan to flash ROMs on a regular basis, I recommend starting with ROM Manager. This utility lets you manage backups and recoveries, install ROMs, and other handy functions. While it is available as a free app, the premium client has ROM update notifications, nightly ROM downloads, set automatic backups, and other features.
Backup plansWhen it comes to rooting your phone, it is always a good idea to have backup plans in place. After all, you'll need something to fall back on should you run into an issue with an untested or experimental ROM. While Titanium Backup seems to be the most popular, Carbon has gained quite a fan base. Regardless of which route you take, it's important to create a backup and test it before you apply a custom ROM.
Become familiar with the process and make sure that you'll be able to restore things in the event of a catastrophe. It might take some practice and you could spend more time than you'd like creating this backup, but it could be all that stands between you and expensive phone repair.
Indeed, there is plenty to consider when it comes to rooting your Android phone. Rest assured, though, that no matter how daunting the task might seem, there's a large community of users out there who will have your back. And while the actual rooting process varies with each handset model, on the whole, it isn't as difficult as it may sound.
If you've read through this post and still don't know if rooting is for you, my suggestion is to take the time to mull it over. Replacing the default Android OS certainly isn't for everyone and there's quite a bit more on the topic besides. For many people, myself included, the reward of tweaking your Android phone to have it exactly the way you want it is worth the risk.
Do you have any adventures in rooting and ROMs? Share them in the comments.