One of my favorite Chromebook features is how fast and easy it is to perform a factory reset. That might seem odd, but it's a simple way to keep it running smoothly. Google calls the feature Powerwash and it can be done in under a minute. It's also one of the features that make Chromebooks so good for sharing. Just Powerwash your Chromebook and someone else can use it and you won't need to worry about them accessing your info.
Also, although Chromebooks are inherently secure, that doesn't mean you can't install a malfunctioning extension or a web app that misbehaves. Uninstalling the offending extension or app can typically fix the problem, but if that doesn't work, a reset should do the trick. The same goes for other wonky behavior you may experience.
A Powerwash is a breeze to do, too. I've detailed the steps below. Also, while I included how to locate most settings by navigating menus, it is generally easier to use the built-in Launcher search feature to find exactly what you're looking for fast. The Launcher can be opened by clicking the radial button at the far left on the shelf at the bottom of your screen; a two-finger swipe up from the shelf; or hitting the Search key.
Back up your files first
Since you'll be wiping your Chromebook's internal storage, you'll want to back up any files you want to keep to the cloud or an external drive. This isn't as painful as you might think because a lot of what you do on a Chromebook is already synced to your Google account -- from apps and extensions to passwords and Wi-Fi networks. (To see what's set up to sync, go to the Accounts section of the Settings menu. Click on Sync and Google services and select Manage what you sync.)
What doesn't automatically get synced are files saved locally to the Downloads folder. Linux and Play files are also stored locally. To see and back up those and any other files, open the Files app (or search for Files with the Launcher). The left-side navigation panel in Files shows you all your folders.
You'll also see your Google Drive folder (that's what I use for backups) as well as external storage. If your Chromebook has a microSD card slot, for example, you can save files to a card or attach an external drive. You can copy and paste files to Google Drive or external storage or just drag and drop them. The Powerwash only deletes what's on your Chromebook's built-in storage.
Give it a good scrub
Once your files are all backed up, you can start the Powerwash. Go to the Settings menu by clicking on the time on the far right side of the shelf at the bottom of your screen. That will pop up the quick settings panel. Click on the cog icon at the top of the panel.
Under the Advanced section at the bottom of the menu (you may need to click on Advanced to expand the options) you'll find Reset settings and Powerwash. Click the Reset button and you're on your way. You can also search for Powerwash with the Launcher or Search key to access it. And, if you aren't or can't sign in and want to Powerwash a Chromebook, press and hold Ctrl plus Alt plus Shift plus r to begin the reset.
There are a couple of warnings you'll need to click through to confirm that you know what you're about to do. After that, the Powerwash begins. And it is fast, too, generally taking less than a minute to complete. Also, if Chrome OS isn't up to date or there's a firmware update available for your Chromebook, it will ask if you want to install the updates.
Sign in and start working
When the Powerwash cycle completes, the Chromebook will restart and you'll be greeted with the Welcome screen. Just follow the prompts to sign in to your Google account and you're done. Anything you have set to sync will do so. That includes installing web and Android apps and browser extensions and any updates. Otherwise, the internal drive should be clean and your Chromebook running like new.