A well-known practice for backing up is a "3-2-1" strategy for files that cannot easily be recreated. The 3-2-1 guidelines are:
- 3 different copies - including the files on your computer.
- 2 different formats - typically, an external hard drive and online (in the cloud).
- 1 off-site - so if your house burns down, your data is accessible from somewhere else
A common practice is to back up to both an external hard drive and to a cloud backup service, while keeping the most current versions of files on your computer. If you are already backing up to an external hard drive, you may want to consider additionally backing up your files online, or perhaps on blu-ray discs that are stored in a separate location from the hard drive.
If you don't already own an external hard drive, you may want to purchase one. Typically, any drive which is at least 2 - 4 times the size of your computer's hard drive will work; thus, if you have a 500 GB hard drive inside your computer, you may want to purchase a 1 TB external hard drive or even a 2 TB external hard drive. These can easily be purchased on Amazon or at other locations for less than $100 and typically work well for 3 - 5 years, or longer.
Many computers come with built-in backup software, including Time Machine for macOS and Windows Backup for Microsoft Windows. There are a variety of online tutorials that show you how to use the backup software. This software can be used to backup to an external hard drive.
To backup to the cloud or to external discs (e.g. blu-ray), you will probably want to use a third-party service.
Stanford University also has a discount for an online backup subscription for its community; see the Eligibility section for how to purchase the discounted subscription for your personal use. If you are working for a department on campus and wish to back up your files related to your employment, check with your department for a possible backup option for employees. Due to its enterprise origins, however, this software may offer more functionality than desired for personal use.