A digital footprint is a trail of data you create while using the Internet. It includes the websites you visit, emails you send, and information you submit to online services.
A "passive digital footprint" is a data trail you unintentionally leave online. For example, when you visit a website, the web server may log your IP address, which identifies your Internet service provider and your approximate location. While your IP address may change and does not include any personal information, it is still considered part of your digital footprint. A more personal aspect of your passive digital footprint is your search history, which is saved by some search engines while you are logged in.
An "active digital footprint" includes data that you intentionally submit online. Sending an email contributes to your active digital footprint, since you expect the data be seen and/or saved by another person. The more email you send, the more your digital footprint grows. Since most people save their email online, the messages you send can easily remain online for several years or more.
Publishing a blog and posting social media updates are another popular ways to expand your digital footprint. Every tweet you post on Twitter, every status update you publish on Facebook, and every photo you share on Instagram contributes to your digital footprint. The more you spend time on social networking websites, the larger your digital footprint will be. Even "liking" a page or a Facebook post adds to your digital footprint, since the data is saved on Facebook's servers.
Everyone who uses the Internet has a digital footprint, so it is not something to be worried about. However, it is wise to consider what trail of data you are leaving behind. For example, understanding your digital footprint may prevent you from sending a scathing email, since the message might remain online forever. It may also lead you to be more discerning in what you publish on social media websites. While you can often delete content from social media sites, once digital data has been shared online, there is no guarantee you will ever be able to remove it from the Internet.