You can lump the scenarios where using a VPN is important into two general buckets: when accessing sensitive information or using insecure networks.

Public Wi-Fi networks are the most common example of where VPNs provide extra security. Because anyone can join the network and you don’t know how it’s been configured, someone could theoretically snoop on what you’re doing using open Wi-Fi. There’s also a risk of attacker setting up a fake network with the same name as a trusted one at a coffee shop or airport. 

Running a VPN while you’re using public networks creates an encrypted tunnel between you and what you’re accessing, helping shield your data from cybercriminals who may be lurking in these public spaces. The same logic applies for any websites that still don’t use a secure HTTPS connection. When connected via HTTPS, someone spying on the network can see that you’re accessing the site, but can’t view anything you’re entering there. The vast majority of major sites default to HTTPS, but a VPN can provide a fallback for the fraction that don’t. 

VPNs help hide your internet activity from your internet service provider. According to a study by the FTC, ISPs frequently collect information about your devices, internet history, network performance and usage habits, often selling said information to third parties. Using a VPN prevents your ISP from seeing what websites you visit and what you’re doing, though it still knows you’re using a VPN and how much data you’re moving. However, VPNs don’t hide your entire search history; your browser still keeps a log of where you visit, and if logged into your Google account, that profile keeps a log of your activity across its platforms.

These privacy concerns are doubly important when traveling, particularly if you’re somewhere where internet access is monitored or restricted. In these cases, VPNs are a good way to keep responsible internet usage private. Also, it may help you access American streaming services abroad — streaming-compatible VPNs are a key travel hack if you’re halfway through The Sopranos when departing for an international trip. Moreover, using your VPN to change your location can unlock the country-specific catalogs of services like Netflix.

You may also want to use a VPN as a backup layer when accessing sensitive information, such as your email, bank account or healthcare plan. While a VPN doesn’t guarantee that your information stays protected, it can help prevent man-in-the-middle attacks, where crooks steal your information in transit. It won’t save you from tricksters duping you into divulging your bank details, but it could prevent them from spying on your Amazon transactions. As such, I always check that my VPN is functioning before accessing sensitive information on my phone or laptop.