A VPN (virtual private network) can let you surf privately on an untrusted network, access blocked websites from work or school, view geo-restricted content, or cloak yourself from the prying eyes of advertisers. Here are six of our favorite VPN services.

Hotspot Shield VPN (Windows, Mac, Android, iOS)

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Nervous about your privacy while surfing the Net? Hotspot Shield VPN shields your online activity with banking-level encryption, no matter which network you're on. You can try it for free for seven days before upgrading to a paid monthly or annual subscription.

CyberGhost VPN (Windows, Mac, Android, iOS)

Surf unseen by advertisers with CyberGhost VPN. This app supports the most secure encryption technology, the L2TP/IPSec VPN protocol, so you can feel confident that your every move isn't being tracked. VPN service for desktops is free, but you need a premium subscription for mobile devices.

Vpn One Click (Windows, Mac, Android, iOS)

There's no reason to miss watching your favorite international TV shows just because you live in the US. With Vpn One Click, sign on to one of 17 speedy international servers and view your favorite global content from anywhere.

Express VPN (Windows, Mac, Android, iOS)

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Easy-to-use Express VPN is quick to set up and very reliable. If your work blocks social media sites like Facebook and Twitter, you can easily bypass these restrictions with this streamlined app. Try it for free for seven days, and then you can upgrade to a paid account.

Hola Free VPN (Windows, Mac, Android, iOS)

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Say hello to secure VPN connections with Hola Free VPN. You'll be able to shop from foreign Amazon stores, bid on international eBay sites, access Netflix's geo-restricted library, and much more. Try it for free for seven days. If you're not ready to commit, you can get many of the same features from the free Hola Better Internet extensions for Chrome and Firefox.

Private Internet Access (Windows, Mac, Android, iOS)

Set up your own secure tunnel for surfing with one of the best VPN providers, Private Internet Access. Known for being reliable and discrete, PIA does not keep a log of your activity, nor does it discriminate against the types of traffic or protocols you use. The app supports Windows, Mac, and Android, and the companion OpenVPN Connect for iOS, PIA, starts at $3.33 per month.

Joshua Rotter is a copy editor for Download.com and covers iOS.