Tails is a complete sandbox environment which doesn't leak information out to your normal computing environment. It doesn't store any information, so no cookies, logs or cache are retained. Sending network traffic via Tor means that your data can't be eavesdropped on.

It is a solid Linux distro that focuses on protecting customers' privacy and anonymity. It runs on a Live USB flash drive or DVD so there is no trace will be left behind after using it. It comes with software that focuses on security and privacy, such as Tor browser, VeraCrypt, KeePassX, GnuPG, Monkeysign, GtkHash, and more. And if you install Tails on a USB flash drive, you have the option to create a persistent encrypted volume to save your data and to install additional software - if you have enough free space on the USB flash drive. The installation of Tails is not as simple as the installation of other popular Linux distros (Ubuntu, Mint, Debian, etc.), but the official website of Tails has a step-by-step and easy-to-follow instruction on Tails installation. There is also an automatic upgrade mechanism to upgrade your USB stick to newer versions. If you are not ready to run Tails from either a USB stick or DVD, you can also install and run it in a virtual machine such as VirtualBox. Overall, it is a superb Linux distro and it is open source.

Tails leaves no trace on the host computer so I am able to work on a computer that I don't own without leaving data behind. The small size of the operating system means it can easily fit on a flash drive and if you have some free space left on the drive, you can enable persistence to allow you to save files and settings.