You can help Tails! The [[MAC address spoofing|contribute/design/MAC_address]] feature is ready for testing. This feature prevents geographical tracking of your network devices (and by extension, you) by randomising their [[!wikipedia MAC addresses]].
Every network device (wired, Wi-Fi/wireless, 3G/mobile) has a [[!wikipedia MAC address]], which is a unique identifier used to address them on the local network. Broadcasting a unique identifier in this manner introduce a couple of potential privacy issues for Tails users. Geographical location tracking is the main one: observing a MAC address at a particular location and time ties the corresponding device to the same location and time. If the real identity of the device's owner is known, their movements can be determined. To prevent this one can temporarily change the MAC address to something random at each boot, which is referred to as "MAC address spoofing".
Download the latest test ISO from [build_Tails_ISO_devel](http://nightly.tails.boum.org/build_Tails_ISO_devel/). **Keep in mind that this is a test image.** Do not use it for anything else than testing this feature.
MAC spoofing is enabled by default in this test ISO. You can change this with a [[startup option|doc/first_steps/welcome_screen]]. The (preliminary) MAC spoofing documentation tries to explain situations where it actually may be a bad idea to keep this option enabled. However, as this is just a test version we of course urge you to not use it for anything serious, and if possible, to test both to enable and disable the option.
For any MAC spoofing-related issues you experience using this test ISO, please include the output from the following commands when reporting it to us (note: it requires setting an [[doc/first_steps/welcome_screen/administration_password]]):