Tails is part of the [Tor Project](https://torproject.org/).
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No.Tails provides upgrades every six4 weeks, thatwhich are thoroughly tested to make sure that no security feature or configuration gets broken. Updating add-ons in <span class="application">Tor Browser</span> might break the security built in Tails.
As explained in our documentation about [[the fingerprint of *Tor Browser* in Tails|doc/anonymous_internet/Tor_Browser#fingerprint]], Tails provides anonymity by making it difficult to distinguish a particular user amongst all the users of *Tor Browser* (either in Tails or on other operating systems).
For example, the user-agent string of *Tor Browser* includes <em>Windows NT</em> but this value preserves your anonymity even if you run Windows NT. On the other hand, changing this value makes you distinguishable from other users of *Tor Browser* and, as a consequence, weakens your anonymity.
This second synchronization is made by sending HTTPS queries through Tor to several websites and deducing a correct time from their answers. You can see the list of websites that Tails can connect to in *[[!tails_gitweb config/chroot_local-includes/etc/default/htpdate.pools desc="/etc/default/htpdate.pools"]]*.
You can install `youtube-dl` as [[Additional Software|doc/persistent_storage/additional_software]]. *youtube-dl* allows downloading videos from more than [700 websites](https://github.com/rg3/youtube-dl/blob/master/docs/supportedsites.md).