The safest browser is no browser.
So probably libwww. More seriously, assuming privacy and safety are both merged under 'safety', vanilla Firefox and Chrome are out, along with anything that Microsoft has touched. For individual browsers that are semi-mainstream, probably Tor Browser or Brave's Tor mode (which I don't entirely trust in comparison to the former, for some reason). A better option though would be something like Whonix though, where you essentially have Tor browser in a VM.