The most protected browser is the Tor Browser as well as the Brave Browser.
The Tor Browser is the most private and secure browser for anonymity and the Brave browser has strong default security and privacy with a user friendly interface.
Firefox browser is highly customizable as well and pretty secure.
The oldest web browser that is still in use is Lynx which was launched in the year 1992 and is a text based web browser.
Graphical web browsers like Mosaic web browser was also developed around the same time as Lynx, but Lynx web browser has continued to be maintained and so that makes it the longest running web browser still in active use.
The Lynx web browser is a customizable, text based web browser that is designed for character cell terminals, meaning that Lynx web browser does not display any graphical content.
The Lynx web browser was created and launched in 1992 as a tool to access the then new World Wide Web in a more accessible way for many people.
And as of now, Lynx continues to be maintained, with active development ensuring it's continued relevance and functionality.
Other oldest web browsers are the WorldWideWeb or Nexus which is the very first web browser that was developed by Tim Berners leee in 1990.
The Mosiac web browser was the first widely popular graphical web browser and was released in the year 1993, which displayed images and text on the same page and was also an ancestor of the Netscape Navigator web browser.
The Netscape Navigator web browser was released in the year 1994 and became the dominant web browser of the 1990s and also introduced features such as JavaScript.
And Opera web browser was a significant web browser that was released in the year of 1995, making Opera browser one of the oldest desktop web browsers.