In the vernacular, hardline means taking an intellectual or political position that is extreme and uncompromising. A different sense of the word is treated here.

Hardline is commonly considered to be a more extreme form of straight-edge. The most obvious thing that sets hardline apart is its defence-of-all-life philosophy, which means being both vegan and pro-life. Hardliners typically advocate violence in the furtherance of their beliefs, whereas straight-edge is generally considered to be personal. They also tend to uphold the principle of living naturally, which can encompass everything from organic food to not cutting one's hair. Most hardliners are also religious, generally Christian.