What fuel inside the lighter?

The fuel inside a lighter is typically butane, a flammable hydrocarbon gas. Butane is stored in the lighter under pressure, allowing it to remain in liquid form. When the lighter is ignited, the butane vaporizes and mixes with air, creating a combustible mixture that produces a flame. Some lighters may use other fuels, such as lighter fluid, butane remains the most common choice for portable lighters.