The Forerunners were a bipedal species resembling humans in overall shape, though they were larger in stature. Before their first mutation, they were tall and slender, and possessed patches of fine, purple-pink or white fur on the top of their heads, along their nape and shoulder area, as well as the backs of their hands.[24] Their facial features were similar to those of humanity, and they were capable of making analogous expressions, but this changed as they mutated to their higher forms, which characteristically had stiffer facial muscles and a more limited ability to convey emotions.[25] The Forerunners also had a genetic code that was remarkably similar to humans, though they were not known to be genetically related.[26]
Their skin color ranged greatly, including gray, black, blue, pink, or a mixture thereof. The number of fingers Forerunners possessed seems to have varied according to their rate and form; Lifeworkers, for example, were known to have seven fingers,[27] while Bornstellar's later form, based on a mixed pattern, had six fingers.[28]
All Forerunners wore personal body armor which featured many functions, including protection from harm and medical assistance. This armor also eliminated their need to sleep, and made their lifespans basically indefinite; the Librarian, for example, was over eleven thousand years old by 100,000 BCE.[29]