Ahimsa is shared by the Indian traditions, but they do not mean the same thing by it, and Jainism is where the principle is carried to its logical end.
Jain doctrine holds that souls inhabit not only animals but plants, and elemental bodies in earth, water, fire and air, graded by the number of senses each possesses. Harm to any of them binds karma, understood in Jainism as a physical substance adhering to the soul rather than as a moral ledger. The consequences are worked out in detail. Jain monastics sweep the ground ahead of them with a soft brush, filter water, avoid travelling at night when insects cannot be seen, neither light nor extinguish fire, and in the Digambara tradition eat once a day from cupped hands. Lay Jains keep a lesser vow: strict vegetarianism that also excludes root vegetables, because uprooting a plant kills it along with the organisms in the soil, and often excludes honey and figs. Many also avoid eating after dark.
The occupational consequence is historically large. Agriculture involves unavoidable killing, so Jains moved into trade, finance and later the gem and textile businesses, and the community's commercial position in western India is a direct result of a doctrine about insects.
Hindu ahimsa is a virtue held in tension with duty. The Bhagavad Gita is framed as an argument about exactly that tension, with Krishna instructing Arjuna that his obligation as a warrior stands, which is how Hindu tradition sustains both renunciant nonviolence and a martial ethic without treating the pair as a contradiction.
Buddhist practice makes non-harming the first precept and does not extend it to plants. Under the traditional monastic rule a monk may eat meat if the animal was not killed specifically for him, which is why Theravada monastics in Thailand and Sri Lanka are commonly not vegetarian while Mahayana monastics in China commonly are.