Is the Contigo DualSip Insulated Bottle 24oz truly leakproof in a backpack?

Yes, the bottle is engineered to be 100% leakproof when properly secured. When you press the lid down until you hear the audible click, the seal completely locks out any liquid escaping from both the spout and the internal straw channel. Checking out the Contigo DualSip 24oz will show you the exact lid geometry designed to resist unexpected pressure and motion inside bags. The vacuum-insulated stainless steel also prevents outer condensation, so your electronics and papers remain completely dry throughout your commute.