Clear, robust standards for clean hydrogen products will crucially enable green molecules to displace fossil fuels and guarantee that fuel switching actually reduces carbon emissions in heavy industry and transport. The potential for hydrogen to play a role in reducing emissions depends on its production pathway: hydrogen produced with renewable power (green hydrogen) can achieve near-zero emissions, while hydrogen produced from natural gas (blue hydrogen) can only achieve true “clean” status depending on effective control of upstream methane leakage and carbon capture methods.