The determination of groundwater age can aid characterization of aquifers, providing information on groundwater mixing, flow, volume, and recharge rates. Here we assess a recently discovered groundwater age tracer, Halon-1301. Its performance as an age tracer is assessed against six other well-established, widely used age tracers in 302 groundwater samples. We show Halon-1301 reliably inferred age, thus potentially becoming a useful groundwater age tracer where other tracers are compromised.