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We used a one-year long SO₂ flux record, which was obtained using a novel algorithm for real-time automatic processing of ultraviolet (UV) camera data, to characterize changes in degassing dynamics at the Mt. Etna volcano in 2016. These SO₂ flux records, when combined with independent thermal and seismic evidence, allowed for capturing switches in activity from paroxysmal explosive eruptions to quiescent degassing. We found SO₂ fluxes 1.5−2 times higher than the 2016 average (1588 tons/day) during the Etna’s May 16−25 eruptive paroxysmal activity, and mild but detectable SO₂ flux increases more than one month before its onset. The SO₂ flux typically peaked during a lava fountain. Here, the average SO₂ degassing rate was ~158 kg/s, the peak emission was ~260 kg/s, and the total released SO₂ mass was ~1700 tons (in 3 h on 18 May, 2016). Comparison between our data and prior (2014−2015) results revealed systematic SO₂ emission patterns prior to, during, and after an Etna’s paroxysmal phases, which allows us to tentatively identify thresholds between pre-eruptive, syn-eruptive, and post-eruptive degassing regimes.