Tropospheric ozone formation depends on the emissions of volatile organic compounds (VOC) and nitrogen oxides (NO
x
). In megacities, abundant VOC and NO
x
sources cause relentlessly high ozone episodes, affecting a large share of the global population. This study uses data from the Ozone Monitoring Instrument for formaldehyde (HCHO) and nitrogen dioxide (NO
2
) as proxy data for VOC and NO
x
emissions, respectively, with their ratio serving as an indicator of ozone sensitivity. Ground-level ozone (O
3
) reanalysis from the Copernicus Atmosphere Monitoring is used to assess the O
3
trends. We evaluate changes from 2005 to 2019 and their relationship with the warming environment in 41 megacities worldwide, applying seasonal Mann-Kendall, trend decomposition methods, and Pearson correlation analysis. We reveal significant increases in global HCHO (0.1 to 0.31 × 10
15
mol cm
−2
year
−1
) and regionally varying NO
2
(−0.22 to 0.07 × 10
15
mol cm
−2
year
−1
). O
3
trends range from −0.31 to 0.70 ppb year
−1
, highlighting the relevance of precursor abundance on O
3
levels. The strong correlation between precursor emissions and increasing temperature suggests that O
3
will continue to rise as climate change persists.