  Data scouting, introduced by CMS in 2011, is the use of specialized data
streams based on reduced event content, enabling LHC experiments to record
unprecedented numbers of proton-proton collision events that would otherwise be
rejected by the usual filters. These streams were created to maintain
sensitivity to new light resonances decaying to jets or muons, while requiring
minimal online and offline resources, and taking advantage of the fast and
accurate online reconstruction algorithms of the high-level trigger. The
viability of this technique was demonstrated by CMS in 2012, when 18.8
fb$^{-1}$ of collision data at $\sqrt{s} = 8$ TeV were collected and analyzed.
For LHC Run 2, CMS, ATLAS, and LHCb implemented or expanded similar
reduced-content data streams, promoting the concept to an essential and
flexible discovery tool for the LHC.
