For most of the summer, Reddit was one of ChatGPT Search's most-cited domains. In the second week of August 2026, that share fell off a cliff, and the firm tracking it still can't fully explain why.
The scale is exact, not estimated. Reddit averaged a 3.83% share of ChatGPT Search citations from July 18 through August 7, then collapsed to a 0.52% average between August 14 and 17 — an 86.4% relative drop, with the sharp break landing inside a single day.
It wasn't every AI platform, and it wasn't sudden everywhere
The same tracking shows the collapse was specific to ChatGPT. Reddit's share of Google AI Overviews citations slid only from 2.37% to 2.10% over the same window — an 11.3% relative decline, moving gradually rather than breaking in one day. Google AI Mode fell further, from 2.22% to 1.54%, a 30.5% decline, but that traces back to a step change in late July, not the August 14 cliff. Whatever happened, it happened almost entirely inside ChatGPT.
The timing lines up with a search-behavior change six days earlier
On August 8, ChatGPT Search started scoping roughly 1 in 6 of its background searches to a single domain using the site: operator, up from about 1 in 280 the week before. The average number of searches ChatGPT runs per response nearly doubled the same day. Reddit's citation share started sliding that same day, six days before the steeper collapse.
The tracking firm's own read of that shift is that it's additive, not a swap: domain-scoped searches layered on top of ChatGPT's normal web search rather than replacing it, since the number of searches per response went up instead of staying flat. That's a meaningfully different story than "ChatGPT stopped searching the open web" — it's now searching wider, and for some domains, deeper.
What neither report claims is a confirmed cause for Reddit specifically. The firm is explicit that its own charts show when each change happened, not why, and that a data-collection issue on its end can't be fully ruled out — a more honest position than most of the coverage that ran with the headline number that week.
The practical read for anyone doing GEO work isn't "stop investing in Reddit." It's that citation share on a single platform can move 86% in four days for reasons even the firm tracking it won't fully commit to — which is the argument for treating AI visibility as something to monitor continuously, not a channel you set up once and revisit at the next planning cycle.