AI Visibility Index: September 2026

ChatGPT cut Reddit's share of its citations in half over the summer. Across a fixed panel of 32 major web sources, Reddit fell from 28.5% of ChatGPT's citations in July to 12.1% in September. Google's AI Overviews barely moved. Every engine now has a different favourite source, and the gap between them is widening.

Nik

Co-founder at AskWatch.ai

Published
30 September 2026

AI Visibility Index, September 2026, key numbers: 12.1% Reddit's share of ChatGPT citations in September, down from 28.5% in July; 20.2 pp Citation share that changed hands in ChatGPT, August to September; 1.2 pp The same for Google AI Overviews, the most stable engine; 31.5% Wikipedia's average share across six engines, the #1 source.Download PNG

What moved this month

ChatGPT is moving away from forums and toward reference sites. User-generated sources (Reddit, YouTube, Quora, LinkedIn and the like) went from 39.6% of ChatGPT's panel citations in July to 21.7% in September. Reference sites (Wikipedia, NIH, Mayo Clinic, Healthline, Britannica) rose from 44.8% to 59.5%.
Google AI Overviews is the most stable engine by far. Only 1.2 percentage points of citation share moved between panel domains from August to September. Three quarters of its citations still go to user-generated sources, with YouTube, TikTok and Reddit on top.
Gemini is doing the opposite of ChatGPT. Reddit's share of Gemini citations rose from 27.0% to 33.6% over the same three months, and Gemini is the most concentrated engine: three domains take 85% of its citations.
Perplexity is shifting toward commerce and news. Commerce sources (Amazon, TripAdvisor, Yelp, NerdWallet) doubled from 4.1% to 7.9% of Perplexity's citations; media sources rose from 2.3% to 4.2%.
Engines agree on the top of the list and disagree on everything else. AI Overviews and AI Mode share an identical top 10; ChatGPT shares only 7 of its top 10 with any other engine. Gemini and Copilot overlap with the others on 6 of 10.

The Reddit divergence

Reddit's share of each engine's citations to the panel, three monthly snapshots.

Reddit's share of AI citations by engine, Jul to Sep 2026: ChatGPT fell from 28.5% to 12.1%, Gemini rose from 27.0% to 33.6%, Google AI Overviews held near 19.5%.Download PNG

Reddit's share of panel citations by engine and month
	ChatGPT	AI Overviews	AI Mode	Perplexity	Gemini	Copilot
Jul	28.5%	20.4%	23.2%	13.5%	27.0%	2.0%
Aug	22.5%	20.1%	21.5%	19.5%	28.7%	0.7%
Sep	12.1%	19.5%	18.8%	22.3%	33.6%	0.6%

Restless engines, settled engines

Citation turnover: how many percentage points of citation share moved between panel domains from one month to the next. Zero would mean every source kept exactly its share.

Citation turnover by AI engine, month over month: ChatGPT 9.2 then 20.2 pp, AI Overviews 3.3 then 1.2 pp, AI Mode 2.8 then 6.4 pp, Perplexity 17.7 then 8.9 pp, Gemini 4.4 then 7.2 pp, Copilot 8.3 then 2.5 pp.Download PNG

Citation turnover by engine, percentage points
	ChatGPT	AI Overviews	AI Mode	Perplexity	Gemini	Copilot
Jul to Aug	9.2 pp	3.3 pp	2.8 pp	17.7 pp	4.4 pp	8.3 pp
Aug to Sep	20.2 pp	1.2 pp	6.4 pp	8.9 pp	7.2 pp	2.5 pp

Perplexity was the volatile one in August (17.7 pp) and calmed down in September (8.9 pp). ChatGPT went the other way: 9.2 pp in August, then 20.2 pp in September, the single largest monthly reshuffle in the panel. Copilot and AI Overviews stayed under 3 pp.

Six engines, six diets

Panel domains grouped into five source types. Same panel, same month, six very different answers.

What each AI engine cites by source type, September 2026: ChatGPT user-generated 21.7%, reference 59.5%, media 2.8%, commerce 3.9%, brand 12.2%; AI Overviews user-generated 74.9%, reference 19.3%, media 1.4%, commerce 2.5%, brand 1.9%; AI Mode user-generated 67.7%, reference 24.8%, media 2.3%, commerce 2.8%, brand 2.4%; Perplexity user-generated 42.3%, reference 41.7%, media 4.2%, commerce 7.9%, brand 3.9%; Gemini user-generated 52.4%, reference 40.3%, media 2.7%, commerce 0.6%, brand 4.0%; Copilot user-generated 11.9%, reference 58.5%, media 2.6%, commerce 21.3%, brand 5.7%.Download PNG

Data behind this chart

Panel citations by source type, September 2026
	User-generated	Reference	Media	Commerce	Brand
ChatGPT	21.7%	59.5%	2.8%	3.9%	12.2%
AI Overviews	74.9%	19.3%	1.4%	2.5%	1.9%
AI Mode	67.7%	24.8%	2.3%	2.8%	2.4%
Perplexity	42.3%	41.7%	4.2%	7.9%	3.9%
Gemini	52.4%	40.3%	2.7%	0.6%	4.0%
Copilot	11.9%	58.5%	2.6%	21.3%	5.7%

Source types: user-generated = Reddit, YouTube, Quora, Stack Overflow, LinkedIn, Medium, GitHub, TikTok · reference = Wikipedia, Britannica, Investopedia, Healthline, Mayo Clinic, WebMD, NIH · media = NYT, Forbes, BBC, TechCrunch, CNET · commerce = Amazon, G2, TripAdvisor, NerdWallet, Yelp, Capterra · brand = HubSpot, Shopify, Semrush, Zapier, Apple, Microsoft.

ChatGPT's summer diet change

The user-generated block shrank from 40% to 22% while the reference block grew from 45% to 60%. Brand sites grew from 8% to 12%.

ChatGPT citations by source type, Jul to Sep 2026: user-generated sources fell from 39.6% to 21.7%, reference sites rose from 44.8% to 59.5%.Download PNG

ChatGPT panel citations by source type and month
	User-generated	Reference	Media	Commerce	Brand
Jul	39.6%	44.8%	3.8%	3.9%	7.8%
Aug	37.8%	44.7%	4.0%	4.6%	8.9%
Sep	21.7%	59.5%	2.8%	3.9%	12.2%

Copilot is the outlier at the other end: 58.5% reference and 21.3% commerce (mostly Amazon), with user-generated sources under 12%. If Copilot answers questions about your product, Amazon listings and Wikipedia matter more than Reddit threads.

The citation leaderboard

AI Visibility Score is a domain's average share of citations across all six engines. Change is September against August; up and down count the engines where the domain's share moved by more than 5%.

Most cited sources in AI search, September 2026, by AI Visibility Score: 1. wikipedia.org 31.5%, 2. youtube.com 19.7%, 3. reddit.com 17.8%, 4. amazon.com 4.2%, 5. nih.gov 3.9%, 6. apple.com 3.6%, 7. linkedin.com 2.7%, 8. tiktok.com 2.7%, 9. healthline.com 1.7%, 10. forbes.com 1.6%.Download PNG

Top 20 sources by AI Visibility Score, September 2026
Domain	Type	Score Sep	Aug	Jul	Δ pp	Δ %	Up / down
1. wikipedia.org	Reference	31.5	28.8	28.5	+2.7	+9.3%	4 / 0
2. youtube.com	User-generated	19.7	22.4	24.6	−2.7	−12.0%	1 / 3
3. reddit.com	User-generated	17.8	18.8	19.1	−1.0	−5.3%	2 / 3
4. amazon.com	Commerce	4.2	3.9	2.6	+0.3	+8.0%	2 / 2
5. nih.gov	Reference	3.9	2.8	2.2	+1.2	+41.8%	4 / 2
6. apple.com	Brand	3.6	3.2	3.0	+0.5	+15.2%	3 / 0
7. linkedin.com	User-generated	2.7	2.8	2.6	−0.1	−4.7%	2 / 3
8. tiktok.com	User-generated	2.7	2.9	3.1	−0.2	−8.5%	1 / 2
9. healthline.com	Reference	1.7	1.9	2.1	−0.2	−9.8%	1 / 2
10. forbes.com	Media	1.6	1.8	1.8	−0.3	−13.8%	1 / 5
11. quora.com	User-generated	1.4	1.6	1.8	−0.3	−16.0%	3 / 2
12. mayoclinic.org	Reference	1.3	1.3	1.4	+0.0	+2.2%	2 / 1
13. tripadvisor.com	Commerce	1.1	1.2	0.9	−0.1	−6.0%	0 / 3
14. britannica.com	Reference	1.0	1.0	1.0	+0.1	+5.5%	2 / 1
15. webmd.com	Reference	1.0	1.1	1.1	−0.0	−3.6%	1 / 1
16. microsoft.com	Brand	0.9	0.8	0.8	+0.2	+23.1%	2 / 1
17. medium.com	User-generated	0.7	0.8	0.8	−0.1	−10.9%	0 / 5
18. nerdwallet.com	Commerce	0.5	0.5	0.4	+0.0	+1.9%	2 / 2
19. cnet.com	Media	0.4	0.5	0.5	−0.0	−8.1%	1 / 2
20. nytimes.com	Media	0.4	0.3	0.3	+0.1	+15.7%	3 / 1

Gained the most share

Domains with a score of 0.5 or more

nih.gov+41.8%
microsoft.com+23.1%
apple.com+15.2%
wikipedia.org+9.3%
amazon.com+8.0%
britannica.com+5.5%

Lost the most share

Domains with a score of 0.5 or more

quora.com−16.0%
forbes.com−13.8%
youtube.com−12.0%
medium.com−10.9%
healthline.com−9.8%
tiktok.com−8.5%

Where the engines part ways

The number of domains two engines share in their top-10 lists, September 2026.

Domains shared between the top-10 cited sources of two AI engines, September 2026: ChatGPT and AI Overviews 7, ChatGPT and AI Mode 7, ChatGPT and Perplexity 7, ChatGPT and Gemini 7, ChatGPT and Copilot 7, AI Overviews and AI Mode 10, AI Overviews and Perplexity 8, AI Overviews and Gemini 6, AI Overviews and Copilot 6, AI Mode and Perplexity 8, AI Mode and Gemini 6, AI Mode and Copilot 6, Perplexity and Gemini 6, Perplexity and Copilot 6, Gemini and Copilot 6.Download PNG

Shared domains between engines' top-10 lists
	ChatGPT	AI Overviews	AI Mode	Perplexity	Gemini	Copilot
ChatGPT	—	7	7	7	7	7
AI Overviews	7	—	10	8	6	6
AI Mode	7	10	—	8	6	6
Perplexity	7	8	8	—	6	6
Gemini	7	6	6	6	—	6
Copilot	7	6	6	6	6	—

Three sites, most of the answer

Share of each AI engine's citations taken by its top three domains, September 2026: ChatGPT 65.4%, AI Overviews 76.1%, AI Mode 75.8%, Perplexity 70.8%, Gemini 85.3%, Copilot 70.1%.Download PNG

Share of citations taken by each engine's top three domains
	ChatGPT	AI Overviews	AI Mode	Perplexity	Gemini	Copilot
Top three domains	65.4%	76.1%	75.8%	70.8%	85.3%	70.1%

Gemini is the most concentrated engine; ChatGPT the least. For a brand, this means the same three sites decide most of what Gemini says, while ChatGPT spreads its attention wider.

Zooming in: five markets, five maps

Twenty more domains look inside five markets. Each niche is a closed panel of its own, so shares add up to 100% within it. Score is the average share across six engines in September; leads is the number of engines where the domain is the niche's #1 source.

Citation turnover inside five niches by AI engine, September 2026: Health ChatGPT 16.3, AI Overviews 0.8, AI Mode 4.6, Perplexity 3.9, Gemini 4.1, Copilot 1.3; Finance ChatGPT 8.1, AI Overviews 1.3, AI Mode 3.8, Perplexity 6.3, Gemini 4.9, Copilot 3.4; Software & B2B ChatGPT 3.8, AI Overviews 2.3, AI Mode 5.9, Perplexity 1.2, Gemini 2.8, Copilot 6.5; Shopping ChatGPT 7.6, AI Overviews 2.9, AI Mode 5.7, Perplexity 2.0, Gemini 1.6, Copilot 1.5; Travel ChatGPT 3.9, AI Overviews 1.3, AI Mode 4.4, Perplexity 3.2, Gemini 3.7, Copilot 2.6 percentage points.Download PNG

Citation turnover inside each niche, percentage points
	ChatGPT	AI Overviews	AI Mode	Perplexity	Gemini	Copilot
Health	16.3	0.8	4.6	3.9	4.1	1.3
Finance	8.1	1.3	3.8	6.3	4.9	3.4
Software & B2B	3.8	2.3	5.9	1.2	2.8	6.5
Shopping	7.6	2.9	5.7	2.0	1.6	1.5
Travel	3.9	1.3	4.4	3.2	3.7	2.6

Health is where ChatGPT is rewriting its sources. Inside the seven health sites, 16.3 pp of ChatGPT's citation share moved in one month, against 0.8 pp in AI Overviews. NIH gained 3.5 pp of the niche and now leads in ChatGPT and AI Mode; Healthline still leads in AI Overviews, Perplexity and Gemini.

Finance has one owner. Forbes takes 52.7% of niche citations and is the #1 finance source in all six engines. NerdWallet is a distant second at 15.6%.

In software, review media beat review marketplaces. TechRadar and PCMag together hold 70% of the niche; G2, Capterra and Software Advice combined hold 18.5%. Product Hunt is cited almost never (0.4%).

Trustpilot is a top-two shopping source. At 23.7% of niche citations Trustpilot sits just behind Amazon (26.8%) and leads in ChatGPT and Gemini. Walmart (18.1%) is cited more than eBay and Best Buy combined.

Travel is a two-horse race. TripAdvisor (36.6%) and Booking.com (34.6%) split the niche; TripAdvisor leads in four engines, Booking.com in ChatGPT and Gemini.

Health

Health: niche share, change and engines led
Domain	Score	Δ pp	Leads
nih.gov	26.8%	+3.5	2
healthline.com	19.5%	−1.8	3
clevelandclinic.org	13.9%	−0.2	1
mayoclinic.org	12.1%	−0.5
webmd.com	11.7%	−0.7
drugs.com	9.2%	+0.2
medicalnewstoday.com	6.9%	−0.7

Finance

Finance: niche share, change and engines led
Domain	Score	Δ pp	Leads
forbes.com	52.7%	−2.0	6
nerdwallet.com	15.6%	+1.0
investopedia.com	8.9%	+0.2
bankrate.com	7.1%	+0.2
cnbc.com	7.0%	+0.6
fool.com	6.8%	0.0
bloomberg.com	2.0%	0.0

Software & B2B

Software & B2B: niche share, change and engines led
Domain	Score	Δ pp	Leads
techradar.com	38.5%	−1.4	2
pcmag.com	31.9%	−0.7	4
g2.com	10.5%	+0.5
capterra.com	5.4%	+0.5
zapier.com	4.9%	+0.4
softwareadvice.com	2.6%	0.0
semrush.com	2.1%	+0.2
hubspot.com	2.0%	+0.2
gartner.com	1.7%	+0.1
producthunt.com	0.4%	0.0

Shopping

Shopping: niche share, change and engines led
Domain	Score	Δ pp	Leads
amazon.com	26.8%	−0.7	4
trustpilot.com	23.7%	+1.8	2
walmart.com	18.1%	−0.1
ebay.com	10.3%	−0.7
rtings.com	8.3%	+0.8
cnet.com	7.0%	−0.6
bestbuy.com	5.8%	−0.5

Travel

Travel: niche share, change and engines led
Domain	Score	Δ pp	Leads
tripadvisor.com	36.6%	−0.2	4
booking.com	34.6%	−1.5	2
expedia.com	15.2%	+0.2
yelp.com	9.2%	+0.5
lonelyplanet.com	4.4%	+1.0

Press kit

If you only read three lines

Reddit's share of ChatGPT citations fell from 28.5% to 12.1% between July and September 2026, while its share of Gemini citations rose from 27.0% to 33.6%.
ChatGPT reshuffled 20.2 percentage points of citation share in September; Google AI Overviews reshuffled 1.2.
Wikipedia is the single most-cited source in AI search, with 31.5% of panel citations averaged across six engines.

Quotable

“A brand that optimised for Reddit in spring got half the ChatGPT visibility it expected by autumn. The engines are not converging on one idea of a trustworthy source; they are drifting apart.”
Nik, Co-founder at AskWatch.ai

“Google AI Overviews is the one engine where last month's citation map still works this month. Everywhere else, the ground moves every four weeks, which is why we track this monthly.”
Nik, Co-founder at AskWatch.ai

“Copilot is quietly the most commerce-friendly engine: one in five of its citations goes to a shopping or review site. If you sell on Amazon, Copilot already knows you.”
Nik, Co-founder at AskWatch.ai

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