If you read our Mid-September 2026 round-up, you’ll remember we closed by saying the back half of the month was going to be noisy. It was noisier than expected. Google launched its fourth spam update of the year, AI Overviews quietly swallowed another chunk of click-through traffic, ChatGPT lost its 50% market-share crown for the first time since launch, and the EU and UK both moved on search data in ways that could reshape AI search competition inside twelve months.
Here’s what actually happened between 21 September and 5 October 2026, what it means, and what to do this week.
1. The headline event: Google September 2026 Spam Update
Google began rolling out the September 2026 Spam Update at 09:15 PDT on 24 September. It’s the fourth spam update of the year (after March, June and August) and is being rolled out globally, in every language.
Two things make this one different:
- The two-week window. Every other 2026 spam update was estimated at “a few days” and none finished slower than 2 days and 16 hours. This one was given up to two weeks from the start – and as of 2 October, Google’s Search Status Dashboard still shows it as active.
- It arrived in phases. The first wave of volatility hit between 25–27 September. A second, equally large wave was reported on 30 September and 1 October by Barry Schwartz, Glenn Gabe and other trackers. If your rankings moved on either of those dates, it was almost certainly this update.
How this update compares to the rest of 2026
| Spam Update | Start date | Rollout duration |
|---|---|---|
| March 2026 | 24 March | 19 hours 30 minutes |
| June 2026 | 24 June | 2 days 1 hour |
| August 2026 | 18 August | 2 days 16 hours |
| September 2026 | 24 September | Ongoing (expected ~8 October) |
What to do: Don’t finalise an impact analysis until Google confirms the rollout is complete. Pull your Search Console data from 24 September onwards, filter by page type and query cluster, and keep a note of any site changes (deployments, redirects, content pushes) you shipped in that window so you don’t blame or credit the wrong thing.
2. AI search is now genuinely eating Google – and ChatGPT
Three numbers landed in the last fortnight that I’d pin to the wall if I were running an in-house SEO team:
- Google AI Overviews now appear on 80% of branded queries, up from 26% earlier in the year.
- Google AI Mode has crossed 1 billion monthly users, per Google’s own figure reported on 29 September – a number that rivals ChatGPT’s estimated 1 billion MAUs from May.
- ChatGPT’s share of the generative AI chatbot market slipped below 50% for the first time in September, finishing the month at 52.1%, with Gemini climbing to 26.9%.
ChatGPT market share through 2026
Monthly share of the generative AI chatbot market. ChatGPT held above 65% through Q1, lost ground to Gemini all summer, and dipped below 50% for the first time in July before stabilising.
Source: First Page Sage / Sensor Tower, October 2026 report.
Where that lost market share went
| AI assistant | Market share (Sep 2026) | Quarterly user growth |
|---|---|---|
| ChatGPT | 52.1% | +5% |
| Google Gemini | 26.9% | +10% (approx.) |
| Microsoft Copilot | 1.32% | Highest reading of 2026 |
| Perplexity | 1.9% | Down from 5.3% in Jan |
| Claude | (not listed in top table) | +15% (fastest growing) |
The pattern is clear: ChatGPT is still the market leader by a comfortable margin, but the “AI = ChatGPT” era is over. Any AI-visibility tracking programme that only measures ChatGPT is now missing roughly half of the signal.
The one that gave me the biggest pause this fortnight was a separate report that Reddit citations in ChatGPT Search dropped 86% in four days. If you have a strategy that leans on Reddit as a source of AI visibility, go and re-check it – the mix of citation sources is less stable than any of us assumed.
3. Google Search Console: three real changes in two weeks
Search Console had more product news in September than it had in most of H1. Three things worth knowing:
a) Generative AI performance report now worldwide
Google’s Generative AI report in Search Console – showing impressions and clicks from AI Overviews and AI Mode – rolled out globally. If you don’t see it yet, it should appear in the next few days. It’s not perfect (more on that below), but it’s the first time most of us have had any first-party AI-visibility data at all.
b) New multimodal filter for image-based searches
A new filter – sitting under the Web search type – now splits out performance for searches where someone used an image (think Google Lens, Circle to Search). The global rollout began on 24 September and applies to both the standard Search results and the Generative AI reports.
c) Google is fixing a long-running impressions bug
Google has confirmed a logging error that inflated impression counts since 13 May 2025. The fix is now rolling out. Clicks are unaffected. If your impressions suddenly drop in the next few weeks, don’t panic – it’s probably Google’s numbers quietly correcting themselves, not a traffic loss.
A caveat on the AI reporting
An important caveat on this new data: Search Console treats an entire AI Overview as a single block and assigns the same ranking position to every link inside it, regardless of where the link actually appears in the answer. John Mueller acknowledged on Reddit on 16 September that AI Mode and AI Overviews position/impression tracking will “evolve over time” and that there are “edge cases”. Translation: these numbers are directionally useful, not literally correct – don’t build your Q4 reporting around a position-based metric for anything AI yet.
4. The AI Overviews / AI Mode drift continues
The product story keeps moving in one direction: AI Overviews behaving more like AI Mode, and both of them keeping users inside Google rather than sending them to publishers.
- In-text links in AI Overviews now sometimes open AI Mode queries, not the external publisher. Peec AI’s chart showed the share of AI Overviews containing an external in-text link climbing from near zero on 10 September to 26.2% by 20 September. Some of those links go to the web – others pre-fill a new AI Mode conversation and keep the user inside Google.
- AI Mode’s click-out rate is now around 4.5%, versus roughly 24% for traditional search, per analysis published this fortnight.
- Gemini 3.8 Flash launched inside AI Mode, briefly without citations (now fixed), followed by Gemini 3.8 Live.
- Google began testing “practice quizzes” in AI Mode on 2 October – a prompt that carries content from a search result into a pre-filled quiz. Another reason for the user to stay in AI Mode rather than click out.
- Google is testing “Sponsored” text link ads inside AI Mode (spotted 15 September), so the commercial model for AI Mode is quietly being built in public.
Growth of external in-text links in AI Overviews
Daily share of AI Overviews containing an in-text external link, 25 August – 20 September 2026. Source: Peec AI.
Values between 25 Aug and 15 Sep are illustrative based on Peec AI’s reported curve shape – Peec confirmed the near-zero baseline and the 26.2% peak on 20 September.
A separate randomised field study published this fortnight found Google’s AI search features reduced external click referrals and that users forced into AI Mode were more likely to try Bing, DuckDuckGo or Yahoo. Removing AI Overviews increased external clicks without a measurable decline in user satisfaction. That’s a difficult data point for Google to carry around.
5. Regulators actually moved
Two regulatory stories that matter more than they look:
- The EU has ordered Google to share search data with rival search engines – and explicitly with AI-powered search tools and chatbots. This is the first time European competition law has treated conversational AI as a search engine for the purposes of data access. Expect challengers (Perplexity, You.com, Mistral-based tools and others) to put in requests before year-end.
- The UK CMA’s consultation on search choice screens closes on 9 October. The proposals would show Android and Chrome users a choice screen at setup and annually, and AI assistants such as ChatGPT and Perplexity would be eligible for listing. The CMA also wants to cover fair attribution of publisher content. A final decision is expected by the end of 2026.
On the publisher side, Google launched its AI Contribution pilot in Search Console – paying selected publishers when Google judges their content to have “significantly contributed” to an AI response. The payouts are reportedly small. The precedent is not.
6. Quick hits: everything else worth knowing
| Date | Story | Why it matters |
|---|---|---|
| 22 Sep | Google AI Mode vs AI Overviews explainer wave | Industry is finally treating them as two different surfaces to optimise for. |
| 23 Sep | UK CMA publishes search choice screen proposals | AI assistants eligible for the choice screen. Consultation closes 9 October. |
| 24 Sep | September 2026 Spam Update begins | Fourth of the year. Still rolling as of 2 October. |
| 24 Sep | GSC multimodal (image search) filter rolls out | First real visibility into Lens / Circle to Search performance. |
| 25–27 Sep | Wave one of spam update volatility | High volatility reported across all major tracker tools. |
| 28 Sep | “7 AI search myths debunked” data piece | Worth the read if you’re arguing internally about AI search strategy. |
| 29 Sep | TIME: Google quietly made 1bn+ people AI users | AI Mode now at ChatGPT scale, largely by UI nudges. |
| 30 Sep | Yext acquires Flamel.ai | Local paid campaigns across Google, Meta and ChatGPT – multi-location brands take note. |
| 30 Sep – 1 Oct | Wave two of spam update volatility | Second ranking jolt, confirmed by Schwartz & Gabe. |
| 1 Oct | Contentstack launches Canoe (AI visibility tool, free tier) | The “GEO stack” is now crowded enough that free tiers are the entry point. |
| 2 Oct | Google tests practice quizzes in AI Mode | Another on-SERP retention mechanic. |
| 5 Oct | DoubleVerify launches attribution for ChatGPT ads | ChatGPT ads are becoming measurable – expect budgets to follow. |
7. What to do this week
A short, honest to-do list for the next seven days:
- Date-stamp the spam update impact. In Search Console, filter by 24 Sep onwards, compare pages and queries, and resist the urge to decide anything until Google marks the rollout complete (expected around 8 October).
- Note the GSC impressions correction. Expect a drop in impressions over the next few weeks that has nothing to do with your rankings. Tell your stakeholders now.
- Build a fixed AI-visibility prompt set. 20–30 queries, run across ChatGPT, Gemini, Claude and Perplexity. Not just ChatGPT. The Reddit-citation collapse is a reminder of how fast the citation mix shifts.
- Audit your in-SERP presence, not just your rankings. With AI Overviews now covering 80% of branded queries and in-text links sometimes keeping users inside AI Mode, “position 1” is doing less work than it did in Q1.
- If you’re in the UK, respond to the CMA consultation before 9 October. If you publish anything, the attribution rules matter directly to you.
The one-sentence summary of the fortnight: Google’s organic ranking surface got noisier, Google’s AI surface got bigger, and the measurement layer around both is still catching up.
We’ll be back with the next round-up in two weeks. If there’s a specific story from the last fortnight you’d like us to go deeper on – the spam update, AI Contribution payouts, the CMA proposals, or the Reddit-citation shift – leave a comment below.
Sources: Google Search Status Dashboard; Search Engine Roundtable (Barry Schwartz, 24 Sep & 1 Oct 2026); Search Engine Land; Search Engine Journal; TIME (29 Sep 2026); First Page Sage / Sensor Tower (Oct 2026); Ignite Visibility weekly round-up (2 Oct 2026); MarketingProfs AI Update (2 Oct 2026); Peec AI chart (via ALMcorp, 30 Sep 2026); MarTech.org (1 Oct 2026); AgileBrandGuide (1–2 Oct 2026).
