📰 September 2025: SEO in Flux

September 2025 will be remembered as one of the most eventful months in SEO in recent years.

From the completion of Google’s August spam update to crawling glitches, experimental AI search variants, and brand-new research into Generative Engine Optimisation, the landscape has shifted fast.

Barry Schwartz summed it up bluntly on Search Engine Roundtable: “Volatility was through the roof this month – rankings yo-yoed, reporting broke, and Google gave us more questions than answers.”

Here’s the full picture of what happened in September, why it matters, and what SEOs should do now.

🚨 Google’s August 2025 Spam Update Concludes

Google confirmed on 22 September that the August 2025 spam update had fully rolled out. The update began on 26 August and took nearly four weeks to finish, making it one of the longer spam updates in recent memory.

According to Search Engine Land, many affiliate sites and auto-generated content farms were hardest hit. Barry Schwartz noted, “Thin content and manipulative tactics were squarely in the firing line. This was Google cleaning house.”

For SEOs, the lesson is clear: if your content adds no value beyond duplication, expect it to be filtered. Google’s John Mueller reiterated, “Spam updates aren’t about creativity — they’re about weeding out abuse at scale.”

🕷️ Crawl Issues and “Preferred Sources” Testing

SEOs reported crawling disruptions in September, with Search Console showing uneven fetches across large sites. Google acknowledged problems and said fixes were in progress. For e-commerce and publishers, this meant pages sitting in limbo – crawled but not indexed for weeks.

Adding to the mix, Google began quietly trialling “Preferred Sources” in the US and UK. This feature allows site owners to nominate trusted pages as their authoritative resources. Early testers noted mixed results. As one SEO put it, “It’s promising, but right now it feels like shouting into the void.”

🤖 AI Search Experiments: Darksteel, Products, AI Mode

September also brought a wave of AI search experiments. Reports surfaced of an internal Google test called “Darksteel”, a potential new variant of AI search. At the same time, SEOs spotted AI-generated product summaries appearing in some shopping results, and even a “translate conversation” feature embedded in AI Mode for multilingual queries.

Perhaps the biggest stir came from rumours that AI Mode could become the default search experience. Google executives denied this, but the speculation caused anxiety. One SEO joked on Twitter/X, “Every time we stabilise, someone yells AI Mode is going default. My blood pressure can’t take it.”

Whether or not AI Mode becomes the norm, these experiments underline Google’s willingness to reshape the SERP experience at pace.

📉 The num=100 Parameter Removal

A more technical but equally disruptive change came when Google quietly disabled the num=100 search parameter, which let users request 100 results per page. The fallout was immediate: many SEOs saw impressions in Search Console plummet overnight.

Barry Schwartz explained, “This wasn’t your rankings dropping. It was the reporting shifting. The num=100 parameter inflated impressions by surfacing results that most users never saw.”

Takeaway: don’t panic if impressions fell in September. Check clicks, conversions, and rankings to confirm if visibility actually changed.

📚 Generative SEO Research Published

September was also a landmark month for academic work on generative SEO. Three notable papers hit arXiv:

• Beyond Keywords: Introduced the CC-GSEO-Bench framework, arguing for measuring content by generative influence rather than rankings. Quote: “SEO should evolve from a keyword lens to a content-impact lens.”
• Generative Engine Optimisation (GEO): Found AI search tends to prefer third-party mentions and citations over brand self-promotion. “In AI answers, earned media matters more than owned media.”
• Role-Augmented G-SEO: Proposed intent-driven modelling, helping creators align content to roles AI assigns in conversations.

For practitioners, the key is not to chase hacks but to structure content for clarity, citation, and usefulness.

📈 Industry Chatter and Ongoing Volatility

Across forums and Slack groups, SEOs vented about ongoing instability. Rankings swung up and down even after the spam update ended. Some blamed lingering bugs, others speculated about AI tests. One agency lead summed it up: “September was a rollercoaster – just when you thought you’d recovered, another test pulled the rug out.”

Yet amid the chaos, a consistent theme emerged: evergreen, authoritative content continued to perform best.

✅ What SEOs Should Do Now

• Audit shallow content: Expand thin posts into guides with depth, examples, and data.
• Check crawling: Use GSC and logs to spot missed fetches. Fix rendering and server issues.
• Review impressions vs clicks: Drops may be reporting artefacts, not penalties.
• Experiment with structured answers: FAQs, TL;DRs, and concise summaries aid retrieval in AI Overviews.
• Track ROI: Focus on revenue, leads, and engagement, not vanity metrics.

🧠 Final Thought

September 2025 reminded SEOs of one eternal truth: the ground is always moving. Spam updates,  crawl bugs, and AI experiments all reshaped the field – but the winners stayed the same.

Clear, crawlable, authoritative content built for users endures, no matter how flashy the changes in AI search appear. Ignore shortcuts, double down on fundamentals, and treat AI surfaces as another channel, not a replacement.

📌 David Roche on September SEO

David Roche says: “September felt messy, but the playbook didn’t change: build better answers, prove your authority, and stay calm when Google shakes the table.”

📣 What the Experts Are Saying

• Aleyda Solís: “LLMs answers also rely on grounding … which means SEO is vital for it.”
• Barry Schwartz: “Volatility was through the roof this month — rankings yo-yoed, reporting broke, and Google gave us more questions than answers.”
• Industry Analysts: “In AI answers, earned media matters more than owned media. Citations drive inclusion.”

❓ FAQs

How did the August 2025 spam update impact SEO?

Thin, manipulative content was hit hardest. Authoritative sites with clear value generally improved.

Why did Search Console impressions drop in September?

The removal of the num=100 parameter caused inflated impressions to disappear. Rankings may be unaffected.

Is AI Mode becoming the default Google search?

Despite rumours, Google has denied making AI Mode the default. It remains experimental.