Definition
Search engine optimization (SEO) is the practice of improving a website so search engines can crawl it, understand it and rank it for the queries its audience uses, with the goal of earning unpaid traffic and visibility. In 2026 the same work also determines whether a site is used as a source by AI search features such as Google AI Overviews, AI Mode, ChatGPT search, Copilot and Perplexity, because those systems retrieve pages through search indexes.
SEO is usually split into four areas. Technical SEO makes pages crawlable, indexable, fast and correctly rendered: robots.txt, sitemaps, canonical tags, JavaScript rendering, and Core Web Vitals (Interaction to Next Paint replaced First Input Delay as a Core Web Vital in March 2024). On-page SEO aligns each page with a search intent through its content, headings, titles and internal links. Off-page SEO builds reputation through backlinks, brand mentions and reviews. Content strategy decides which topics to cover in depth so a site builds topical authority. Google's guidance on helpful, people-first content and the E-E-A-T concept in its rater guidelines (experience, expertise, authoritativeness, trust) describe the qualities Google says its systems try to reward.
What changed is the results page and what happens after it. Google said at I/O in May 2026 that AI Overviews had more than 2.5 billion monthly users and AI Mode more than 1 billion. Comscore measured AI Overviews on 39.4% of US desktop searches in June 2026, up from 25.8% in July 2025. Clicks have become harder to earn: SparkToro's 2024 clickstream study found 58.5% of US Google searches ended without a click, and Pew Research found in 2025 that users clicked a traditional result on 8% of visits to pages with an AI summary versus 15% without one. Rich results also shrank. Google dropped HowTo rich results in 2023, phased out seven more structured data features in 2025, and stopped showing FAQ rich results on May 7, 2026.
Google has added tools to match. Since August 31, 2026, every Search Console property has a generative AI performance report showing impressions in AI Overviews and AI Mode, and a Search generative AI control that lets a site opt out of those features without affecting regular rankings.
The relationship between SEO and GEO is mostly overlap with a different scoreboard. Crawlability, clear structure, specific facts and a credible reputation help a page rank and help it get retrieved and cited. The differences are in measurement and emphasis. SEO tracks rankings, clicks and conversions per keyword. GEO tracks whether a brand is mentioned, cited and described accurately across AI engines for a set of prompts, and it puts more weight on third-party sources (reviews, forums, comparison articles) because AI answers summarize what the web says about a brand, not only what the brand says about itself. Google still handled roughly 90% of tracked worldwide search traffic in 2026 by StatCounter's count, so for most sites traditional SEO remains the foundation that AI visibility is built on.
A practical 2026 SEO program therefore keeps the fundamentals (technical health, intent-matched pages, earned authority) and adds AI-specific checks: whether AI search crawlers can reach key pages, which pages are cited for important prompts, and where AI answers recommend competitors instead. Our GEO vs. SEO comparison breaks down where each discipline starts and stops. Related: AI Overviews and SERP.
Examples of Search Engine Optimization (SEO)
- A B2B software company ranks on page one for 'expense management software' but sees organic clicks fall 30% year over year as AI Overviews expand. Search Console's generative AI report shows its comparison page earning AI Overview impressions, so it adds the page to its AI citation tracking and refreshes its pricing table monthly.
- A recipe site's FAQ rich results disappear on May 7, 2026. Its FAQ markup stays valid, but the expanded listings are gone, so the team shifts effort to recipe structured data, which Google still supports, and to clearer step-by-step passages.
- A local dental chain fixes duplicate location pages, adds consistent opening hours across its Google Business Profiles and earns coverage in two city news sites. It gains local pack rankings and starts appearing in AI Mode answers to 'emergency dentist open Sunday near me'.
- An ecommerce brand discovers that a robots.txt rule blocks its category pages for all bots. Fixing it restores Googlebot crawling and also lets OAI-SearchBot and PerplexityBot reach pages that AI assistants had never cited before.
