This is a free SEO course in 100 lessons, published one lesson a day and written by Txema Hermoso. It starts with what a search engine does with a page and ends with Google’s spam policies, parasite SEO and what you lose when you get caught. No signup, no email gate, no paid tier.

It is a curriculum rather than a blog: eight levels in a fixed order, each lesson readable on its own but sequenced so none depends on a concept you have not met yet.

What makes it different is hard to fake. Every factual claim carries a source, a date and a sample size where one exists. Claims practitioners disagree about are labelled contested instead of resolved for you. Where the evidence runs out, the lesson says so.

Who this course is for

Four kinds of reader, and the level order is built for all four.

  • Complete beginners who have never opened Google Search Console. Level 0 assumes nothing, including the vocabulary.
  • Writers and marketers told to “do SEO”, who want to know which of that advice has evidence behind it.
  • Working SEOs and SEO managers who need a defensible position on AI search for a meeting, with the studies attached.
  • Developers and technical leads who want to know which technical work moves rankings and which is folklore.

It is not for anyone who wants a certificate. No exam, no badge, no cohort. Just 100 lessons, all free.

What makes this course different

Every claim carries a source and a date, and that single rule disqualifies a large share of the SEO statistics currently in circulation.

One example runs through the whole curriculum. The claim that “AI traffic converts 4.4x better than organic” appears in dozens of agency decks and cannot be traced to any study with a disclosed methodology: every instance is a vendor blog citing another vendor blog. The only study with a real method (973 ecommerce sites, $20 billion combined revenue, August 2024 to July 2025, published 23 October 2025) found ChatGPT referrals converting worse than organic search, email and affiliate. This course teaches that claim as a worked example of statistic-laundering, not as a fact.

The rule also forces honesty about disagreement. Estimates of how many results carry an AI Overview run from 18% (Pew Research panel, March 2025) to 48% (BrightEdge, February 2026), because the measurement methods are not comparable. A course that hands you one number is hiding the method.

It means teaching the uncomfortable material too. Level 7 documents grey hat, black hat and parasite SEO and Google’s spam policies openly, because you cannot recognise an attack you have never seen described. Negative SEO, DMCA abuse and parasite pages on subdomains you own are done to you. Every lesson in that level states the penalty.

How the course works

One lesson is published per day, free, with no signup and no email gate. Nothing is drip-fed to an address, hidden behind a form or released by a purchase.

Every lesson has the same shape: what you will be able to do by the end, the evidence with dates, a table or set of thresholds, something you can execute (a checklist, a query, a decision tree), common mistakes with fixes, a short version that survives being quoted alone, an FAQ and a sources block.

Lessons get revised when the evidence changes, and the revision date stays visible. In a field where Reddit’s citation frequency in ChatGPT fell from roughly 60% to roughly 10% within weeks (Semrush, 230,000+ prompts, 14 July to 12 October 2025), an undated lesson is not trustworthy.

Publication order is the order of the listing below. As of 17 September 2026 only the first lesson is live, What SEO Actually Is in 2026. The remaining titles are fixed and listed in advance, so you can see what is coming.

The eight levels, and where to start

Start at the level matching what you can already do, not your job title.

Level Lessons Start here if
Level 0: SEO Fundamentals 12 You have never opened Search Console.
Level 1: On-Page SEO and Content 14 You write or commission content.
Level 2: Technical SEO 14 Pages not indexed, or a migration.
Level 3: Off-Page SEO and Link Building 12 Links, or an attack on your profile.
Level 4: GEO and AIO 14 You need evidence on AI search.
Level 5: Analytics and Measurement 10 You report SEO and must prove it.
Level 6: Advanced SEO Strategy 14 Local, ecommerce, international, programmatic.
Level 7: Grey Hat, Black Hat and Parasite SEO 10 Recognise manipulation, price the risk.

Complete beginner: start at Level 0, lesson 1, and read in order. Those 12 lessons are what every other level assumes you know: how crawling, indexing and ranking differ, what search intent does to everything downstream, and what a 2026 result page contains.

Working SEO or SEO manager: skim Levels 0 and 1 for the numbers and the sources, then jump. Level 2 if your problems are technical, Level 4 if they are AI search, Level 5 if the problem is reporting.

If you only care about being cited by ChatGPT: Level 4 is your level, but read Level 0 first, and here is the reason. 93.67% of AI Overview citations overlap with the top-10 organic results (Analyze, 56 million AI Overviews), so AI Overview visibility is mostly downstream of classic ranking. ChatGPT is the genuine exception, running its own index (“labrador”, with only 1.5% of its URLs in Bing’s top 20), yet even there the win condition is being read rather than retrieved: pages opened in thinking mode were cited 74% of the time against 7% for pages retrieved but never opened (Search Engine Land teardown, 17 August 2026, 1,200 answers). Crawlability, indexation and clean HTML are prerequisites on both surfaces. GEO without fundamentals is a tactic with nothing underneath it.

Why this course exists now

The click is disappearing faster than AI referrals are replacing it, and that asymmetry is the problem the whole course is built around.

68.01% of US Google searches ended without a click between January and April 2026 (Similarweb clickstream, published by SparkToro on 9 June 2026), up from 60.45% in 2024 and 49% in 2019. The measurement excludes Google’s mobile app, so it probably understates the real share.

Where an AI Overview appeared, users clicked a traditional result on 8% of visits against 15% of visits without one, a relative drop of about 47% (Pew Research behavioural panel: 900 US adults, 68,879 searches, 12,593 with an AI summary, March 2025, published 22 July 2025). Only 1% clicked a link inside the summary itself.

The traffic is not moving to the assistants either. In US clickstream data for manufacturing and industrial sites from January to July 2026, all AI channels combined accounted for 0.48% of sessions (Semrush), whose stated finding is that citations do not convert into visits at a predictable rate.

Side by side, those numbers annoy both camps. The loss is real and happening now, but it is a loss to zero-click behaviour on Google, not a migration of visitors to ChatGPT. The work is defending against click loss and being present where answers get assembled, not chasing a 0.48% referral channel. That is why 14 lessons go to GEO and AIO and 86 to everything else.

The full curriculum follows, in publication order. Lessons that are not published yet are listed as plain text; published lessons are links.

Level 0: SEO Fundamentals (12 lessons)

What SEO is, how search engines work, and the vocabulary every other level assumes you already have.

  1. What SEO Actually Is in 2026
  2. How Search Engines Work: Crawling, Indexing, Ranking
  3. Search Intent: The Four Types and Why Nothing Works Without It
  4. How Google Reads a Page: From HTML to Index
  5. SERP Anatomy 2026: What Actually Owns the First Screen
  6. Zero-Click Reality: What 68% of Searches Without a Click Means
  7. E-E-A-T Without the Mythology
  8. Quality Rater Guidelines: What They Actually Say
  9. Google Core Updates: What They Are, What They Aren’t, What To Do
  10. Keyword Research From Zero: The Complete Method
  11. Your First SEO Stack: The 6 Tools That Matter
  12. Your First SEO Audit in 90 Minutes

Level 1: On-Page SEO and Content (14 lessons)

Everything you control inside the page: content, structure, semantics and conversion.

  1. Title Tags: The Element Google Rewrites Most
  2. Meta Descriptions: What They Actually Do
  3. Heading Hierarchy: H1–H6 Without the Superstition
  4. Content Architecture: Silos, Clusters and Why They Matter
  5. Internal Linking: SEO’s Most Wasted Asset
  6. Writing for Humans and Models at the Same Time
  7. Keyword Cannibalization: Finding It and Fixing It
  8. Image Optimization: Alt, Format, Size and Core Web Vitals
  9. Semantic SEO: Entities, Not Keywords
  10. Structured Data That’s Actually Worth Doing
  11. Content Decay: Why Your Best Post Bleeds Traffic
  12. Content Audit and Pruning: What to Delete, What to Merge
  13. Formats That Get Cited: Tables, Definitions and First-Party Data
  14. CRO for SEOs: Traffic That Converts

Level 2: Technical SEO (14 lessons)

The infrastructure: crawling, rendering, indexing, speed and everything that breaks quietly.

  1. robots.txt in 2026: The Definitive Guide (AI Bots Included)
  2. XML Sitemaps: When They Matter and When They Don’t
  3. Crawl Budget: Who Actually Needs to Care
  4. Indexing: Why ‘Crawled — Currently Not Indexed’ Is a Quality Verdict
  5. Canonicals, noindex and the Art of Not Contradicting Yourself
  6. JavaScript SEO: Rendering, Hydration and What Googlebot Sees
  7. Core Web Vitals 2026: LCP, INP, CLS and What They’re Really Worth
  8. Redirects: 301, 302, Chains and Silent Losses
  9. HTTP Status Codes for SEOs
  10. Pagination, Facets and Ecommerce Crawl Hell
  11. Log File Analysis: The Most Underrated Instrument You Own
  12. Hreflang and Internationalization Without Breaking Things
  13. Site Migrations: The Checklist That Prevents Disaster
  14. Crawling Like a Professional with Screaming Frog

Level 3: Off-Page SEO and Link Building (12 lessons)

Authority, links, brand mentions and everything that happens outside your own domain.

  1. How Links Work in 2026 (And Why They’re No Longer Top 3)
  2. Backlink Profile Audits: What to Look At, In What Order
  3. Link Building That Survives a Spam Update
  4. Digital PR: The Only Link Tactic That Scales Clean
  5. Guest Posting: What’s Alive and What’s Link Spam
  6. Unlinked Brand Mentions: Why They Out-Correlate Backlinks
  7. Anchor Text: Natural Distribution and Manipulation Signals
  8. Toxic Links and Disavow: Why Almost Nobody Should Use It
  9. Negative SEO and Real Attacks: How to Defend
  10. DMCA Abuse as a Competitive Weapon
  11. Expired Domains: The Abuse, the Risk and Google’s Policy
  12. How to Tell If Your Link Building Is Working

Level 4: GEO and AIO: SEO for AI Search (14 lessons)

How AI Overviews, AI Mode, ChatGPT, Gemini and Perplexity choose what to cite, measured rather than guessed.

  1. GEO, AIO, AEO, LLMO: What They Mean and Which Ones Matter
  2. AI Overviews: How Citations Are Selected (The 93.67% That Explains It)
  3. AI Mode Is Not AI Overviews: 13.7% Overlap and What It Means
  4. How ChatGPT Search Really Works: The ‘Labrador’ Index Exposed
  5. Retrieved Isn’t Enough: Getting Read (74% vs 7%)
  6. The Absorption Pattern: Why Consensus Content Never Gets Cited
  7. The GEO Paper: +41% for Quotations, +40% for Statistics
  8. Writing Retrievable Chunks: Optimizing at Passage Level
  9. Entities and Disambiguation: How a Model Recognizes You
  10. Does Schema Help AI Citations? The Evidence Says No
  11. llms.txt: Autopsy of a Standard Nobody Reads (97%)
  12. AI Crawlers: GPTBot, ClaudeBot, PerplexityBot and the Cost of Blocking
  13. Cloudflare, Pay-Per-Crawl and the Economics of Content
  14. Reddit, YouTube and LinkedIn: The 59% of Citations You Don’t Control

Level 5: Analytics and Measurement (10 lessons)

Measure what exists, admit what cannot be measured, and stop lying to yourself with your own data.

  1. Search Console In Depth: What It Tells You and What It Hides
  2. GSC’s Generative AI Report: Impressions Only
  3. Measuring LLM Visibility (And Every Tool’s Limits)
  4. GA4 for SEOs: The Reports You Actually Use
  5. Attributing AI Traffic: ChatGPT, Perplexity and Gemini in Your Data
  6. Reading a Traffic Drop Without Panicking
  7. SEO Statistics That Are Lies (And How to Spot Them)
  8. SEO Forecasting: Honest Models, Not Promises
  9. SEO Dashboards: What to Include and What to Cut
  10. SEO Testing: Running an Experiment That Means Something

Level 6: Advanced SEO Strategy (14 lessons)

Local, ecommerce, international and programmatic SEO, penalty recovery and portfolio decisions.

  1. Local SEO: From Business Profile to Neighbourhood Map
  2. Ecommerce SEO: Catalogue, Facets and Cannibalization
  3. International SEO: Domain Structure and Market Choice
  4. Programmatic SEO: Scaling Without Triggering Scaled Content Abuse
  5. Using AI for Content Without Getting Penalized
  6. Recovering From a Core Update: The Real Protocol
  7. Manual Actions and Reconsideration: How You Get Out
  8. Building Topical Authority That Actually Compounds
  9. Competitive Analysis: Reverse-Engineering Who Beats You
  10. Domain Portfolios: When One More Site Makes Sense
  11. YouTube and Video SEO: Where 59% of AI Citations Start
  12. Brand as an SEO Channel: Why Branded Search Changes Everything
  13. SEO in a World of Agents: WebMCP and Agentic Search
  14. Selling SEO Upward: Getting Budget From Leadership

Level 7: Grey Hat, Black Hat and Parasite SEO (10 lessons)

What it is, how it gets detected and what happens to the people who do it. Documented so you can defend yourself, not copy it.

  1. Black Hat, Grey Hat, White Hat: Where the Line Actually Is
  2. Google’s 18 Spam Policies, Explained One by One
  3. Parasite SEO: How It Works and Why Google Hunts It
  4. Site Reputation Policy: The August 2026 European Carve-Out
  5. PBNs and Link Networks: Anatomy of a Detection
  6. Cloaking, Doorways and Sneaky Redirects
  7. Scaled Content Abuse: The Line Between Scaling and Spamming
  8. Back Button Hijacking: The 2026 Spam Policy
  9. Spotting Black Hat in Your Competition (And Whether to Report It)
  10. The Real Risk Calculation: What You Lose When You’re Caught

About the author

Every lesson on doctor-seo.net is written by Txema Hermoso. There is no editorial team and no rotating byline, which matters because it makes the sourcing checkable: one person is accountable for every number on the site. His background is on his LinkedIn profile.

Corrections are the most useful message you can send. If a lesson cites something you can show is wrong, out of date or traceable only to a vendor blog, it gets fixed with a visible revision date.

Frequently asked questions

Is it really free?

Yes. All 100 lessons are free: no signup, no email capture, no paywall, no upsell. There is no paid version. The course doubles as a demonstration of the method it teaches, the closest thing to a commercial motive here.

Do I need technical knowledge?

Not for Levels 0, 1, 3, 6 and 7. Level 2 (technical SEO) and Level 5 (analytics) expect you to read HTTP status codes, run a crawler such as Screaming Frog and work in a spreadsheet. No lesson requires code, though the JavaScript SEO and log analysis lessons land better if you have seen a server log.

How long does it take?

At one lesson a day, a little over 14 weeks. Reading a lesson takes 10 to 20 minutes; running its checklist or crawl takes longer, and that is where the value sits. If you already work in SEO you can read a whole level in an afternoon.

Is this current, given how fast AI search changes?

Every statistic carries its date, so you can see how old a number is instead of guessing. That is the only honest answer in a field where Reddit’s ChatGPT citation frequency fell from roughly 60% to roughly 10% in weeks and Cloudflare flipped its default crawler rules on 15 September 2026. Lessons with short-shelf-life numbers say so, and structural facts about crawling, intent and links change far more slowly.

Why does it teach black hat SEO?

Because you cannot defend against a technique you have never seen described, and because several of them are done to you. Negative SEO, DMCA takedown abuse, parasite pages on domains you own and competitors ranking through link networks are defensive topics first. Google’s 18 spam policies are the actual rulebook, and almost nobody has read all of them. Level 7 documents each technique, how detection works and what is lost when it fails.

Sources

  • SparkToro / Similarweb clickstream, 9 June 2026: 68.01% zero-click, US, Jan–Apr 2026.
  • Pew Research Center behavioural panel, March 2025, published 22 July 2025: 900 US adults, 68,879 searches; 8% versus 15% click rate with and without an AI summary.
  • Semrush / PPC Land, US clickstream, Jan–Jul 2026: AI channels 0.48% of sessions; citations do not convert into visits predictably.
  • Semrush, most-cited domains, 230,000+ prompts, 14 Jul–12 Oct 2025: Reddit’s ChatGPT citation collapse.
  • Analyze, 56 million AI Overviews: 93.67% of AIO citations overlap the top-10 organic results.
  • Search Engine Land, ChatGPT retrieval teardown, 17 August 2026, 1,200 answers: the “labrador” index; 74% versus 7% citation rate.
  • Pew Research Center, March 2025 (18%) and BrightEdge, February 2026 (48%): divergent AIO coverage estimates.
  • SSRN, “ChatGPT Referrals to E-Commerce Websites”, 973 sites, published 23 October 2025.