SEO Encyclopedia: A to Z of SEO Terms and Techniques

This encyclopedia explains 404 SEO terms and techniques in plain English. Each entry covers what the term means, why it matters, how to put it into practice and the mistakes to avoid, with links to related entries so you can follow a topic as deep as you like. Bookmark this page and come back whenever you need to understand a new term or fix something on your own website.

New to SEO? Start Here

1. Read what SEO is for a short introduction.
2. Learn how search engines work: crawling, indexing and ranking.
3. Understand the main Google ranking factors and the importance of search intent.
4. Follow how to get your website on Google and how to get on Google’s first page.
5. Check your site with the free Google Search Console, then work through an SEO audit.

Browse by Topic

• SEO Fundamentals (42 entries)
• Google Algorithms & Updates (24 entries)
• Technical SEO (80 entries)
• On-Page SEO (39 entries)
• Content & Keywords (45 entries)
• Links & Off-Page SEO (36 entries)
• Local SEO (24 entries)
• Ecommerce & International SEO (18 entries)
• Platform & CMS SEO (9 entries)
• Video, Image & Discover SEO (9 entries)
• AI Search, AEO & GEO (47 entries)
• Measurement & Tools (31 entries)

SEO Fundamentals

Start here if you are new to SEO: how search engines work, what decides rankings and how to plan your approach.

• How Search Engines Work: how Google crawls, indexes and ranks pages.
• SERP (Search Engine Results Page): the search results page and its features.
• Organic Traffic: unpaid visitors from search engines.
• Google Ranking Factors: the signals Google uses to order results.
• Google Algorithm Updates: core, spam and other ranking changes.
• Google Penalties: manual actions and algorithmic demotions.
• White Hat SEO: ethical SEO that follows Google’s guidelines.
• Black Hat SEO: manipulative tactics and their risks.
• SEO vs PPC: organic search compared with paid ads.
• SEO Strategy: planning SEO around business goals.
• Branded Search: searches for your business by name.
• Zero-Click Searches: searches that end without a click.
• Search Engine: software that finds, stores and ranks web content.
• Googlebot: the web crawler Google uses to fetch pages.
• Search Query: the words someone types or speaks into search.
• Keywords: the words and phrases pages aim to rank for.
• Organic vs Paid Results: how unpaid listings differ from search ads.
• Grey Hat SEO: tactics between Google-approved methods and outright spam.
• Negative SEO: deliberate attempts to harm a competitor's search rankings.
• Search Quality Rater Guidelines: the handbook Google gives its human search raters.
• YMYL (Your Money or Your Life): topics that can affect health, money or safety.
• Google Spam Policies: the rules Google uses to define search spam.
• Manual Actions: penalties applied by Google's human reviewers.
• Google Sandbox: the theory that new sites are held back.
• Cloaking: showing search engines different content from users.
• Keyword Stuffing: overloading pages with keywords to manipulate rankings.
• Doorway Pages: near-identical pages built to capture similar searches.
• Hidden Text and Links: content concealed from users but shown to crawlers.
• Scraped Content: content copied from other sites without adding value.
• Site Reputation Abuse: third-party content exploiting a host site's rankings.
• Scaled Content Abuse: mass-producing low-value pages to manipulate rankings.
• Expired Domain Abuse: using an old domain's reputation to boost weak content.
• Parasite SEO: ranking third-party content on someone else's strong domain.
• Programmatic SEO: creating many targeted pages from templates and data.
• Enterprise SEO: SEO for very large websites and organisations.
• SEO ROI: measuring the financial return from SEO investment.
• Bing SEO: optimising your site to rank in Microsoft Bing.
• Search Personalisation: how results change for each individual searcher.
• Query Deserves Freshness (QDF): why some searches favour recent content.
• Dwell Time: how long a searcher stays before returning to results.
• Pogo-Sticking: bouncing between search results to find an answer.
• User Signals: how searcher behaviour may influence rankings.

Google Algorithms & Updates

The named Google systems and updates that shaped modern SEO, from Panda and Penguin to the helpful content and core updates.

• Google Panda: Google's 2011 update targeting low-quality content.
• Google Penguin: Google's 2012 update against manipulative link building.
• Google Hummingbird: Google's 2013 rebuild for understanding query meaning.
• RankBrain: Google's machine learning system for interpreting queries.
• BERT: Google's language model for understanding words in context.
• MUM (Multitask Unified Model): Google's multimodal, multilingual AI model for complex searches.
• Neural Matching: Google's AI system linking queries to underlying concepts.
• Passage Ranking: how Google ranks pages using specific relevant passages.
• Helpful Content Update: Google's 2022 system targeting content made for search engines.
• Google Core Updates: broad changes to Google's main ranking systems.
• Reviews System (Product Reviews Update): how Google rewards genuinely useful, first-hand reviews.
• Medic Update: the August 2018 core update that shook health sites.
• Mobilegeddon: google's 2015 update boosting mobile-friendly pages.
• Page Experience Update: the 2021 update adding Core Web Vitals to rankings.
• Link Spam Update: updates that neutralise manipulative and paid links.
• SpamBrain: google's machine learning system for detecting search spam.
• Florida Update: the 2003 update that ended easy keyword-stuffed rankings.
• Pigeon Update: the 2014 update that reshaped local search results.
• Possum Update: the 2016 local update that filtered similar nearby listings.
• Freshness Update: the 2011 update favouring recent content for timely searches.
• Caffeine Update: the 2010 rebuild of Google's web indexing system.
• Exact Match Domain (EMD) Update: the 2012 update targeting low-quality keyword domain names.
• NavBoost: the Google system that uses click data to refine rankings.
• Google Search Documents Leak (2024): leaked internal Google API docs revealing ranking-related attributes.

Technical SEO

How search engines crawl, render and index your website, and how to keep it fast, secure and error-free.

• Technical SEO: making sites crawlable, indexable and fast.
• Crawling: how search engines discover pages.
• Indexing: how pages get into Google’s index.
• Rendering: how Google runs JavaScript to see content.
• Robots.txt: controlling which pages bots can crawl.
• XML Sitemap: listing the URLs you want indexed.
• Canonical Tag: choosing the main version of a page.
• Noindex Tag: keeping pages out of search results.
• Duplicate Content: the same content at several URLs.
• HTTP Status Codes: 200, 301, 404, 500 and what they mean.
• 301 Redirect: permanently moving a URL without losing value.
• 404 Error: missing pages and when to fix them.
• Redirect Chains: multiple redirects and loops.
• HTTPS and SSL: secure connections and certificates.
• Core Web Vitals: Google’s loading, responsiveness and stability metrics.
• Largest Contentful Paint (LCP): how fast the main content appears.
• Cumulative Layout Shift (CLS): how much the page jumps while loading.
• Interaction to Next Paint (INP): how quickly the page responds to input.
• Page Speed: making pages load and respond faster.
• Mobile-First Indexing: Google ranking your mobile pages.
• Schema Markup: structured data that labels your content.
• Hreflang: targeting languages and countries.
• JavaScript SEO: keeping JavaScript sites indexable.
• Crawl Budget: how much Google crawls on large sites.
• Log File Analysis: what server logs reveal about bots.
• Site Architecture: organising pages and links.
• Orphan Pages: pages with no internal links.
• Pagination: splitting lists across several pages.
• Faceted Navigation: filters and the URLs they create.
• Website Migration: changing domain or platform safely.
• Web Crawler: software that automatically discovers and fetches web pages.
• User-Agent: the string identifying which browser or bot requests a page.
• Crawl Errors: problems stopping search engines from fetching your pages.
• Click Depth: how many clicks a page sits from the homepage.
• Time to First Byte (TTFB): how quickly a server starts sending a page.
• First Contentful Paint (FCP): when the first piece of content appears on screen.
• Total Blocking Time (TBT): how long scripts stop a page responding to input.
• Render-Blocking Resources: files that stop a page displaying until loaded.
• Lazy Loading: delaying offscreen images and media until needed.
• Image Compression and WebP: shrinking image files with smarter formats and settings.
• Content Delivery Network (CDN): servers worldwide that deliver your site faster.
• Browser Caching: storing site files locally for faster repeat visits.
• Minification: stripping unneeded characters from code to shrink files.
• Gzip and Brotli Compression: squeezing text files smaller as they travel.
• HTTP/2 and HTTP/3: newer web protocols that load pages more efficiently.
• 302 Redirect: a temporary redirect to another URL.
• 410 Gone: a status code saying a page was permanently removed.
• Soft 404: an empty or missing page that returns success.
• 5xx Server Errors: status codes showing the server failed a request.
• Redirect Loops: redirects that point back to themselves endlessly.
• Meta Refresh: an HTML tag that reloads or redirects a page.
• Meta Robots Tag: page-level instructions for indexing and snippets.
• X-Robots-Tag: robots directives sent in the HTTP header.
• Index Bloat: too many low-value pages in Google's index.
• URL Parameters: query strings that change or track page content.
• Trailing Slashes: the slash at the end of a URL.
• WWW vs Non-WWW: choosing one hostname version for your website.
• Self-Referencing Canonical: a canonical tag that points to its own page.
• Cross-Domain Canonical: a canonical tag pointing to another website's URL.
• IndexNow: a protocol for instantly notifying search engines of changes.
• Google Indexing API: Google's API for job posting and livestream pages.
• Sitemap Index: a file that lists multiple XML sitemaps.
• Image Sitemap: a sitemap that helps search engines find images.
• Video Sitemap: a sitemap that describes videos hosted on your pages.
• News Sitemap: a sitemap listing recent articles for Google News.
• HTML Sitemap: a web page linking to a site's main pages.
• JSON-LD: the recommended format for adding structured data.
• Server-Side Rendering (SSR): building full page HTML on the server.
• Client-Side Rendering (CSR): building page content in the browser with JavaScript.
• Dynamic Rendering: serving pre-rendered HTML to bots, JavaScript to users.
• Single Page Application (SPA) SEO: making JavaScript single page apps crawlable and indexable.
• Infinite Scroll: loading more content automatically as users scroll.
• AMP (Accelerated Mobile Pages): a stripped-down HTML framework for fast mobile pages.
• Responsive Design: one site that adapts its layout to any screen.
• Intrusive Interstitials: pop-ups that block content, especially on mobile.
• Accessibility and SEO: how accessible websites overlap with good SEO.
• Hacked Site Recovery: cleaning a compromised website and regaining search trust.
• Subdomain vs Subfolder: choosing between blog.example.com and example.com/blog.
• HTTPS Migration: moving a website from HTTP to secure HTTPS.
• Staging Sites: private test copies of a website used before launch.

On-Page SEO

How to optimise individual pages, from titles and headings to images and internal links.

• On-Page SEO: optimising individual pages.
• Search Intent: the goal behind a search.
• Title Tag: your headline in search results.
• Meta Description: the snippet that earns the click.
• Header Tags (H1-H6): structuring pages with H1 to H6.
• URL Structure: clean, readable web addresses.
• Image SEO: fast, well-described images.
• Alt Text: describing images for people and search engines.
• Internal Linking: linking your own pages together.
• Anchor Text: the clickable words of a link.
• Keyword Cannibalisation: your pages competing with each other.
• Featured Snippets: answer boxes at the top of results.
• Breadcrumbs: showing where a page sits in your site.
• Open Graph Tags: controlling social sharing previews.
• Rich Results: listings with stars, prices and extras.
• Keyword Placement: where to use target keywords on a page.
• Keyword Density: how often a keyword appears relative to total words.
• LSI Keywords: a popular myth about related terms and rankings.
• Content Length: how long a page's content should be.
• Above the Fold: the part of a page visible without scrolling.
• Title Tag Rewrites: when Google changes your page title in results.
• Meta Keywords Tag: an obsolete HTML tag ignored by Google.
• Readability: how easy page content is to read and understand.
• Content Freshness: how up to date content is, and why it matters.
• Outbound Links: links from your pages to other websites.
• Table of Contents: a linked list of a page's sections.
• FAQ Sections: on-page lists of common questions and answers.
• Image File Names: descriptive names for image files before upload.
• Twitter (X) Cards: meta tags controlling link previews on X.
• Favicon: the small site icon shown in tabs and results.
• Sitelinks: extra page links shown beneath a search result.
• Search Snippet: the title, URL and description shown in results.
• Review Snippets: star ratings shown in search results via markup.
• Author Bylines and Author Pages: showing who wrote content and why they're credible.
• About Page SEO: optimising the page that explains who runs a site.
• Homepage SEO: optimising a site's main page for search and users.
• Landing Page SEO: optimising pages built to rank and convert visitors.
• Blog SEO: optimising blog posts so they earn organic traffic.
• Published and Updated Dates: how pages show when content was published or changed.

Content & Keywords

How to research keywords and create content that deserves to rank.

• Keyword Research: finding what your customers search for.
• Search Volume: how often a keyword is searched.
• Keyword Difficulty: how hard a keyword is to rank for.
• Long-Tail Keywords: specific, lower-volume searches.
• Keyword Clustering: grouping keywords for one page.
• Semantic SEO: optimising for meaning and topics.
• Entities: people, places, brands and concepts Google recognises.
• Topical Authority: depth and trust on a subject.
• Topic Clusters: pillar pages and supporting content.
• SEO Copywriting: writing content that ranks and converts.
• Thin Content: pages with little real value.
• Content Decay: pages slowly losing traffic.
• Content Pruning: improving, merging or removing weak pages.
• E-E-A-T: experience, expertise, authoritativeness and trust.
• Helpful Content: people-first content Google rewards.
• People Also Ask: expandable related questions in results.
• Informational Keywords: searches made to learn something or answer a question.
• Commercial Keywords: searches made while researching a purchase.
• Transactional Keywords: searches made by people ready to buy or act.
• Navigational Keywords: searches for a specific brand, website or page.
• Seed Keywords: the starting words that keyword research grows from.
• Head Terms: short, broad keywords with high search volume.
• Question Keywords: searches phrased as questions, such as how or why.
• Zero-Volume Keywords: keywords tools report as having no searches.
• Keyword Gap Analysis: finding keywords competitors rank for that you miss.
• SEO Competitor Analysis: studying rival sites to shape your SEO plan.
• Content Gap: topics your audience wants that your site lacks.
• Keyword Mapping: assigning target keywords to specific pages on a site.
• Search Seasonality: predictable rises and falls in search demand.
• Content Strategy: the plan for what content to create and why.
• Content Calendar: a schedule for planning and publishing content.
• Pillar Page: a broad hub page anchoring a topic cluster.
• Evergreen Content: content that stays relevant and useful for years.
• Content Refresh: updating existing pages to improve accuracy and rankings.
• Content Brief: a set of instructions guiding a writer's page.
• AI-Generated Content: text or media produced with AI writing tools.
• Original Research: new data or findings you gather and publish yourself.
• Information Gain: how much new information a page adds.
• Comparison Pages: pages weighing up products, services or options side by side.
• Listicles: articles structured as a numbered or bulleted list.
• How-To Content: step-by-step guides that help readers complete a task.
• Glossary Pages: pages that define the key terms of a subject.
• User-Generated Content: content created by customers or users, not the site.
• Content Syndication: republishing your content on other websites.
• Content Repurposing: turning existing content into new formats.

Links & Off-Page SEO

How other websites build your authority through links, mentions and reputation.

• Off-Page SEO: links, mentions and reputation.
• Backlinks: links from other websites to yours.
• Link Building: earning links the right way.
• Referring Domains: unique websites linking to you.
• Nofollow, Sponsored and UGC Links: nofollow, sponsored and UGC links.
• Domain Authority: third-party authority scores explained.
• PageRank: Google’s original link algorithm.
• Link Equity: the value a link passes.
• Toxic Backlinks: harmful links and when they matter.
• Disavow Tool: asking Google to ignore bad links.
• Digital PR: earning media coverage and links.
• Broken Link Building: replacing dead links with your content.
• Unlinked Brand Mentions: turning mentions into links.
• Dofollow Links: standard links that can pass ranking value.
• Link Velocity: how quickly a site gains or loses backlinks.
• Link Profile: the overall mix of links pointing to a site.
• Guest Posting: writing articles for other websites to reach their audience.
• Niche Edits: links inserted into existing articles on other sites.
• Private Blog Networks (PBNs): networks of sites built only to pass links.
• Link Schemes: manipulative linking practices that break Google's spam policies.
• Paid Links: links bought in exchange for money or goods.
• Reciprocal Links: two sites linking to each other.
• Skyscraper Technique: improving popular content, then pitching it for links.
• Journalist Requests (HARO-Style Link Building): answering reporters' source requests to earn press links.
• Linkable Assets: content created specifically to attract links naturally.
• Resource Page Link Building: earning links from curated lists of useful resources.
• Trust Flow and Citation Flow: Majestic's scores for link quality and link volume.
• Domain Rating (DR): Ahrefs' score for the strength of a site's backlinks.
• Spam Score: Moz's estimate of how spam-like a site appears.
• Link Reclamation: recovering backlinks that were lost, broken or missing.
• Backlink Analysis: reviewing the links pointing to a website.
• Co-Citation and Co-Occurrence: how being mentioned alongside others builds topical associations.
• Social Signals: likes, shares and comments on social media.
• Press Releases and SEO: how news announcements can, and cannot, help search visibility.
• Directory Submissions: listing a website in online business directories.
• Sitewide and Footer Links: links repeated across every page of a website.

Local SEO

How to get found by customers in your area through Google Maps and local results.

• Local SEO: getting found by nearby customers.
• Google Business Profile: your listing in Google Maps and Search.
• Map Pack: the three local results with a map.
• NAP Consistency: keeping name, address and phone identical.
• Local Citations: business listings across the web.
• Online Reviews: reviews, ratings and local rankings.
• Local Landing Pages: pages for each town or area you serve.
• Service Area Business: businesses that travel to customers.
• Local Ranking Factors: what decides who ranks in local search results.
• Google Maps SEO: getting a business found inside Google Maps.
• Google Business Profile Categories: labels that tell Google what a business is.
• Google Business Profile Posts: short updates published directly on a business profile.
• Review Management: getting, monitoring and responding to customer reviews.
• Fake Reviews: reviews that do not reflect genuine customer experiences.
• LocalBusiness Schema: structured data describing a physical business.
• Apple Business Connect: Apple's free tool for managing Apple Maps listings.
• Bing Places: Microsoft's free business listing service for Bing.
• Near Me Searches: local queries that rely on the searcher's location.
• Multi-Location SEO: local SEO for businesses with several branches.
• Local Link Building: earning links from websites in your area.
• Local Services Ads: Google's pay-per-lead ads for local service providers.
• Geo-Grid Rank Tracking: measuring local rankings across a map grid.
• Hyperlocal SEO: targeting neighbourhoods, streets and landmarks, not just cities.
• Google Business Profile Suspension: when Google restricts or removes a business profile.

Ecommerce & International SEO

SEO for online shops and for businesses targeting several countries.

• Ecommerce SEO: SEO for online shops.
• Product Page SEO: optimising individual products.
• Category Page SEO: optimising category and collection pages.
• International SEO: targeting several countries and languages.
• Product Schema: structured data that describes products, prices and stock.
• Product Variants: handling sizes, colours and options of one product.
• Out-of-Stock Products: handling product pages that cannot currently be bought.
• Product Descriptions: the text that sells and explains each product.
• Ecommerce Site Structure: how an online shop organises categories and products.
• Google Merchant Center and Free Listings: the tool for showing products across Google for free.
• Amazon SEO: optimising product listings to rank in Amazon search.
• Geotargeting: signalling which countries a website or page serves.
• ccTLD (Country Code Top-Level Domain): a domain ending tied to one country.
• x-default Hreflang: the fallback page for unmatched languages and regions.
• International Site Structure: how a website organises versions for different countries.
• Localisation vs Translation: adapting content for a market, not just its language.
• Multilingual SEO: optimising a website to rank in several languages.
• International Keyword Research: finding what people search for in each market.

Platform & CMS SEO

How SEO works on the most common website platforms and content management systems.

• WordPress SEO: optimising a WordPress website for search engines.
• Shopify SEO: optimising a Shopify store to rank in search.
• Wix SEO: optimising a Wix website for search engines.
• Squarespace SEO: optimising a Squarespace website to rank in search.
• Webflow SEO: optimising a Webflow website for search engines.
• WooCommerce SEO: optimising WordPress online shops built on WooCommerce.
• Magento (Adobe Commerce) SEO: optimising large shops built on Magento or Adobe Commerce.
• Headless CMS SEO: SEO for sites with separate content and front-end systems.
• SEO Plugins: add-ons that bring SEO controls to a CMS.

Video, Image & Discover SEO

Getting visibility beyond the ten blue links: video, images, Google Discover and news.

• Video SEO: helping videos get found in search results.
• YouTube SEO: getting videos found in YouTube and Google search.
• Video Schema: structured data that describes videos to search engines.
• Google Images SEO: getting images found and clicked in Google Images.
• Google Discover: Google's personalised content feed, shown without a search.
• Google News SEO: optimising news content for Google News and news features.
• Visual Search and Google Lens: searching with images and cameras instead of words.
• Podcast SEO: helping podcasts and episodes get found in search.
• Top Stories: Google's news carousel for timely, newsworthy searches.

AI Search, AEO & GEO

How to stay visible as people search with AI Overviews, AI Mode, ChatGPT, Perplexity and other assistants: answer engine optimisation (AEO), generative engine optimisation (GEO) and how AI systems find and cite content.

• AI SEO: visibility in AI-powered search.
• Generative Engine Optimisation (GEO): getting cited in AI-generated answers.
• AI Overviews: Google’s AI summaries in search results.
• Google AI Mode: Google’s conversational AI search.
• Answer Engine Optimisation (AEO): being chosen as the direct answer.
• ChatGPT Search: how ChatGPT finds and cites websites.
• llms.txt: a proposed file for AI tools.
• Large Language Models (LLMs): AI systems that generate text by predicting language.
• Retrieval-Augmented Generation (RAG): AI answers built from freshly retrieved source documents.
• AI Citations: source links that AI answers credit for their information.
• AI Visibility: how often a brand appears in AI-generated answers.
• AI Share of Voice: your share of brand mentions in AI answers.
• LLM Optimisation (LLMO): making your content easy for AI models to use.
• AI Crawlers: bots that fetch web pages for AI companies.
• GPTBot: the crawler OpenAI uses to collect training data.
• Google-Extended: the robots.txt token controlling Gemini's use of content.
• Robots.txt for AI Bots: using robots.txt rules to allow or block AI crawlers.
• Perplexity SEO: getting your pages cited in Perplexity's AI answers.
• Microsoft Copilot SEO: getting your content cited in Microsoft Copilot answers.
• Google Gemini and Search: how Google's Gemini AI models shape search results.
• Claude and AI Assistants: how Claude and similar assistants find and cite websites.
• Query Fan-Out: how AI search splits one question into many searches.
• Grounding: tying AI answers to real, verifiable sources.
• AI Hallucinations: when AI tools state false information as fact.
• Embeddings: number lists that capture the meaning of text.
• Vector Search: finding results by meaning using numerical vectors.
• Semantic Search: search that understands meaning and intent, not just words.
• Conversational Search: searching through natural back-and-forth dialogue with follow-ups.
• Voice Search: searching by speaking to a phone or smart speaker.
• Answer Boxes and Direct Answers: search features that answer questions directly on results pages.
• Knowledge Graph: the database of entities and links behind Google results.
• Knowledge Panel: the information box about an entity in Google.
• Brand Entity: how search engines recognise your brand as a thing.
• Wikidata and Wikipedia for SEO: how open knowledge bases shape entity understanding.
• FAQ Schema: structured data that marks up questions and answers.
• HowTo Schema: structured data that marks up step-by-step instructions.
• Speakable Schema: markup that flags text suited to being read aloud.
• Content Chunking for AI: structuring pages into self-contained, extractable sections.
• Citation-Worthy Content: content that AI tools and writers choose to cite.
• AI Overview Optimisation: improving your chances of appearing in Google AI Overviews.
• AI Referral Traffic: visits that arrive from AI chatbots and assistants.
• Prompt Tracking: monitoring how AI tools answer prompts about your market.
• AI Agents and Agentic Search: AI that searches and completes tasks on your behalf.
• Search Generative Experience (SGE): Google's experiment that became AI Overviews.
• Multimodal Search: searching with images, voice and video, not just text.
• Reddit and Forums in AI Answers: why community discussions appear so often in AI answers.
• AI Content Licensing: agreements that let AI companies use publishers' content.

Measurement & Tools

How to measure, audit and report on SEO performance.

• Google Search Console: Google’s free performance and indexing tool.
• Google Analytics 4: tracking what organic visitors do.
• SEO Audit: a full health check of your website.
• SEO KPIs: the metrics that show SEO is working.
• Click-Through Rate (CTR): the share of impressions that become clicks.
• Impressions: how often your pages appear in results.
• Rank Tracking: monitoring keyword positions.
• SEO Reporting: explaining SEO results clearly.
• SEO Tools: the software that supports SEO work.
• Ahrefs: an SEO platform known for backlink and keyword data.
• Semrush: an all-in-one platform for SEO and online marketing.
• Moz: the SEO software company behind Domain Authority.
• Screaming Frog: a desktop crawler for technical SEO audits.
• Google Trends: free tool showing how search interest changes over time.
• Google Keyword Planner: free Google Ads tool for keyword ideas and volumes.
• Bing Webmaster Tools: free Microsoft console for monitoring sites in Bing.
• PageSpeed Insights: free Google tool for testing speed and Core Web Vitals.
• Lighthouse: open-source tool that audits page quality and speed.
• Chrome UX Report (CrUX): public dataset of real Chrome users' page experience.
• Looker Studio: free Google tool for building data dashboards.
• Google Tag Manager: free tool for managing tracking codes without editing code.
• Engagement Rate and Bounce Rate: how GA4 measures whether visitors actually engage.
• Conversion Tracking: measuring the valuable actions visitors take on your site.
• Attribution: how credit for a conversion is shared between channels.
• UTM Parameters: tags added to links to track campaign traffic.
• Average Position: your mean Google ranking across all search impressions.
• Search Visibility: how prominently a site appears across tracked searches.
• URL Inspection Tool: shows how Google crawls and indexes a single page.
• Rich Results Test: free Google tool for checking rich result eligibility.
• SEO Crawlers: tools that crawl your site to find technical issues.
• SEO Forecasting: estimating future organic traffic and results.

More SEO Guides

• Top 10 SEO myths busted
• Why Google rankings drop
• Discovered, currently not indexed: how to fix it
• How to fix a CLS issue on mobile
• How to rank in ChatGPT with AI SEO
• How to become an SEO expert

How to Use This Encyclopedia

Each entry starts with a short definition, so you can get the answer quickly, then goes deeper with practical steps, common mistakes and key takeaways. The Related Terms list at the end of every entry links to the concepts that connect to it. If you are working on a specific problem, start with the entry that names it and follow the links from there. The encyclopedia is updated as search changes, including new AI search features.

Need Hands-On Help?

Learning SEO yourself is worthwhile, but some problems need experience to diagnose quickly. I am Paul Hoda, an independent SEO consultant in London, and I have worked on search since 2005. If you would like a second opinion on your website, get a free SEO check, read what an SEO consultant does, or see how much an SEO consultant costs.