SEO Glossary

AI crawlers are automated bots operated by AI platforms — including GPTBot (OpenAI), ClaudeBot (Anthropic), and PerplexityBot — that crawl the web to collect training data or answer live queries.

AI Overview is Google's AI-generated summary that appears at the top of certain search results pages, synthesising information from multiple sources into a direct answer before any organic links.

Alt text is the written description attached to an HTML image element. Search engines read it to understand image content; screen readers use it to describe images to visually impaired users.

AEO is the practice of structuring and presenting content so that AI-powered answer engines — including voice assistants, ChatGPT, and Perplexity — retrieve and cite it when responding to user queries.

A backlink is a hyperlink from one website pointing to a page on another website. Backlinks are one of the most influential ranking signals in Google's algorithm.

Breadcrumb navigation is a secondary navigation trail showing a user's location within a site hierarchy. Search engines use breadcrumbs to understand site structure and display them in search results.

An HTML element that tells search engines which version of a page is the preferred ("canonical") one to index.

A CDN is a geographically distributed network of servers that delivers static assets from a location close to each visitor, reducing load time and server strain.

Click depth is the number of clicks required to reach a page from the homepage. Pages deeper than 3–4 clicks are crawled less frequently and receive less internal link equity.

Google's set of user-experience metrics — LCP, INP and CLS — that measure loading, interactivity and visual stability.

The number of pages a search engine will crawl on your site within a given timeframe.

CLS measures how much visible page content unexpectedly shifts during loading. It is one of Google's three Core Web Vitals and directly affects page experience rankings.

Dynamic rendering serves a pre-rendered, crawler-friendly HTML version of a JavaScript-heavy page to search engine bots while serving the standard client-side version to human users.

Experience, Expertise, Authoritativeness and Trust — qualities Google uses to assess content quality.

Entity SEO is the practice of optimising a website so that search engines and AI systems recognise and correctly classify the real-world entities — people, organisations, products, places — that the site represents or covers.

GEO is the practice of optimising a website so that AI-powered answer engines — such as ChatGPT, Perplexity, and Google AI Overviews — can discover, read, understand, and cite its content.

Google Search Console is a free Google tool that reports on how Googlebot crawls, indexes, and ranks a website — including coverage errors, manual actions, and Core Web Vitals field data.

A Google ranking system that rewards people-first content and demotes content made primarily to rank.

hreflang is an HTML attribute that tells search engines which language and region a page is intended for, and links it to equivalent pages in other languages or regions.

HTTP status codes are three-digit numbers returned by a web server in response to a request. They tell crawlers and browsers whether the request succeeded, failed, or was redirected.

Index coverage ratio is the proportion of a site's crawled pages actually indexed by search engines. A low ratio often signals crawl waste, noindex misuse, or canonicalisation issues.

A Core Web Vital that measures how quickly a page visibly responds to user interactions; it replaced First Input Delay in 2024.

JavaScript rendering refers to page content built in the browser by JavaScript rather than delivered in the initial HTML. Search engine crawlers may not execute JavaScript, making this content invisible to them.

A Knowledge Panel is the information box that appears on the right side of Google search results displaying key facts about an entity — a brand, person, place, or organisation — pulled from Google's Knowledge Graph.

A Core Web Vital measuring how long the largest visible element takes to render. Aim for 2.5s or less.

llms.txt is a proposed standard file placed at a website's root to help AI language models understand the site's purpose, key pages, and authoritative content — the AI equivalent of sitemap.xml.

A meta description is the short HTML summary of a page's content. Google often displays it as the snippet under a search result title, directly influencing whether users click through.

Mobile-first indexing means Google primarily uses the mobile version of a page's content to determine rankings and indexing, reflecting that the majority of searches now happen on mobile devices.

Noindex is a directive that instructs search engine crawlers not to include a page in the search index. It can be set via an HTML meta tag or an HTTP response header.

Open Graph tags are HTML meta elements that control how a page's title, description, and image appear when shared on social platforms like Facebook, LinkedIn, and Slack.

A redirect automatically sends users and crawlers from one URL to another. The redirect type (301, 302, etc.) determines whether link equity is passed and how search engines treat the original URL.

robots.txt is a plain-text file at a website's root that instructs search engine crawlers which URLs they are allowed or not allowed to access. It controls crawl access but does not prevent indexing.

Search Generative Experience was the name Google used during the 2023–2024 testing phase for AI-generated summaries in search results. It was renamed AI Overviews (AIO) upon general rollout in May 2024.

Semantic SEO is the practice of optimising content for meaning and topical relevance rather than individual keyword frequency — helping search engines and AI systems understand what a page is about in full context.

A SERP is the page a search engine displays in response to a query. Modern SERPs contain organic results, paid ads, featured snippets, image packs, and AI-generated overviews, each competing for user attention.

Standardised markup (usually schema.org JSON-LD) that helps search engines understand a page and can unlock rich results.

The title tag is the HTML element that defines a page's title. It appears in the browser tab, as the clickable headline in search results, and as the default text when a page is bookmarked or shared.

URL structure refers to how a website organises its web addresses. Clean, descriptive, logically hierarchical URLs are easier for both search engines and users to understand and navigate.

An XML sitemap is a file that lists a website's important URLs and helps search engine crawlers discover and prioritise pages — especially those not easily found through internal links alone.

A zero-click search is a search query where the user's need is satisfied directly on the search results page — through a featured snippet, Knowledge Panel, calculator, or AI Overview — without clicking through to any website.