SEO glossary

The terms that come up in an SEO audit, defined in plain English. Thirty entries, no jargon used to explain other jargon.

Alt text

A short text description of an image, held in the alt attribute. Read aloud by screen readers and used by search engines to understand image content.

Answer engine

A tool that responds to a question directly rather than returning a list of links, such as ChatGPT, Perplexity or Google's AI Overviews.

Canonical link

A tag naming the preferred address for a page, used to consolidate ranking signals when the same content is reachable at several addresses.

Core Web Vitals

Google's measures of loading, interactivity and visual stability: Largest Contentful Paint, Interaction to Next Paint, and Cumulative Layout Shift.

Crawl budget

The number of pages a search engine will fetch from a site in a given period. Relevant mainly to large sites.

Crawler

Software that fetches pages automatically to index them. Also called a bot or spider. Googlebot and Bingbot are the best known.

Cumulative Layout Shift

A Core Web Vital measuring how much page content moves around while loading. Commonly caused by images without declared dimensions.

Duplicate content

The same or near-identical content available at more than one address. It splits ranking signals rather than incurring a penalty in most cases.

Featured snippet

An answer extracted from a page and shown at the top of search results, above the ordinary listings.

H1

The top-level heading on a page, stating what the page is about. A page should normally have exactly one.

HTTPS

HTTP carried over an encrypted TLS connection. Required for the browser padlock and a lightweight ranking signal.

Indexing

The process of storing a fetched page so it can be returned in results. A page can be crawled without being indexed.

JSON-LD

The recommended format for structured data: a block of JSON in a script tag describing the page using schema.org vocabulary.

llms.txt

An emerging convention: a plain-text file at the root of a site summarising it for AI assistants and pointing at the pages worth reading.

Local pack

The block of three map listings shown for searches with local intent. Driven largely by Google Business Profile rather than the website itself.

Meta description

A short summary in the head of a document, often used as the snippet text in search results. Not a direct ranking factor.

Mobile-first indexing

Google's practice of using the mobile version of a page for indexing and ranking, regardless of the device a searcher is using.

NAP

Name, address and phone number. Consistency across your site and third-party listings supports local ranking.

Noindex

A directive telling search engines not to include a page in results. Must be readable by the crawler, so the page cannot also be blocked in robots.txt.

Open Graph

Meta tags controlling how a link appears when shared on social platforms and in messaging apps.

Organic results

Listings earned through relevance rather than paid for. Distinct from the advertisements above and beside them.

Rich result

A search listing enhanced with extra detail such as ratings, prices or opening hours, made possible by structured data.

robots.txt

A file at the root of a domain telling crawlers which paths they may fetch. Controls crawling, not indexing.

Schema.org

The shared vocabulary used by structured data, maintained collaboratively by the major search engines.

SERP

Search engine results page: everything returned for a query, including ads, maps, snippets and organic listings.

Sitemap

An XML file listing the addresses on a site that should be indexed, along with when each last changed.

Structured data

Machine-readable markup stating facts about a page, such as a business address or opening hours, usually as JSON-LD.

Thin content

A page with too little substance to answer a query usefully. Often a symptom of a page that does not fully address what the visitor wanted.

Title tag

The clickable headline for a page in search results, and the text on a browser tab. Distinct from the H1 heading.

Viewport meta tag

A line instructing mobile browsers to lay a page out at device width. Without it, phones render pages at desktop width and shrink them.