SEO glossary
The terms that come up in an SEO audit, defined in plain English. Thirty entries, no jargon used to explain other jargon.
A
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.
Related guide: Writing useful image alt text
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.
Related guide: AI and answer-engine readiness
C
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.
Related guide: Canonical links and duplicate content
Core Web Vitals
Google's measures of loading, interactivity and visual stability: Largest Contentful Paint, Interaction to Next Paint, and Cumulative Layout Shift.
Related guide: The viewport meta tag
Crawl budget
The number of pages a search engine will fetch from a site in a given period. Relevant mainly to large sites.
Related guide: XML sitemaps
Crawler
Software that fetches pages automatically to index them. Also called a bot or spider. Googlebot and Bingbot are the best known.
Related guide: robots.txt and crawler instructions
Cumulative Layout Shift
A Core Web Vital measuring how much page content moves around while loading. Commonly caused by images without declared dimensions.
Related guide: The viewport meta tag
D
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.
Related guide: Canonical links and duplicate content
F
Featured snippet
An answer extracted from a page and shown at the top of search results, above the ordinary listings.
Related guide: Structured data and rich results
H
H1
The top-level heading on a page, stating what the page is about. A page should normally have exactly one.
Related guide: Heading structure that makes sense
HTTPS
HTTP carried over an encrypted TLS connection. Required for the browser padlock and a lightweight ranking signal.
Related guide: Serving your site over HTTPS
I
Indexing
The process of storing a fetched page so it can be returned in results. A page can be crawled without being indexed.
Related guide: robots.txt and crawler instructions
J
JSON-LD
The recommended format for structured data: a block of JSON in a script tag describing the page using schema.org vocabulary.
Related guide: Structured data and rich results
L
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.
Related guide: AI and answer-engine readiness
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.
Related guide: Structured data and rich results
M
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.
Related guide: Meta descriptions that earn the click
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.
Related guide: The viewport meta tag
N
NAP
Name, address and phone number. Consistency across your site and third-party listings supports local ranking.
Related guide: Structured data and rich results
Noindex
A directive telling search engines not to include a page in results. Must be readable by the crawler, so the page can't also be blocked in robots.txt.
Related guide: robots.txt and crawler instructions
O
Open Graph
Meta tags controlling how a link appears when shared on social platforms and in messaging apps.
Related guide: Open Graph and social previews
Organic results
Listings earned through relevance rather than paid for. Distinct from the advertisements above and beside them.
Related guide: Writing title tags that earn clicks
R
Rich result
A search listing enhanced with extra detail such as ratings, prices or opening hours, made possible by structured data.
Related guide: Structured data and rich results
robots.txt
A file at the root of a domain telling crawlers which paths they may fetch. Controls crawling, not indexing.
Related guide: robots.txt and crawler instructions
S
Schema.org
The shared vocabulary used by structured data, maintained collaboratively by the major search engines.
Related guide: Structured data and rich results
SERP
Search engine results page: everything returned for a query, including ads, maps, snippets and organic listings.
Related guide: Writing title tags that earn clicks
Sitemap
An XML file listing the addresses on a site that should be indexed, along with when each last changed.
Related guide: XML sitemaps
Structured data
Machine-readable markup stating facts about a page, such as a business address or opening hours, usually as JSON-LD.
Related guide: Structured data and rich results
T
Thin content
A page with too little substance to answer a query usefully. Often a symptom of a page that doesn't fully address what the visitor wanted.
Related guide: Thin content, and what to do about it
Title tag
The clickable headline for a page in search results, and the text on a browser tab. Distinct from the H1 heading.
Related guide: Writing title tags that earn clicks
V
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.
Related guide: The viewport meta tag
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