SEO Glossary UK – A–Z of SEO Terms Defined

A B C D E F G H I J K L M N O P R S T U W X Z

Algorithm: A set of rules and calculations search engines use to determine the relevance and ranking order of web pages for any given query. Google's core algorithm uses hundreds of signals and is updated thousands of times per year.
Algorithm Update: A change to a search engine's ranking algorithm, ranging from minor tweaks to major named updates (Panda, Penguin, Helpful Content) that significantly shift which pages rank for which queries. See our SEO Basics guide for more context.
Alt Text (Alt Attribute): HTML attribute added to image tags describing the image content in text form. Essential for image SEO, accessibility for screen reader users, and providing context to search engines that cannot "see" images directly.
Anchor Text: The visible, clickable text of a hyperlink. Anchor text signals to search engines what the linked page is about. Exact-match anchor text (matching the target keyword) passes strong topical signals but should be used sparingly to avoid over-optimisation penalties.
Authority: A measure of how much trust and credibility a website or page has in the eyes of search engines, primarily determined by the quality and quantity of backlinks pointing to it. High authority sites rank more easily for competitive terms.
AMP (Accelerated Mobile Pages): An open-source HTML framework developed by Google to create fast-loading mobile web pages. AMP is no longer a requirement for Top Stories inclusion in Google News — Core Web Vitals performance has replaced it as the primary mobile speed ranking signal.

Backlink: A hyperlink from one website pointing to another. Backlinks from authoritative, relevant websites are among the strongest ranking signals in Google's algorithm — each acts as a "vote of confidence" for the linked page. Covered in depth in our Link Building guide.
Black Hat SEO: SEO techniques that violate search engine guidelines — including buying backlinks, keyword stuffing, cloaking, and using private blog networks. Black hat tactics may produce short-term gains but risk severe penalties including complete removal from search indexes.
Bounce Rate: In GA4, "bounce" is measured differently from Universal Analytics — a session that lasts under 10 seconds with no interaction or conversion is considered a bounce. High bounce rates can indicate content-intent mismatch or poor user experience.
Breadcrumb Navigation: A secondary navigation element showing a user's location within a website hierarchy (Home → Category → Page). Breadcrumbs aid user navigation, improve internal linking, and can appear in Google SERPs when BreadcrumbList schema is implemented.

Canonical Tag (rel="canonical"): An HTML link element that tells search engines which URL is the "preferred" version when multiple URLs contain similar or identical content. Prevents duplicate content issues from diluting ranking signals across multiple page variants.
Crawl Budget: The number of pages Googlebot crawls on your site within a given time period. Large sites must optimise crawl budget by blocking low-value pages and improving site speed so important content is discovered and indexed efficiently.
Click-Through Rate (CTR): The percentage of users who click on your search result after seeing it in SERPs. Calculated as clicks ÷ impressions × 100. Higher CTR is influenced by compelling title tags and meta descriptions. CTR data is available in Google Search Console.
CLS (Cumulative Layout Shift): A Core Web Vitals metric measuring visual stability — how much page elements shift unexpectedly during loading. Target score: under 0.1. Caused by images without specified dimensions, dynamically injected content, and late-loading fonts. See our Technical SEO guide.
Content Cluster: A group of interlinked content pieces covering a broad topic comprehensively — one pillar page targeting a head keyword supported by multiple cluster pages targeting related long-tail subtopics. Topic clusters build topical authority.
Core Web Vitals: Google's set of real-world user experience metrics — LCP (loading), INP (interactivity), and CLS (visual stability) — that are official ranking factors. Measured from real Chrome user data via the Chrome UX Report (CrUX).
Crawling: The process by which search engine bots (spiders/crawlers) systematically browse the web, following hyperlinks from page to page to discover new and updated content to add to their index. The first step before indexing and ranking.
ccTLD: Country Code Top-Level Domain — a domain extension specific to a country (.co.uk for UK, .de for Germany, .fr for France). Using a ccTLD is the strongest possible geotargeting signal for international SEO targeting a specific country.

Domain Authority (DA): A metric developed by Moz (1–100 scale) predicting how well a domain will rank based on its backlink profile. Not a Google metric — Google does not use Domain Authority as a ranking factor. Useful as a comparative benchmark but not an absolute measure of SEO performance.
Domain Rating (DR): Ahrefs' equivalent of Domain Authority — a logarithmic scale (0–100) measuring the strength of a domain's backlink profile relative to all other websites in their database. Higher DR correlates with greater ranking potential.
Disavow: A tool in Google Search Console allowing you to tell Google to ignore specific backlinks when assessing your site. Used to neutralise toxic or spammy links, particularly after a manual penalty for unnatural links. Should be used cautiously — incorrectly disavowing legitimate links can hurt rankings.
Dwell Time: The amount of time a user spends on a page after clicking through from a search result before returning to the SERP. Longer dwell time generally indicates content that satisfies the user's query. Not a confirmed direct ranking factor but correlates with content quality signals.

E-E-A-T: Experience, Expertise, Authoritativeness, Trustworthiness — Google's quality framework used by Search Quality Raters to evaluate content quality. Especially important for YMYL topics. Demonstrated through author credentials, accurate content, authoritative backlinks, and site-level trust signals. See our Content SEO guide.
External Link: A hyperlink on your website pointing to a different domain. External links to authoritative, relevant sources signal to search engines that your content is well-researched and connected to the broader web of information on a topic.

Featured Snippet: A special search result displayed at the top of Google SERPs (position zero) that directly answers a query by extracting a text paragraph, list, or table from a web page. Featured snippets are primary sources for voice search answers and earn significantly higher CTR than standard results.
Footer Links: Links placed in the footer of a website, typically appearing across all pages. Footer links pass less link equity than contextual in-content links and should not be used as a substitute for proper internal linking. Excessive footer links to manipulate anchor text is a known black hat signal.

Google Business Profile (GBP): Formerly Google My Business — a free business listing managed by Google that appears in Maps and local search results. Fully optimising your GBP is the most important local SEO action for any business with a physical location or local service area. See our Local SEO guide.
Google Search Console (GSC): A free Google tool that provides data on how Google crawls, indexes, and ranks your website. Shows search queries, impressions, CTR, positions, indexation status, Core Web Vitals, backlinks, and alerts for manual actions or security issues. Essential for all SEO work.
Googlebot: Google's web crawler — the automated programme that visits websites to discover and index content. Googlebot follows hyperlinks, downloads page content, and reports back to Google's indexing systems. There are separate Googlebot user agents for desktop and smartphone crawling.
Grey Hat SEO: SEO techniques that are not clearly defined as acceptable or unacceptable by search engine guidelines — occupying the space between clearly white hat and clearly black hat practices. Risk level varies; what is grey hat today may become clearly black hat after future algorithm updates.

HARO (Help A Reporter Out): Now rebranded as Connectively — a platform connecting journalists seeking expert sources with people who can provide quotes. A highly effective white-hat link building strategy for earning backlinks from major media publications. Covered in our Link Building guide.
Heading Tags (H1–H6): HTML elements that define the hierarchical structure of content on a page. H1 is used once per page for the primary topic, H2 for major sections, H3 for subsections. Heading structure helps both users skim content and search engines understand content organisation.
Hreflang: An HTML attribute that specifies the language and optional country target for a web page, enabling search engines to serve the correct language or regional version to users in different markets. Essential for international SEO. See our International SEO guide.
HTTPS: HyperText Transfer Protocol Secure — an encrypted version of HTTP that protects data transmitted between browsers and servers. HTTPS is a confirmed Google ranking signal. All websites should use HTTPS with a valid SSL/TLS certificate; browsers flag non-HTTPS sites as "Not Secure."

Index: Google's massive database of web pages it has discovered, processed, and stored. A page must be in Google's index to appear in search results. Not all crawled pages are indexed — Google may exclude thin content, duplicate pages, or pages with noindex directives.
INP (Interaction to Next Paint): A Core Web Vitals metric measuring the responsiveness of a page to user interactions — specifically how quickly the browser renders visual feedback after a user clicks, taps, or keyboard interaction. Target: under 200ms. Replaced FID as an official Core Web Vital in March 2024.
Internal Link: A hyperlink connecting one page on a website to another page on the same website. Internal links help search engines discover content, distribute link equity throughout the site, and signal topical relationships between pages. A strong internal linking strategy is a high-leverage zero-cost SEO tactic.

Keyword: A word or phrase that users type into search engines when looking for information, products, or services. SEO involves identifying keywords relevant to your content, analysing their search volume and competition, and optimising pages to rank for them.
Keyword Cannibalization: When multiple pages on the same website compete for the same keyword, diluting ranking potential and confusing search engines about which page to rank. Fixed through content consolidation, canonical tags, or content differentiation. Covered in our Keyword Research guide.
Keyword Density: The percentage of times a keyword appears in a piece of content relative to total word count. An outdated concept — modern SEO focuses on semantic relevance and topical comprehensiveness rather than keyword density. Over-repetition of keywords (keyword stuffing) is a ranking penalty signal.
Keyword Difficulty (KD): A metric (typically 0–100) estimating how hard it is to rank on the first page for a given keyword, based on the backlink authority of currently ranking pages. Available in tools like Ahrefs and SEMrush. Low KD keywords are prioritised by new sites building initial authority.

LCP (Largest Contentful Paint): A Core Web Vitals metric measuring loading performance — specifically how quickly the largest visible element on the page (image, video, or text block) becomes visible to the user. Target: under 2.5 seconds. One of the most important page speed metrics for SEO.
Link Equity (PageRank): The SEO value passed from one page to another through hyperlinks. High-authority pages pass more equity than low-authority pages. Do-follow links pass equity; no-follow links do not (though they still have traffic and discovery value). Also called "link juice" informally.
Local Pack: The block of 3 local business listings (with a map) that appears at the top of Google search results for queries with local intent. Also called the "map pack" or "3-pack." Ranking in the local pack requires Google Business Profile optimisation and strong local signals.
Long-Tail Keyword: A specific, typically longer search phrase (3+ words) with lower individual search volume but also lower competition and clearer intent than broad "head" keywords. Long-tail keywords collectively account for the majority of all searches and are particularly valuable for new sites. See our Keyword Research guide.

Meta Description: An HTML meta tag providing a brief summary of a page's content, displayed beneath the title tag in search results. Not a direct ranking factor but significantly influences click-through rate. Recommended length: 150–160 characters. See our On-Page SEO guide.
Mobile-First Indexing: Google's approach of using the mobile version of a website as the primary version for crawling, indexing, and ranking — since most searches now happen on mobile devices. Active for all websites since 2023. Sites must ensure their mobile version contains equivalent content to desktop. See our Mobile SEO guide.

NAP: Name, Address, Phone Number — the three core pieces of business information that must be consistent across all online platforms for effective local SEO. NAP inconsistencies confuse search engines and negatively impact local rankings. See our Local SEO guide.
No-Follow (rel="nofollow"): A link attribute instructing search engines not to pass link equity (PageRank) through a hyperlink. Used for paid links, user-generated content links, and links to untrusted pages. Introduced by Google in 2005 to combat comment spam. In 2019 Google made nofollow a "hint" rather than a directive.
No-Index: A directive (via meta robots tag or X-Robots-Tag HTTP header) instructing search engines not to include a page in their index. Used for duplicate pages, thin content, admin pages, and other URLs that should not appear in search results.

Off-Page SEO: SEO activities performed outside your own website to improve rankings — primarily link building, but also brand mentions, digital PR, social signals, and online reputation management. Off-page signals indicate your site's authority and trustworthiness to search engines.
On-Page SEO: Optimisations made directly on individual web pages to improve their ranking — title tags, meta descriptions, headings, content quality, keyword placement, internal links, images, URL structure, and structured data. Covered comprehensively in our On-Page SEO guide.
Organic Traffic: Website visitors who arrive via unpaid (organic) search results, as opposed to paid ads (PPC). Organic traffic is often the highest-quality and highest-converting traffic source because users are actively seeking information or solutions related to your content.
Orphan Page: A page on a website that has no internal links pointing to it from any other page on the site. Orphan pages are difficult for search engines to discover and fail to receive any link equity from the rest of the site. Identified via site crawl tools like Screaming Frog.

PageRank: Google's original algorithm (named after co-founder Larry Page) that assigned a numerical score to web pages based on the quantity and quality of links pointing to them. While Google no longer publicly reveals PageRank scores, the underlying concept of link equity flowing between pages remains central to how Google ranks content.
Pillar Page: A comprehensive, authoritative page covering a broad topic in substantial depth, designed to rank for a high-volume head keyword and act as a hub linking to multiple related cluster pages. Pillar pages are central to topic cluster content architecture. See our Content SEO guide.
Position Zero: The featured snippet result displayed above standard organic results in Google SERPs, occupying the most prominent position on the page. Position zero generates high CTR for informational queries and is the primary source of voice search answers. Pages ranking positions 1–5 can win position zero without being the #1 organic result.

Redirect (301 / 302): Instructions that send users and search engines from one URL to another. 301 (Permanent) redirects pass link equity and tell Google to update its index. 302 (Temporary) redirects do not pass link equity. Using 302 when you intend 301 is a common technical SEO mistake. See our Technical SEO guide.
Rich Results: Enhanced search results featuring additional visual elements beyond the standard blue link — star ratings, FAQ dropdowns, how-to steps, recipe cards, event dates. Rich results are triggered by structured data (schema markup) and typically achieve higher CTR than standard results.
Robots.txt: A text file at the root of a website (yourdomain.com/robots.txt) that provides instructions to web crawlers about which pages they should or should not access. Used to prevent crawling of admin pages, duplicate pages, and low-value URL patterns. Note: robots.txt prevents crawling but does not guarantee pages are not indexed.

Schema Markup (Structured Data): Code (typically JSON-LD format) added to pages that explicitly communicates content meaning to search engines using a standardised vocabulary from Schema.org. Enables rich results and helps search engines and AI systems accurately understand and surface your content. Covered in our Technical SEO guide.
Search Intent: The underlying goal or motivation behind a search query — what the searcher actually wants to find or accomplish. The four primary intent types are: Informational, Navigational, Commercial, and Transactional. Aligning content format and depth to match search intent is essential for ranking. See our Keyword Research guide.
SERP: Search Engine Results Page — the page displayed by a search engine in response to a query. Modern SERPs contain a mix of features: organic results, featured snippets, local pack, video carousels, shopping results, People Also Ask boxes, knowledge panels, and paid ads.
Sitemap (XML): A file listing all important URLs on a website, submitted to search engines via Google Search Console and Bing Webmaster Tools. Sitemaps help search engines discover and efficiently crawl your content. Should only include canonical, indexable URLs and be updated whenever pages are added or removed.

Technical SEO: The practice of optimising a website's infrastructure — crawlability, indexability, site speed, mobile-friendliness, structured data, security (HTTPS), and URL architecture — to help search engines efficiently access, understand, and rank your content. See our Technical SEO guide.
Title Tag: An HTML element specifying a page's title, displayed as the clickable headline in search results. The most important on-page SEO element — it should contain the primary keyword within the first 60 characters, be unique for every page, and be compelling enough to earn clicks. See our On-Page SEO guide.
Topical Authority: The perceived expertise and comprehensive coverage of a specific subject that a website builds over time through in-depth, interconnected content. Websites with strong topical authority tend to rank more easily for all keywords related to their core topic area, regardless of individual page-level optimisation.
TTFB (Time to First Byte): The time from when a browser requests a page to when it receives the first byte of response from the server. A measure of server responsiveness. Target: under 800ms. Poor TTFB is typically caused by slow hosting, no caching, or database query overhead — improving it requires hosting-level changes.

URL Structure: The format and organisation of web page addresses. SEO-friendly URLs are lowercase, use hyphens to separate words, contain the primary keyword, and are as short and descriptive as possible. Avoid URL parameters, numbers, and excessive subfolders where possible.
User Experience (UX): The overall quality of a user's interaction with a website — encompassing page speed, mobile responsiveness, navigation clarity, content readability, and visual design. Google increasingly factors UX quality (via Core Web Vitals and Page Experience signals) into ranking decisions.

White Hat SEO: SEO techniques that follow search engine guidelines and focus on creating genuine value for users — quality content, honest link earning, proper technical implementation. White hat SEO produces sustainable, long-term ranking improvements without risk of penalties.
WebP: A modern image format developed by Google that provides superior compression compared to JPEG and PNG at equivalent visual quality, reducing file sizes by 25–35%. Using WebP images improves page load speed and LCP scores. Supported by all modern browsers.

XML Sitemap: A structured XML file listing all important URLs on your website, designed for search engine crawlers rather than human readers. Submit your XML sitemap to Google Search Console and Bing Webmaster Tools to help search engines discover and efficiently crawl all your content.

Zero-Click Search: A search query where the user gets their answer directly on the SERP — from a featured snippet, knowledge panel, local pack result, or AI Overview — without clicking through to any website. Zero-click searches represent a growing share of queries, making featured snippet optimisation and brand visibility increasingly important.
Zero-Volume Keywords: Keywords that show 0–10 monthly searches in keyword research tools but still attract real visitors due to underreporting by tools or because they represent highly specific niche queries. Zero-volume keywords often have very high conversion rates due to extreme specificity of intent and near-zero competition.

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