Glossary
The terms we use on this site, defined in a sentence or two. Where a word means two different things depending on who says it, we say so.
AI crawler
A program that walks the web on behalf of a model operator. Three very different purposes coexist: training a model, feeding an answer engine, or fetching one page a user has just asked for.
See also: robots.txt, User agent, Answer engine
Where you can see it: AI crawler directory
Anchor text
The clickable text of a link. It tells an engine what sits on the other side; an unnaturally uniform anchor distribution across inbound links reads as manipulation.
See also: Backlink, Internal linking
Where you can see it: Backlink analysis
Answer engine
An interface that answers a natural-language question instead of returning a list of links: ChatGPT, Gemini, Perplexity, Copilot. The answer usually cites sources, and being among them is the new visibility question.
See also: GEO (generative engine optimization), Share of citations, AI crawler
Where you can see it: AI visibility audit
Backlink
A link pointing at your site from another domain. Its value depends far more on the domain that emits it and the context of the page than on the total count of links.
See also: Referring domain, Spam score, Anchor text
Where you can see it: Backlink analysis
Canonical URL
A declaration in a page stating which address should be treated as the reference version when several URLs serve the same content. It is a hint, not a directive: an engine may ignore it if it looks inconsistent.
See also: Duplicate content, hreflang, Indexing
Click depth
The smallest number of links you have to follow from the home page to reach a given page. Greater depth correlates with rarer crawling, provided it is measured on the site’s real links rather than on an injected sitemap.
See also: Internal linking, Orphan page, Crawl budget
Where you can see it: Technical SEO audit
CLS (cumulative layout shift)
How much a page moves under the reader while it loads. The published reference threshold is 0.1.
See also: Core Web Vitals, LCP (largest contentful paint), INP (interaction to next paint)
Contrast ratio
The luminance ratio between text and its background. WCAG 2.2 level AA asks for 4.5:1 on body text and 3:1 on large text, those are standards thresholds, not product measurements.
Where you can see it: Accessibility audit
Core Web Vitals
Three loading-experience metrics published by Google: LCP for how fast the main content appears, CLS for visual stability, INP for responsiveness to interaction.
See also: LCP (largest contentful paint), CLS (cumulative layout shift), INP (interaction to next paint)
Crawl budget
How many pages an engine is willing to crawl on a site in a given period. It is not contractual: you infer it from behaviour observed in server logs, never from an announced figure.
See also: Server log, Click depth, Ghost page
Where you can see it: SEO log file analysis
Duplicate content
The same content served under several addresses. The cost is not a penalty but dilution: signals split across the URLs, and the engine picks one itself.
See also: Canonical URL, hreflang
EAA (European Accessibility Act)
An EU directive making accessibility mandatory across a broad set of digital products and services. It applies through national transposition, so deadlines and penalties differ by member state.
Where you can see it: Accessibility audit
Gap analysis
Cross-referencing your link or keyword profile against competitors to isolate what cites or ranks them and not you. It produces a target list, not a diagnosis.
See also: Backlink, Referring domain
Where you can see it: Backlink analysis
GEO (generative engine optimization)
The practices aimed at being cited by answer engines. The vocabulary has not settled: some people say "AEO" or "AI SEO" for roughly the same thing.
See also: Answer engine, llms.txt, Share of citations
Where you can see it: AI visibility audit
Ghost page
A page your server logs show being crawled although it appears in no crawl of the site. Usually a removed URL, a forgotten parameter, or an inbound link from a third party.
See also: Server log, Orphan page, Crawl budget
Where you can see it: SEO log file analysis
hreflang
A declaration linking the language versions of the same page. It has to be reciprocal: page A declaring B without B declaring A is ignored.
See also: Canonical URL, Duplicate content
Indexing
Whether a crawled page is kept in an engine’s index and therefore eligible to be shown. Crawled is not indexed: an engine can read a page and decide not to keep it.
See also: Search Console, Canonical URL, Sitemap
Where you can see it: Technical SEO audit
INP (interaction to next paint)
The delay between a visitor’s interaction and the next visible paint. It replaced FID as the Core Web Vitals responsiveness metric; the published reference threshold is 200 ms.
See also: Core Web Vitals, LCP (largest contentful paint), CLS (cumulative layout shift)
Internal linking
The links a site points at its own pages. They decide what an engine reaches, how often, and how value spreads between pages.
See also: Click depth, Orphan page, Internal PageRank
Where you can see it: NessFlow vs Screaming Frog
Internal PageRank
A model of how value flows from a page to the pages it links. Recomputed on a site’s internal graph alone, it ranks pages against each other, it says nothing about how an engine values them.
See also: Internal linking, Click depth
Where you can see it: NessFlow vs Screaming Frog
JavaScript rendering
Executing a page’s JavaScript before analysing its content. Without it a tool reads the initial HTML (often nearly empty on a modern application), and wrongly concludes the page has no content.
See also: SPA (single-page application), Crawl budget
Where you can see it: Technical SEO audit
LCP (largest contentful paint)
How long before the largest visible element of the page is painted. It is the perceived-speed metric of Core Web Vitals; the published reference threshold is 2.5 s.
See also: Core Web Vitals, CLS (cumulative layout shift), INP (interaction to next paint)
llms.txt
A text file at the root of a domain that introduces the site to answer engines in a model-readable form. It is not an official standard: no operator commits to reading it.
See also: GEO (generative engine optimization), robots.txt, Answer engine
Where you can see it: robots.txt for AI crawlers: the complete configuration, crawler by crawler
Mixed content
An HTTPS page loading a resource over HTTP. Browsers block or downgrade those resources, so what the visitor sees is a broken page rather than a warning.
See also: Structured data
Orphan page
A page with no inbound link from the site itself. Engines may still know it from a sitemap or an external link, but nothing in the navigation leads there.
See also: Internal linking, Click depth, Ghost page
Where you can see it: Server log analysis: what your servers know and Search Console does not
Referring domain
A distinct domain pointing at least one link at your site. This is the unit that counts: a hundred links from one domain are not a hundred domains.
See also: Backlink, Spam score, Gap analysis
Where you can see it: Backlink analysis
RGAA
The French accessibility framework, a national derivation of the WCAG criteria. It adds a test method and a conformance declaration format that carry legal weight in France.
See also: WCAG, EAA (European Accessibility Act), VPAT
Where you can see it: Accessibility audit
robots.txt
A file at the root of a domain declaring what each crawler may fetch. Groups do not stack: a crawler applies only the most specific group that names it.
See also: AI crawler, User agent, Crawl budget
Where you can see it: robots.txt for AI crawlers: the complete configuration, crawler by crawler
Search Console
Google’s interface giving impressions, clicks and indexing status for a verified property. Its numbers are sampled and rounded: treat them as orders of magnitude, not accounting.
See also: Indexing, SERP, Server log
Where you can see it: NessFlow vs Botify & Oncrawl
Semantic coverage
A measure of how many of the notions expected on a topic actually appear in a text. It shows what a piece is missing; it does not say whether the piece is good.
See also: Structured data
Where you can see it: Semantic optimisation
SERP
A search engine results page for a given query. It varies with location, language and device: a ranking only means something alongside those three parameters.
See also: SERP feature, Search Console
Where you can see it: Rank tracking
SERP feature
Any block of a results page that is not a blue link: featured snippet, people-also-ask, image carousel, AI-generated overview. Their presence moves clicks far more than rank itself.
See also: SERP, Answer engine
Where you can see it: Rank tracking
Server log
The file where a server records every request it receives. It is the only source that says what engines actually asked for, as opposed to what a tool assumes they do.
See also: Crawl budget, Ghost page, Search Console
Where you can see it: SEO log file analysis
Sitemap
An XML file listing the URLs a site wants crawled. It is a suggestion: being listed guarantees neither crawling nor indexing, and being absent forbids neither.
See also: Indexing, Orphan page, Click depth
SPA (single-page application)
A web application that navigates without full page reloads, with the browser building the content. This is where JavaScript rendering stops being a convenience and becomes a condition for being crawled at all.
See also: JavaScript rendering, Click depth
Where you can see it: JavaScript SEO: getting a single-page app crawled
Spam score
A vendor-supplied index estimating how likely a referring domain is to be artificial. It is a proprietary estimate, not an engine’s verdict.
See also: Backlink, Referring domain
Where you can see it: Backlink analysis
Structured data
Markup describing what a page’s content means in a format engines interpret. Markup describing something other than what the page shows loses the rich result it existed to win.
See also: SERP feature, Indexing
User agent
The string a client sends to identify itself to a server. It is declarative and trivially forged: blocking on it alone stops the honest crawlers and nobody else.
See also: AI crawler, robots.txt, Server log
Where you can see it: AI crawler directory
VPAT
A standardised US-originated document in which a vendor states how far its product conforms to accessibility criteria. It is a supplier declaration, not an independent certification.
See also: WCAG, RGAA, EAA (European Accessibility Act)
Where you can see it: Accessibility audit
WCAG
The international Web Content Accessibility Guidelines, organised into testable criteria and three conformance levels (A, AA, AAA). Version 2.2 is the current reference.
See also: RGAA, VPAT, Contrast ratio
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