Glossary Web & SEO

The terms

37 terms · in alphabetical order

AI Overviews

The AI-generated answer shown at the top of Google results. It summarizes several sources and cites them. Opting out of it without leaving Google is impossible: both run on the same index. Being cited in an answer does not depend on the page's ranking, but on the quality of the selected passage.

Analytics

The tools that measure a site's audience: visits, page views, traffic sources, user journeys. Google Analytics is the most common; Matomo and Plausible are alternatives. In France, the CNIL regulates these tools: strictly limited audience measurement can be exempt from consent, while a tool also used for advertising cannot.

Astro

A site generator that outputs static HTML and sends no JavaScript to the browser by default. The result: light pages, fast to load and readable without running any script, which also matters for answer engines, many of which do not render JavaScript when fetching a page.

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Backlink

A link pointing to your site from a third-party site. Long the currency of SEO, it remains a trust signal when it is editorial and relevant. Answer engines use it less to rank than to verify an entity: a mention in a directory or a press article confirms that it exists.

Bounce rate

The share of visits that leave a site after a single page. A bounce is not always a failure: reading a full page and leaving can be a successful visit, but when loading is slow, a bounce is an abandonment. The probability of bounce rises by 32% as load time goes from one to three seconds (Think with Google, 2017).

Canonical

The tag that declares the official URL of a page when the same content is reachable at several addresses. It stops the engine from splitting a page's credit across duplicates. It must be absolute and point to itself on every page.

CMS

Content Management System: software that lets you edit a site without touching code, such as WordPress. The comfort has a cost: a CMS runs code on every visit, relies on plugins that need maintenance, and must be updated or it becomes vulnerable. A static site trades that comfort for speed and no maintenance.

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Conversion

A useful action taken by a visitor: a call, a submitted form, a quote request, a purchase. The conversion rate relates these actions to the number of visits. It is the metric that links a site to revenue: more traffic without more conversions changes nothing for a business.

Core Web Vitals

The three metrics Google uses to measure the real experience of a page: LCP for loading speed, INP for responsiveness to interactions, and CLS for visual stability. They are measured on real visits by Chrome users, not in a lab.

Crawl

The automatic reading of a page by a bot in order to add it to an index. Crawling is the front door: a page that is misconfigured, slow or behind a JavaScript challenge may never be read. An overly strict robots.txt or a badly tuned firewall is enough to make a site invisible, with no error message at all.

CrUX

Chrome User Experience Report: the public database of performance measurements collected on real visits by Chrome users. It is what feeds the Core Web Vitals. A site without enough traffic is not in it yet, like this one: that is why I publish my lab measurements, dated and reproducible.

Cumulative Layout Shift (CLS)

A measure of a page's visual stability: how much elements move around while it loads. A score under 0.1 is good. CLS typically gets worse when an image or a font arrives late without its space having been reserved. It is one of the three Core Web Vitals.

Domain name

A site's readable address, such as web-consulting.fr. It is rented from a registrar, yearly, and renewed. The key point is ownership: the domain must be registered in the business's name, not its provider's; otherwise, changing provider can mean losing your address and your emails.

GEO (Generative Engine Optimization)

Optimizing a site to be cited in the answers generated by AI engines such as ChatGPT, Perplexity or Google AI Overview. Where SEO aims at ranking in the results list, GEO aims at being cited inside the answer itself. Both rest on the same base: factual, dated, attributed and technically accessible content.

Google Business Profile

The free business listing shown on Google Maps and in the local panel of search results. It is the main lever of local SEO: a complete listing, with photos, opening hours and reviews, captures "near me" searches. It exists independently of the website, and both must say exactly the same thing.

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Hosting

The service that stores a site's files on a server permanently connected to the internet, so it can answer every visit. Its quality affects speed (TTFB), availability and security. A static site can be served by a CDN, a network of distributed servers that brings files closer to visitors.

Hreflang

The tag that tells Google which version of a page matches which language and country. It prevents the English version of a site from showing up for a French search. Every page must point to all its versions, and all of them must point back: that is reciprocity.

Hydration

The process by which a JavaScript framework turns a received page into an interactive application. A page that needs it is inert without JavaScript; a static page is fully readable before anything runs. The difference shows in loading time, and in how bots that do not run scripts read the page.

Indexing

The recording of a page in an engine's database, which makes it eligible to appear in results. Crawling is reading; indexing is shelving the book in the library. A crawled page is not always indexed; a page that is not indexed can never rank.

JSON-LD

The format used to write Schema.org structured data: a JavaScript Object Notation for Linked Data block in the page code, readable by machines without touching the visible content. It is the format Google recommends, over microdata or RDFa.

Largest Contentful Paint (LCP)

The time between the start of a page load and the display of its largest visible element. Google rates it good under 2.5 seconds and poor above 4. It is one of the three Core Web Vitals, measured on field data from the CrUX report, at the 75th percentile of visits.

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Lighthouse

Google's free, open-source page auditing tool. It scores performance, accessibility, best practices and SEO, each out of 100. A Lighthouse score is a lab measurement on a simulated connection: a reproducible thermometer, not the real temperature of your visitors.

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llms.txt

A file proposed in 2024 to summarize a site for AI agents. As of September 2026, no major answer engine has announced using it to choose its sources; its real use is developer tooling. Markdown mirrors of each page are mechanically better.

Local SEO

Ranking a business for location-based queries ("plumber Dijon"). It rests on three pillars: the Google Business Profile listing, consistent name, address and phone number across the site and directories, and reviews. A site can be invisible nationally and highly visible locally, and the other way round.

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NAP consistency

Name, Address, Phone: the accuracy of a business's name, address and phone number across its website, its Google Business Profile and directories. A mismatch is a reason to be left out: when two sources contradict each other, an answer engine prefers not to cite rather than risk a false statement.

Responsive design

A way of building a site so its layout adapts to screen size: phone, tablet, desktop. The content stays the same; its arrangement changes. Since Google indexes the mobile version of pages first (mobile-first indexing), a site that displays poorly on a phone is judged on its worst version.

RGAA

The Référentiel Général d'Amélioration de l'Accessibilité, France's digital accessibility standard. It has 106 criteria. Declaring a site "partially compliant" requires an audit; without one, the only honest statement is "non-compliant", even with an automated score of 100 out of 100.

robots.txt

A site's access control file, at the root of the domain. It tells crawlers what they may read and what they may not. Since 2025, AI companies separate their training crawlers from their search crawlers: blocking one does not remove you from the other.

Schema.org

The web's standard structured data vocabulary, co-written by Google, Microsoft, Yahoo and Yandex. It lets a page declare in JSON-LD what it is: a business, an article, a FAQ, a review. Engines use it to understand the entity behind the page instead of guessing it.

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SEO

Search Engine Optimization: the set of practices that make a site readable and well ranked by a search engine such as Google. It covers technical SEO (speed, structure, markup), content and link building. SEO never guarantees a position: it raises the likelihood of appearing for the right queries.

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SERP

Search Engine Results Page: the page of results returned by a search engine. In 2026 it combines a classic list of links with AI-generated answers, local panels and rich snippets. Being visible in the AI answer does not exempt you from being present in the list.

Sitemap

An XML file listing a site's pages to help engines discover them. It does not create rankings: it guarantees access. The HTML version, meant for humans, is the site map page. The last-modified date per page is only useful if it is honest.

Structured data

Information about information: markup that tells machines what a page contains, such as a business, a price, a question or a recipe. It does not create rankings, but it removes ambiguity, and ambiguity is what makes a page lose at the selection stage.

Time to First Byte (TTFB)

The time between requesting a page and receiving the first byte of the response. It mostly measures the server and the hosting, not the page. Under 800 milliseconds is considered good; a well-hosted static site is often under 300.

Traffic

The volume of visits a site receives over a period, often broken down by source: organic search, direct, social networks, referrals, ads. The number alone says little: a thousand visits from people not looking for your service are worth less than fifty who are. Read it alongside conversion, never on its own.

UX (user experience)

User Experience: how a visitor lives their time on a site, from first impression to action. It depends on clear copy, navigation, speed, mobile readability and accessibility. Good UX goes unnoticed: people find what they are looking for without having to think about it.

WordPress

The most used CMS on the web: over 40% of all websites according to W3Techs. It is flexible and rich in plugins, but runs server-side code on every visit and must be updated regularly; its plugins are the main entry point for website hacks.

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