Definitions beginning with C

C2PA

Open standard describing signed information about the origin and modifications of digital media.

In practice: Check provenance stays attached to the distributed file and do not infer truth from it.

Cache

Storage of reusable results to avoid repeated computation or transfer. In HTTP, a cache determines which response matches a request and whether reuse is permitted. Shared and private caches have different scopes; personalised data needs an appropriate policy.

Reference: RFC 9111 : HTTP Caching · Source consulted 2026-10-18

In practice: Check lifetime, purge method and behaviour after an urgent update.

Cache revalidation

Server check establishing whether a stored response can still be used. Successful validation can reuse existing content rather than transfer a complete new copy.

Reference: MDN : HTTP caching

Source consulted : MDN · 2026-10-17

Observe loading after expiry and after a content change, distinguishing reuse from a new transfer.

Cache-Control

HTTP header specifying storage and reuse directives. no-cache requires validation before reuse; no-store requests no storage; private restricts storage to private caches. These directives serve different needs and must match the content actually served.

Reference: MDN : Cache-Control · Source consulted 2026-10-18

In practice: inspect page and asset headers after release to avoid stale content.

CacheStorage

Browser interface organising Cache objects containing request-response pairs. This application storage differs from automatic HTTP caching; the application must manage updates.

Reference: MDN : CacheStorage

Source consulted : MDN · 2026-10-17

Change a resource and then the cache version; check what an older session shows offline.

Call to action

Element clearly inviting an action such as requesting a quote, purchasing, registering, calling or downloading.

In practice: state what happens after the click and check that the destination fulfils that promise.

Canonical URL

Preferred reference address for content accessible at several URLs. A canonical declaration signals a preference to search engines; it does not redirect visitors or guarantee the engine’s final selection.

Reference: Google Search Central : Canonical URLs · Source consulted 2026-10-21

In practice: align canonical URLs with links and the sitemap; the tag expresses a preference and does not replace a needed redirect.

CAPTCHA

Challenge intended to distinguish humans from automation. It can be bypassed and exclude users; assess both accessibility and effectiveness.

Reference: W3C · CAPTCHA accessibility · Group Draft Note · Source consulted 2026-10-31

In practice: Measure the burden on people and provide an accessible alternative before adding one.

Carbon-aware design

Design that reduces or shifts digital processing according to usefulness, energy cost and usage context.

In practice: Measure actual effects on resources and visitor tasks before claiming a benefit.

Catalogue facet

Structured entry property used to narrow or organise results, such as category, region or availability.

In practice: add a facet only when its data is reliable across the relevant entries.

CDN

A distributed network serving content from multiple locations. It can bring resources closer to visitors; check what is actually cached, its updates and personalised responses.

Reference: MDN : CDN · Source consulted 2026-10-18

In practice: test cache invalidation and page availability from several locations.

Certificate renewal

Obtaining a new certificate to maintain service continuity before the presented certificate expires.

Reference: Let’s Encrypt : Integration Guide

Check issuance, installation, reload and the certificate received at the entry point.

Chart description

Text conveying axes, values, relationships and trends needed to understand a chart without seeing it.

In practice: name the subject briefly, then provide trends and values in structured description.

Chatbot

Automated conversational interface answering questions or guiding a user through rules or artificial intelligence.

In practice: Test out-of-scope requests and offer a clear route to a person.

Checkout journey

Sequence from product page through basket, payment and confirmation to actual order handling; each state must agree for the buyer and the seller.

In practice: try an accepted order, a declined payment and a stock-out, then compare customer and team confirmations.

Chunking

Division of a document into units suited to indexing, retrieval and insertion into a model context.

In practice: Split at meaningful ideas and retain headings or references needed to understand each excerpt.

Claim register

Editorial register linking a page’s figures, dates, quotations and other important claims to sources, owners and next review dates.

In practice: take one published figure and locate its source, period, approver and next review date.

Click depth

Number of links followed from a defined starting point to reach a page. Depth helps examine a site structure but depends on the chosen route and does not measure usability by itself. Clear labels and task-appropriate journeys matter alongside the number of steps.

Reference: W3C WAI : Menus · Source consulted 2026-10-18

In practice: start from the homepage and then from a common landing page to find the same information. Observe hesitation and backtracking; removing a step does not help if the new menu makes the destination harder to understand.

Click-through rate

Click-through rate: proportion of people who clicked after seeing a link, advertisement or result.

In practice: compare the rate by page, query and context rather than site-wide.

Client

Software requesting resources or operations from a server, such as a browser. Client-side checks assist use but do not replace server-side verification.

Reference: MDN : Client-server overview · Source consulted 2026-10-18

In practice: Specify whether this means a browser, application or customer before describing a problem.

Cloud computing

On-demand delivery of shared computing resources such as compute, storage, databases or applications.

In practice: Compare recurring costs, data location and exit options before moving a service.

CMS

Content Management System: software for creating, organizing and publishing content without editing every page manually.

In practice: ask the future publishing team to create, correct, translate and export a real page.

CNAME

DNS record type making one name an alias of another, the canonical target. Resolution follows that target to find required data. A CNAME contains neither a page path nor an HTTP redirect rule: pointing a subdomain does not by itself change the address displayed in the browser.

Reference: IETF : RFC 1034, Domain Names · Source consulted 2026-10-18

In practice: distinguish the source name, target name and visitor-facing URL. Check existing records and service requirements before changes; successful resolution does not validate the certificate or page subsequently served.

Comparable criterion

Characteristic defined consistently for each product to support a fair comparison.

In practice: measure every product using the same definition.

Comparison table

Presentation aligning several products against defined criteria to make differences understandable.

In practice: keep headers associated with values on a phone.

Component state

An interface element’s condition, such as selected, expanded, unavailable or busy. Make it perceivable and consistent with behaviour; a colour change alone does not explain available actions.

Reference: W3C APG : Keyboard interface · Source consulted 2026-10-18

In practice: plan focus, error and unavailable states before publishing a control.

Compression

Transformation reducing data to store or transmit. HTTP compression and image-format compression operate at different levels. Compare transfer size, processing cost and useful quality; recompressing an already compressed file does not necessarily yield savings.

Reference: MDN : Compression in HTTP · Source consulted 2026-10-18

In practice: measure actual transfer size of text and images without losing useful quality.

Conditional request

HTTP request containing a condition, such as a known ETag. The server evaluates it when choosing a response; a 304 result can avoid retransmitting unchanged content.

Reference: MDN : HTTP conditional requests

Source consulted : MDN · 2026-10-17

Prepare a satisfied and an unsatisfied condition; compare result, body and expected response.

Confirmation email

Message sent after an action to confirm its real status and explain what happens next.

In practice: confirm only what was actually recorded.

Consent Mode

Google mechanism adapting the behavior of certain measurement tags according to user consent choices.

In practice: Check which signals change after a choice and distinguish observed from modelled data.

Content Credentials

Provenance information attached to media to indicate its creator, tools and certain verifiable transformations.

In practice: Inspect what the metadata actually attests and how it survives edits.

Content decay

Gradual loss of usefulness, accuracy, visibility or performance when content no longer fits its topic or audience.

In practice: compare demand, visibility and usefulness before deciding to change a page.

Content freshness

Degree to which a page still reflects current facts, dates, practices, links and expectations for its topic.

In practice: Review facts that have changed first rather than changing a date without a useful update.

Content gap

Useful topic, question or intent that a website’s existing content does not yet cover properly.

In practice: find a real unanswered question rather than a keyword variant.

Content inventory

Register of a website’s pages and media recording URL, purpose, owner, status and decisions to retain or update them.

In practice: assign each page an owner, a status and a decision: retain, improve, merge, redirect or retire.

Content lifecycle

Stages through which content is managed: preparation, approval, publication, review and eventual removal or archiving according to usefulness. This lifecycle requires ownership and update criteria. A publication date alone does not determine whether information remains accurate, relevant and accessible.

Reference: W3C WAI : Planning and managing · Source consulted 2026-10-18

In practice: assign an owner and review triggers to a sensitive page, such as a price or opening-hours change. On removal, check incoming links and provide a useful destination for visitors retaining its address.

Content marketing

Strategy attracting and supporting an audience through useful content rather than purely promotional messages.

In practice: Connect each topic to a real audience question and a useful next step after reading.

Content owner

Person responsible for approving accuracy, publication and updates for content or a set of pages.

In practice: name who approves changes and receives correction requests.

Content provenance

Set of elements documenting a piece of content’s origin, author, date, sources and transformations.

In practice: retain source, date, author and usage rights for important claims and media.

Content pruning

Review of a content set leading to improvement, consolidation, redirection, deindexing or removal of content that is no longer useful.

In practice: Check visits, links, usefulness and redirect needs before removing a page.

Content replacement

New page or resource genuinely meeting the same need as removed content.

In practice: redirect only to a page meeting the same need.

Content trust

Trust created by accurate, attributed, dated and consistent information supported by appropriate evidence.

In practice: Show the source, method and person responsible for important claims.

Conversion

Action considered valuable to the business, such as a purchase, enquiry, booking, registration or download.

In practice: define an action that represents real progress, then verify its tracking end to end.

Conversion funnel

Representation of successive steps leading to an intended action, such as an enquiry or booking. Analysis counts progression according to defined rules. The model simplifies real journeys that may be nonlinear; an exit alone does not prove a defect or permanent abandonment by a person.

Reference: Google Analytics : Funnel exploration · Source consulted 2026-10-18

In practice: define events, their order and the observation period before comparing steps. Specify whether entry is allowed partway through and check duplicate events; measurement errors can appear to show visitor loss.

Conversion rate

Share of visits, sessions or people completing a defined action, depending on the chosen denominator. For example, 20 enquiries from 500 visits is 4%. State the population, period and action definition with the rate.

In practice: check that numerator, denominator and period describe the same journey.

Conversion rate optimization

Process of improving journeys and interfaces to increase completion of a useful action without weakening trust.

In practice: Segment by intent and device before comparing an overall rate that mixes different journeys.

Cookie

Small piece of data stored by the browser and returned according to HTTP scope, lifetime and context rules. It may support a session or preference without being advertising-related. Attributes, application uses and removal conditions need consideration together.

Reference: MDN : Using HTTP cookies · Source consulted 2026-10-18

In practice: Inventory each cookie’s purpose, lifetime and provider before writing visitor information.

Core update

Major update to a search engine’s core ranking systems that may change visibility across many websites.

In practice: compare pages and queries over several weeks before attributing a change to an update.

Core Web Vitals

Three real-experience metrics: LCP for loading, INP for responsiveness and CLS for visual stability. Good thresholds are respectively ≤ 2.5 s, ≤ 200 ms and ≤ 0.1 at the 75th percentile, with mobile and desktop assessed separately.

Reference: web.dev : Web Vitals · Source consulted 2026-10-21

In practice: examine LCP, INP and CLS across page families and distinguish lab results from real-visitor data.

Correlation identifier

Tracking identifier linking events from the same exchange across processing steps or services.

Reference: OWASP : Logging

Follow a synthetic request from receipt to result without recording its sensitive content in logs.

CORS

HTTP mechanism allowing a server to permit certain cross-origin browser access. It replaces neither authentication nor server-side permissions protecting the operation.

Reference: MDN : CORS

Source consulted : MDN · 2026-10-17

Test an allowed and a refused origin, then separately check account permissions for the requested operation.

Crawl budget

Amount of resources a search engine may devote to crawling a website over a given period. Distinguish crawling capacity from engine demand. Filter combinations and duplicates can multiply URLs to inspect without adding useful information.

Reference: Google Search Central · Crawl budget · Source consulted 2026-10-25

In practice: first look for unnecessary URL spaces and recurring errors on a large site.

Crawl trap

Structure generating a very large or infinite number of low-value URLs and unnecessarily trapping crawlers.

In practice: Find parameters or calendars producing endless addresses and limit their generation.

Crawler

Program automatically discovering and retrieving pages and resources by following URLs and links.

In practice: Examine identity and observed behaviour before attributing a visit to a particular engine.

Credential stuffing

Automated login attempts using username–password pairs stolen elsewhere. The attack exploits reuse across services rather than inventing every combination.

Reference: OWASP · Credential stuffing · Source consulted 2026-10-31

Source consulted : OWASP · Credential Stuffing Prevention · 2026-10-31

CRM

Customer Relationship Management: tool and method for centralizing contacts, conversations, opportunities and customer relationships.

In practice: define follow-up stages and truly useful data before configuring fields.

CSP

Policy sent to the browser to restrict resources a document can load or execute, among other controls. It can reduce certain injection opportunities. Test it against necessary resources; it complements rather than replaces safe data handling and other application checks.

Reference: MDN : Content Security Policy · Source consulted 2026-10-18

In practice: deploy a policy suited to actual resources and review reports before tightening it.

CSRF

Attack making a user’s browser perform an unwanted action on a site where they are authenticated. The request may appear legitimate to the server.

Reference: OWASP · Cross-Site Request Forgery Prevention · Source consulted 2026-10-31

Source consulted : MDN · CSRF · 2026-10-31

CSS

Language describing document presentation: layout, colours, spacing, typography and screen adaptations. The cascade determines which rules apply. A visual change does not transform an element’s HTML role: making text look like a button does not add button behaviour.

Reference: MDN : CSS · Source consulted 2026-10-18

In practice: check results on real components at important widths and interaction states.

CSV formula injection

Risk of an exported cell being interpreted as a formula when a file is opened in a spreadsheet.

Reference: OWASP : CSV Injection

Check exports using test cells and the actual software used, without executing a dangerous formula.

Cumulative Layout Shift

Cumulative Layout Shift (CLS): visual-instability metric based on unexpected element shifts. It can be affected after initial loading, for example when content is inserted late.

Reference: web.dev : Cumulative Layout Shift

Source consulted : web.dev : Cumulative Layout Shift · 2026-10-10

In practice: Find the element that moves during a real interaction and reserve stable space for it.

Cursor pagination

List traversal where a token returned by the service is used to request subsequent results.

Reference: Google : AIP-158 Pagination

Test the end of a list, an invalid token and a changed filter; specify when traversal must restart.

Customer journey

Customer journey: sequence of needs, interactions and decisions experienced before, during and after a conversion.

In practice: Record information sought before, during and after contact, including outside the website.

Cybersecurity

Measures intended to protect systems, data, services and users against digital threats.

Reference: NIST CSRC · Cybersecurity · Source consulted 2026-10-31

In practice: List critical assets, owners and response procedures before buying tools.