Glossary
The vocabulary of digital decision systems, defined precisely and traced to specifications. Terms marked ⦿ live have a working instrument that demonstrates them.
28 of 28 terms
- Largest Contentful Paint (LCP)⦿ liveThe render time of the largest visible content element — the loading-speed Core Web Vital. Good ≤ 2.5 s at p75.Performance
- Interaction to Next Paint (INP)⦿ liveThe responsiveness Core Web Vital: full interaction latency through the next visual update. Replaced FID in 2024. Good ≤ 200 ms.Performance
- Cumulative Layout Shift (CLS)⦿ liveThe visual-stability Core Web Vital: the largest session window of unexpected layout shifts. Good ≤ 0.1.Performance
- Time to First Byte (TTFB)⦿ liveElapsed time from navigation start until the first byte of the response arrives — the server and network's share of loading delay.Performance
- Render-blocking resourceA stylesheet or synchronous script the browser must fetch and process before it can paint — a direct LCP tax.Performance
- stale-while-revalidateA Cache-Control extension (RFC 5861) that serves an expired cached response instantly while refreshing it in the background.Performance
- 75th percentile (p75)⦿ liveThe assessment point for Core Web Vitals field data: the experience at least three quarters of page loads meet or beat.Performance
- Accessibility treeThe parallel structure a browser derives from DOM, CSS, and ARIA that assistive technology actually reads.Accessibility
- Accessible nameThe single text label assistive technology announces for an element, computed by a W3C-specified algorithm.Accessibility
- Focus orderThe sequence keyboard focus follows through interactive elements — WCAG requires it to preserve meaning and operability.Accessibility
- ARIA roleThe WAI-ARIA attribute that declares what an element is to assistive technology — a promise of behavior, not a behavior.Accessibility
- Assistive technology (AT)Software and hardware — screen readers, magnifiers, switch devices — that consume the accessibility tree to operate interfaces.Accessibility
- Contrast ratio⦿ liveThe WCAG-defined luminance ratio between text and background: 4.5:1 minimum for body text at level AA.Accessibility
- Ad rank⦿ liveThe auction score that orders ad positions — in the classic model, bid × quality — and sets what the slot above pays.Advertising mechanics
- Generalized second-price auction (GSP)⦿ liveThe multi-slot auction behind most search advertising: each winner pays just enough to keep its position, not its own bid.Advertising mechanics
- First-price auction⦿ liveAn auction where winners pay exactly what they bid — the rule most programmatic display moved to in 2019.Advertising mechanics
- Learning phaseThe exploration period after a campaign change when a delivery algorithm spends budget gathering data before optimizing on it.Advertising mechanics
- Budget pacingThe control loop that spreads a fixed ad budget across a period, throttling auction entries to avoid early exhaustion.Advertising mechanics
- Frequency cappingA delivery constraint limiting how often one person sees the same ad within a window — an identity problem as much as a rule.Advertising mechanics
- Tool-calling loop⦿ liveThe cycle at the core of every AI agent: the model emits a structured tool call, the runtime executes it, the result re-enters context.AI systems
- Agent orchestration⦿ liveThe control layer above tool-calling loops: routing work across steps or agents, managing state, retries, and stopping rules.AI systems
- Answer engineA system that responds to queries with a synthesized, cited answer rather than a list of links — the AI search layer.AI systems
- Citation selectionHow an answer engine chooses which retrieved sources to cite — the mechanism that decides visibility in AI search.AI systems
- LLM evalsSystematic tests that measure model or agent behavior against defined expectations — the unit tests of AI systems.AI systems
- Event pipeline⦿ liveThe path a user interaction travels from client capture through collection, processing, and storage into reported numbers.Analytics & privacy
- Consent signal⦿ liveThe recorded user choice that gates what a site may collect — and the mechanism that decides which tags ever fire.Analytics & privacy
- Data minimisation⦿ liveThe privacy-by-design principle of collecting only what a stated purpose requires — a systems constraint, not a policy line.Analytics & privacy
- FingerprintingIdentifying a device by combining incidental signals — fonts, canvas, hardware — without storing any identifier on it.Analytics & privacy