A
Accessibility tree The accessibility tree is the structure a browser derives from a page and presents to assistive technology; it is the page a screen reader sees. Accessibility
Accessible name The accessible name is the name of an interface element as read by assistive technology, and it can differ from the text shown on screen. Accessibility
AEO (Answer Engine Optimization) is the practice of getting content selected as the unit that answers a question directly. Answer engines
AI Overviews is the AI-generated summary Google shows above the search results page, synthesised from more than one source. Answer engines
ARIA (Accessible Rich Internet Applications) is a set of attributes used to convey role, state and property information to assistive technology where HTML cannot express it on its own. Accessibility
What is ARIA?
ARIA is a set of attributes used to convey role, state and property information to assistive technology where HTML cannot express it on its own.
ARIA is a complement that steps in where semantic HTML falls short — not a replacement for it. That distinction is the most important rule about ARIA, and when it is misunderstood the result is worse than using no ARIA at all.
It conveys three things. The role says what an element is — a tab, a dialog, a progress bar. The state says what condition it is in at that moment — open or closed, selected or not, invalid. The property carries qualities that do not change — which element it controls, what text labels it.
The critical point is this: ARIA adds no behaviour. Giving an element the button role does not make it work with a keyboard; it only tells the screen reader “this is a button”. Keyboard support, focusability and key behaviour still have to be written. That is why using a real button element is always safer than imitating one with ARIA.
The first rule of the WAI-ARIA authoring guidance sums this up in a sentence: if there is a built-in HTML element that does the job, use it instead of ARIA. The second rule points the same way — do not override built-in semantics with ARIA.
- Declaring the wrong role is worse than declaring none — the screen reader has been told a lie.
- Forgetting to remove a visually hidden element from the accessibility tree leaves the user wandering through invisible content.
- Hiding an element while leaving it focusable produces a silent focus stop.
- Giving a label both natively and through ARIA creates a conflict; ARIA usually wins and the native label disappears silently.
The practical approach is this: choose the right HTML element first, notice that the behaviour comes free from the browser, and use ARIA only for the gap that remains. Components with no HTML equivalent — a tab group, an accordion, a custom dropdown — are where ARIA is genuinely required.
One place ARIA is commonly misused is in producing the accessible name. When an element is given both a native label and an ARIA label the two collide, and ARIA usually wins — the native label disappears silently. The text on screen and the text read out diverge, and someone using voice control cannot activate the element by saying the label they can see.
As a rule: before adding ARIA, ask “can this information already be derived from the HTML?” If the answer is yes, ARIA is unnecessary and adding it carries risk.
If you want to know whether your own site meets these criteria, our custom web design and development builds WCAG 2.2 AA in from the first draft — accessibility is part of the build, not a plugin.
Accessibility
B
Brand mention A brand mention is a brand’s name being named without a link, and in the era of answer engines it is a visibility signal independent of links. Answer engines
C
Cache header A cache header is the server response header that tells the browser how long a resource may be stored and how it is to be revalidated. Performance
Canonical address A canonical address is the markup declaring which page is the original when the same or very similar content is reachable from more than one address. Multilingual
Citation A citation is an answer engine mentioning a source in the answer it produces, usually with a link to it. Answer engines
CLS (Cumulative Layout Shift) measures how much content shifts unexpectedly while a page is loading or in use, and Google counts anything under 0.1 as good. Performance
Colour blindness is the inability to tell certain colours apart, and it affects a considerable share of the world’s population, men in particular. Accessibility
Compression is the shrinking of text-based resources before they are sent from the server and their expansion in the browser. Performance
Core Web Vitals is the collective name for the three metrics Google defined to measure a page’s real user experience. Performance
Country domain (ccTLD) A country domain is a two-letter top-level domain extension allocated to a particular country. Multilingual
Crawl budget is the number of requests a search engine allocates to fetching from a site within a given period. Answer engines
Critical rendering path The critical rendering path is the minimum sequence of steps a browser must complete before it can draw a page on screen. Performance
E
Entity An entity means a distinct thing that search and answer engines recognise — a person, an organisation, a place, a product or a concept. Answer engines
F
Field data is the sum of performance measurements experienced by real users on real devices and real networks. Performance
Focus trap A focus trap is when keyboard focus enters a region and cannot leave it again, and WCAG prohibits it explicitly at level A. Accessibility
Font subset A font subset is a font file regenerated with only the characters that are needed. Multilingual
G
GEO (Generative Engine Optimization) is the work of increasing the likelihood that a site is chosen as a source in the answers generated by AI systems. Answer engines
H
hreflang is the markup that declares a page’s different language and region versions to search engines. Multilingual
I
IndexNow is an open protocol that tells search engines immediately that a page has changed. Answer engines
INP (Interaction to Next Paint) is the time from a user interaction until the page responds visually, and Google counts anything under 200 milliseconds as good. Performance
J
JSON-LD (JavaScript Object Notation for Linked Data) is a structured data format that declares a page’s meaning in a machine-readable form without changing the page’s appearance at all. Answer engines
L
Language tag (BCP 47) A language tag is the standard coding form that tells machines which language a text is in. Multilingual
LCP (Largest Contentful Paint) is the paint time of the largest content element in a page’s visible area, and Google counts anything under 2.5 seconds as good. Performance
Live region A live region is an area of a page whose changes a screen reader has to announce to the user. Accessibility
llms.txt is an optional file placed in a website’s root directory that summarises, in Markdown, what the site is about and where its most important pages are for language models. Answer engines
Locale A locale is the setting that defines a user’s language and region together and determines the formatting rules. Multilingual
Localisation (Localization) is adapting content to the culture, habits and search language of a target market; it is a wider undertaking than translation. Multilingual
R
Reflow A reflow is the browser recomputing the positions and sizes of elements on a page after a change. Performance
Relative luminance is the value expressing a colour’s perceived lightness between 0 and 1, and it is the basis of the contrast ratio calculation. Accessibility
S
Screen reader A screen reader is assistive technology that turns on-screen content into speech or braille output and lets the user navigate by keyboard. Accessibility
Semantic HTML means choosing each element for its meaning rather than its appearance — a heading element for a heading, a button element for a button, a list element for a list. Accessibility
Structured data is an additional layer that labels a page’s content with a standard vocabulary machines can understand. Answer engines
T
Text expansion is the same content being of different lengths in different languages, and the layout having to flex accordingly. Multilingual
Translation memory A translation memory is a database that stores previously translated sentences and suggests them when the same or a similar sentence comes up again. Multilingual
TTFB (Time to First Byte) is the time between the browser sending a request and receiving the first byte from the server. Performance
W
WCAG (Web Content Accessibility Guidelines) is the international standard published by the W3C that defines the accessibility of web content through testable success criteria. Accessibility
X
x-default is a special hreflang value declaring the default page to show when no language version matches the user’s language. Multilingual