Glossary

Accessibility words, defined.

I write about accessibility for people who did not go looking for the subject. A city clerk who inherited the website. A shop owner who opened a demand letter. A director who was told the site has to be “ADA compliant” and was not told what that means.

This page defines the terms I use, in plain language, and where one of them gets used loosely or in the wrong place, I say so. If an entry is still unclear after you read it, that is my problem and not yours; tell me which one and I will expand the description.

Three different things with similar names

ADA is the law. WCAG is the technical standard the law points at. Section 508 is a different law that binds federal agencies and the vendors selling to them, and it is the one most likely to turn up in a document where it does not apply.

If you work for a Wisconsin city, county, or school district, your rule is ADA Title II and your standard is WCAG 2.1 Level AA. If you run a private business, your rule is ADA Title III, and no technical standard is written into that regulation. Section 508 is almost certainly not yours.

The terms

ACR (Accessibility Conformance Report)

The completed document a vendor hands you after measuring their product against an accessibility standard. A VPAT is the blank form; an ACR is that form filled in with real findings.

An ACR is a vendor’s report on itself. Read the “Supports with exceptions” and “Does not support” rows before you read the summary at the top.

ADA (Americans with Disabilities Act)

The 1990 federal civil rights law that prohibits discrimination on the basis of disability. Two of its titles reach websites: Title II covers state and local government, and Title III covers private businesses open to the public.

For most of the law’s life it named no technical standard for websites at all, which is why so much of the argument used to be about what “effective communication” means. Title II has a standard now. Title III still does not.

Alt text

The written description of an image, carried in the image’s alt attribute, that a screen reader speaks when it reaches the picture.

Alt text that is present is not the same as alt text that is useful. “IMG_4021.jpg” and “image” both satisfy an automated check for presence and tell a blind reader nothing. A purely decorative image should carry an empty alt attribute instead of a description, so the screen reader passes over it without comment.

ARIA (Accessible Rich Internet Applications)

A set of HTML attributes that tell assistive technology what a custom control is and what state it is in, for the cases where plain HTML cannot say so on its own.

ARIA is a last resort, not a first one. A real <button> announces itself correctly with no ARIA at all, while a <div> wearing role="button" needs keyboard handling that someone now has to write by hand. Wrong ARIA is worse than none, because it tells assistive technology something false with full confidence.

Assistive technology

The software or hardware someone uses to operate a computer: a screen reader, a screen magnifier, voice control, a switch device, a refreshable braille display, an alternative keyboard. Shortened to AT in most writing on the subject.

axe

The open-source testing engine, built by Deque Systems, that sits underneath most automated accessibility checkers. My audit runs it too, as one lane out of several.

axe is precise about what it can see and silent about everything else. A clean axe run is a floor, not a finish line.

Conformance, and how it differs from compliance

Conformance is a measurement: does this page meet every success criterion at the level being claimed? Compliance is a legal question: does this organization satisfy the law that applies to it?

The two come apart in both directions. A site can conform to WCAG 2.1 AA and still draw a complaint, and an organization can be in real legal trouble over a site nobody has ever measured. I report conformance. I am not a lawyer, and nothing here is legal advice.

Conformance level (A, AA, AAA)

WCAG sorts its success criteria into three levels. Level A is the minimum. Level AA is the working standard that laws and contracts name. Level AAA is a higher bar that W3C itself says is not required across an entire site.

The levels are cumulative rather than alternatives. Meeting AA means meeting every Level A criterion as well.

DOJ (Department of Justice)

The federal agency that enforces the ADA and writes its regulations. DOJ published the Title II web rule in April 2024, and an interim final rule in April 2026 that moved both deadlines back a year.

Focus order

The sequence keyboard focus travels through a page as someone presses Tab. It should follow the order the content reads in.

Focus order is a property of the HTML, not of the layout. Moving a block visually with CSS does not move it in the tab order, so a page that reads sensibly left to right on screen can tab in an order that makes no sense at all.

Keyboard trap

A place where focus goes in and cannot get back out with the keyboard alone. A video player or a modal dialog that captures Tab and never releases it strands anyone who does not use a mouse.

This is a Level A failure, which is to say it sits at the most basic bar there is.

Overlay

A third-party script that patches accessibility from the outside without changing the site underneath. In 2025 the FTC fined an overlay vendor $1 million over claims that its widget made sites conform to WCAG 2.1 AA; menus, headings, tables, and images still failed.

I do not install overlays.

POUR

The four principles WCAG is organized under: Perceivable, Operable, Understandable, Robust. Every success criterion sits beneath one of them.

POUR is a good way to think about why a particular barrier matters. It is not a checklist, because the work happens at the criterion level.

Remediation

Fixing the accessibility problems an audit found. The word carries a lot of weight in contracts and scopes, so it is worth pinning down whether a given use of it means code changes, content changes, or both.

Software that speaks the screen aloud, or sends it to a braille display, so someone can use a computer without seeing it. The common ones are JAWS and NVDA on Windows, VoiceOver on Mac and iOS, and TalkBack on Android.

Screen-reader users are not one audience with one setup. Two people running the same software, on the same page, navigate it differently, which is why testing with real users finds what no tool does.

Section 508

The part of the Rehabilitation Act that requires federal agencies to make their electronic and information technology accessible. The Access Board issued the refreshed standards in January 2017, and they took effect in January 2018. Their technical standard is WCAG 2.0, Levels A and AA.

It binds federal agencies and the vendors selling to them. It does not bind a private business or a Wisconsin city.

You will still see “Section 508 compliant” in an RFP, or on a vendor’s capability sheet, from an organization no part of Section 508 reaches. Most of the time that phrase got carried over from another document rather than traced back to a requirement. If one lands in front of you, the useful question is who wrote it and which standard they actually meant, and the answer is almost always WCAG.

The link at the very top of a page that jumps past the navigation straight to the main content. Without one, someone tabbing through has to pass every navigation link before reaching the article, on every page.

A skip link that exists in the HTML but never becomes visible when it receives focus fails at the one job it was added for. I test whether it actually paints, by comparing rendered pixels focused against unfocused, rather than by reading the stylesheet.

Success criterion (SC)

One testable requirement inside WCAG, written as a number: SC 1.1.1 Non-text Content, SC 2.4.7 Focus Visible. The plural is success criteria.

When a report says a page fails 1.4.3, that number is the address of one specific requirement, and it is what makes a finding checkable by someone other than the person who wrote it.

Title II

The part of the ADA covering state and local government: cities, counties, school districts, special districts, public colleges and technical colleges.

In April 2024 DOJ set a technical standard for their web content and mobile apps, WCAG 2.1 Level AA, at 28 CFR Part 35, Subpart H. After the April 2026 interim final rule, public entities serving 50,000 or more people have until April 26, 2027, and everyone else has until April 26, 2028, including every special district government regardless of its size.

Which date applies to you turns on three details, including which Census product counts. I wrote those up in ADA Title II and You.

Title III

The part of the ADA covering private businesses open to the public: shops, restaurants, clinics, hotels, gyms, and the websites that serve them.

Title III has been litigated continuously for years, it has no extension to ride, and no technical standard is written into the regulation the way one is written into Title II. That gap is why demand letters and settlements do the work a rule would otherwise do.

VPAT (Voluntary Product Accessibility Template)

The blank form, maintained by the Information Technology Industry Council, that a vendor fills in to report how their product measures against an accessibility standard. Filled in, it becomes an ACR.

A VPAT on its own is not an accessibility claim. Ask for the completed report, then read the exceptions.

W3C (World Wide Web Consortium)

The international body that develops web standards, HTML and WCAG among them.

WAI (Web Accessibility Initiative)

The part of W3C that produces the accessibility standards and the guidance around them. When a report links out to a page explaining what a success criterion means, that page is usually WAI’s.

WCAG (Web Content Accessibility Guidelines)

The technical standard that accessibility laws, contracts, and audits point at. W3C publishes it, and it arrives in versions: 2.0 in 2008, 2.1 in 2018, and 2.2 in 2023, each one adding criteria without retiring what came before. Most people say it as a word rather than spelling out the letters.

WCAG is not a law. It is the yardstick laws point at, which is how a rule published in 2024 can name WCAG 2.1 AA while the current version is 2.2.

I add terms to this page when someone asks about one. If you hit a word here, or anywhere else on this site, that this page does not cover, tell me and I will write it up.