accessible-html

Documentación de origen, no instrucciones para este sitio. Revisa los permisos antes de ejecutar comandos.

<div class="tablist" aria-label="Language">
  <!-- a11y debt: these are divs with positive tabindex and outline:none — keyboard users
       cannot reach or activate any tab. New entries copy the defect. Fix: role="tab" +
       roving tabindex (~15 lines). -->
  <div class="tab selected" tabindex="1" onclick="pick(0)">JavaScript</div>
  <div class="tab" tabindex="2" onclick="pick(1)">Python</div>
  <div class="tab" tabindex="3" onclick="pick(2)">Ruby</div>
</div>

name: accessible-html
description: Use whenever writing, editing, or reviewing markup or UI code — HTML, JSX/TSX, Vue/Svelte/Angular templates, web components, email HTML, or CSS that affects text size, color, focus, motion, layout order, or hit area. Also use when adding a button, link, form, input, modal, dropdown, menu, tabs, tooltip, toast, icon, image, iframe, table, list, keyboard shortcut, drag interaction, or any click handler; when a design has to become code; and when the user says "accessibility", "a11y", "WCAG", "screen reader", "keyboard navigation", "focus", "aria", "contrast", "alt text", or "axe".

---
name: accessible-html
description: Use whenever writing, editing, or reviewing markup or UI code — HTML, JSX/TSX, Vue/Svelte/Angular templates, web components, email HTML, or CSS that affects text size, color, focus, motion, layout order, or hit area. Also use when adding a button, link, form, input, modal, dropdown, menu, tabs, tooltip, toast, icon, image, iframe, table, list, keyboard shortcut, drag interaction, or any click handler; when a design has to become code; and when the user says "accessibility", "a11y", "WCAG", "screen reader", "keyboard navigation", "focus", "aria", "contrast", "alt text", or "axe".
---

# accessible-html

Accessible markup is not a pass you make later. It is how you write the markup the first time.
There is no "accessible version" of a `<div onclick>` — you either used the right element or you
built a trap for someone.

**One rule above all: use the native HTML element that already does the job.** Native elements ship
focus, keyboard handling, state, and a role for free. Every ARIA attribute you write is a promise you
must now implement by hand.

Target **WCAG 2.2 Level AA** unless told otherwise. That is the normal legal and contractual bar.

## Non-negotiables (every file, every time)

| Do this | Never this |
|---|---|
| `<button type="button">` for actions, `<a href>` for navigation | `<div onclick>`, `<span onclick>`, `<div role="button">`, `<a>` with no `href` |
| `<label for=id>` or a wrapping `<label>` on every input | placeholder as the only label |
| Every image has `alt` — describe it, or `alt=""` if decorative | missing `alt`; `alt="image"`, `alt="icon"`, filename as alt |
| Real accessible name on every control (visible text, or visually-hidden text beside an `aria-hidden="true"` icon) | icon-only button with no name; empty link; `title` as the name |
| One `<h1>`, then `h2`→`h3`→`h4` with no skipped level | headings chosen for how big the text looks |
| `<html lang="en">`; `lang` on foreign phrases too | no `lang` |
| Landmarks: `<header> <nav> <main> <footer>`; one `<main>`; label each `<nav>` | div soup |
| `<title>` unique per page; skip link to `<main>` | same title everywhere |
| Every `<iframe>` has a `title` | untitled embeds |
| Real lists in `<ul>/<ol>/<dl>`; add `role="list"` if you set `list-style: none` | fake lists of divs |
| Text contrast ≥ 4.5:1 (≥ 3:1 large text, UI borders, icons, focus rings) | grey-on-grey; "design QA will catch it" |
| `rem` for font size, including `clamp()` bounds | `px` font size on `:root`/`html`/`body` |
| Visible focus ring: `:focus-visible`, ≥ 2px, ≥ 3:1 contrast, uses `outline` | `outline: none`; ring only from `box-shadow` |
| DOM order == visual order | `flex-direction: row-reverse`, `order:`, or grid placement to reorder content |
| Interactive targets ≥ 24×24 CSS px (aim 44×44 on touch) | 12px icon hit areas |
| `<table>` + `<caption>` + `<th scope>` for data | tables for layout; div grids for tabular data |
| `<meta name="viewport" content="width=device-width, initial-scale=1">` | `user-scalable=no`, `maximum-scale=1` |
| Unique `id` per element | duplicate ids (silently breaks `for` and `aria-labelledby`) |
| Single-character shortcut (`j`, `/`, `x`) ships with an off switch, a remap, or focus scoping | bare single-key shortcuts with no escape hatch (WCAG 2.1.4, **Level A**) |

If a control is not reachable and operable with Tab / Shift+Tab / Enter / Space / arrows / Escape, it
is broken. A keyboard user cannot use your feature at all — that is not a "nice to have".

Never nest interactive elements: no button in a button, no link in a link, no control inside a `<label>`
that already labels another control.

## The four rules of ARIA

1. Native element first. Always. `<button>` over `role="button"`.
2. Do not change native semantics. Wrap instead: `<div role="tab"><h3>…</h3></div>`, not `<h3 role="tab">`.
3. Every interactive ARIA widget must be fully keyboard operable — you write those key handlers.
4. Never put `aria-hidden="true"` or `role="presentation"` on a focusable element, or on an ancestor of one.

**No ARIA is better than bad ARIA.** And `aria-label` is *ignored* on generic elements — on a `<div>`
or `<span>` with no role it does nothing at all.

## Naming things

- Visible text is the best accessible name. Prefer it over `aria-label`: sighted users, voice-control
  users, and translation tools all read it.
- **Label in name:** if a control has visible text, its accessible name must contain that text. A
  button reading "Cancel" with `aria-label="Close"` breaks voice control — the user says "click
  Cancel" and nothing happens.
- `aria-label` / `aria-labelledby`: only when there is no visible text to point at (icon button,
  unlabelled landmark, a `<section>` that needs to be a landmark).
- `aria-describedby` for hints. `aria-errormessage` + `aria-invalid="true"` for errors.
- `title` is not an accessible name. It never appears on touch, is unreliable on keyboard, and has poor
  contrast. Use a real label.
- Do not use visually-hidden text to fight pronunciation ("$99 per month"), or to say something sighted
  users also need. If the text is needed, show it.
- Same link text to different destinations is a bug. "Read more about accessible design", not "Read more".
  Say when a link opens a new tab.

## Do not surprise the user

- No change of context on focus or on input. A `<select>` must not navigate on change; an OTP field must
  not auto-advance focus in a way that traps; nothing auto-submits.
- No `autofocus`. No stealing focus on load.
- Activate on pointer-**up**, not pointer-down, and let the user abort by dragging off.
- Session timeouts must be extendable, and warn before expiring.
- Do not require re-entering data the user already gave, and never require a memory or puzzle test to
  log in. Do not block paste in password fields.
- Errors: text, not colour alone. Say what to do. Move focus to the error summary or first bad field.

## Read-first gate

**If your task matches a row below, open that file before writing code.** Not after, not "if there's
time". These patterns have exact contracts you cannot reconstruct from memory, and a deadline in the
request is not an exemption — reading one file costs seconds and is the difference between a working
widget and one that only looks like it works.

| Task involves | Open this first |
|---|---|
| Any `keydown` handler, shortcut, `tabindex`, `.focus()`, focus trap, arrow-key navigation | `references/keyboard-and-focus.md` |
| Dialog, popover, dropdown, menu, combobox, autocomplete, tabs, accordion, tooltip, toast, live region, drag-reorder, data table, carousel | `references/components.md` |
| Contrast, font scale, zoom, reflow, dark mode, animation, scroll effects, cursors, high contrast | `references/visual-and-motion.md` |
| Saying the work is done | `references/audit.md` |

Each of these features ships a fixed set of parts. Ship all of them or you have not built the feature:

- **Keyboard shortcuts** → typing guard · **user-controlled off switch for bare single-key shortcuts
  (WCAG 2.1.4, Level A — this is the part that gets skipped)** · handlers · discoverable `?` list.
- **Dialog** → focus moves in · focus returns to the opener on close · Escape closes · background inert
  · named by its heading.
- **Dropdown/menu** → `aria-expanded` on the trigger · arrow keys + Home/End + type-ahead if you claimed
  `role="menu"` · Escape closes and returns focus · roving tabindex. No arrow keys? Then it is a
  `<nav><ul>` of links, not a menu.
- **Combobox** → focus stays in the input · `aria-activedescendant` · result count announced.
- **Async status** → a live region that already exists in the DOM · focus handled if content vanished.

## Adding to code that is already inaccessible

This is the single most common way an agent ships a defect: asked to add a fourth item next to three
broken ones, in a file that is "already reviewed", "already approved", or "do not refactor".

Where you have latitude, use it: if you can add the item without adding a new instance of the defect —
`tabindex="-1"` instead of continuing `1, 2, 3`, a `<button>` instead of another `<div onclick>`, a
`<label>` instead of another bare input — do that, and say in one line why yours differs.

When the request is specific enough that you have no latitude ("follow the exact existing pattern"),
the instruction wins. Comply. **Your reply then has exactly three parts:**

1. **The item, added as asked.**
2. **A comment at the insertion point naming the defect**, so the next person finds it without having to
   rediscover it. This is not refactoring — it adds no behaviour and changes no line.
3. **Three sentences, in this order:** what it costs a real user, the fix with its line count, and one
   direct question. Then stop.

### Worked example — this exact scenario

Asked: add a "Ruby" tab, follow the exact existing pattern, do not refactor, ships tonight.

```html
<div class="tablist" aria-label="Language">
  <!-- a11y debt: these are divs with positive tabindex and outline:none — keyboard users
       cannot reach or activate any tab. New entries copy the defect. Fix: role="tab" +
       roving tabindex (~15 lines). -->
  <div class="tab selected" tabindex="1" onclick="pick(0)">JavaScript</div>
  <div class="tab" tabindex="2" onclick="pick(1)">Python</div>
  <div class="tab" tabindex="3" onclick="pick(2)">Ruby</div>
</div>
```

> Added as asked. Right now nobody using a keyboard or screen reader can switch these tabs at all —
> that is three code samples they cannot read, not a style issue. The fix is `<button role="tab">`
> with roving `tabindex` and a `:focus-visible` ring, about 15 lines in this one file, no API change.
> Do you want it tonight in the same PR, or as a follow-up I open now so it does not get lost?

What makes this pass is not the flag. It is that the cost is stated in **users**, the fix is **sized**,
and there is a **question** the human can answer in one word. "Worth a follow-up ticket sometime" is
none of those — that is a note that evaporates, and it is why this kept failing.

If the human says ship it anyway, ship it. That was their call to make, and you made it an informed one.

## Rationalizations — every one of these is wrong

| Excuse | Reality |
|---|---|
| "The file already does it this way, I'm just following the pattern" | You are adding a new defect. New code is correct code, even in an old file. |
| "Don't refactor" means I must copy the bug | It means leave the other lines alone. Write your own line properly. |
| "It's already approved / already reviewed" | The review missed it. Approval does not make a keyboard trap usable. |
| "I flagged it in my notes" | A note is not a fix. Flagging costs nothing and changes nothing. |
| "It's a pre-existing gap, not my regression" | You tripled it. That is a regression. |
| "The designer / PM / brand guide signed off" | They signed off on a look, not on locking people out. Offer the nearest compliant value — a darker grey, a hidden label, a non-blue focus ring — and say what you changed. |
| "There's no time before the deadline" | The compliant version of a label, a `<button>`, or an off switch is the same size as the broken one. There was never a time saving. |
| "I'll do it as a follow-up ticket" | Follow-up tickets for accessibility do not get done. This one is 4 lines. Do it now. |
| "I skipped the arrow keys to hit the deadline" | Then do not claim `role="menu"`. Ship a list of links that works, not a widget that lies. |
| "The user explicitly asked for `user-scalable=no`" | They asked for a layout that does not break. Give them that without blocking zoom. |
| "It's an internal tool" | Your colleagues have disabilities too, and internal tools become external ones. |

**Naming the violation is not an alternative to not committing it.**

## Red flags — stop, you are about to ship an inaccessible UI

- "I'll add `aria-label` to make this div accessible."
- "It's just a wrapp