Focusable Elements (Quick) - ally.js Compatibility Table

The following tables show the differences between what browsers consider focusable and what ally.js identifies using strategy: quick.

Note that touch devices (without a physical keyboard) only show elements as tabbable (keyboard focusable), that can be navigated to through the on-screen keyboard (or "virtual keyboard").

Document Elements
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`<html>` 2 1	inert -1	inert -1	focusable inert -1 E S	focusable inert -1 E S	tabbable inert 0	tabbable inert 0	tabbable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`<body>` 3 1	focusable inert -1 E S	focusable inert -1 E S	focusable inert -1 E S	focusable inert -1 E S	tabbable inert 0 E	tabbable inert 0	tabbable inert 0 E	focusable inert 0 E S	focusable inert 0 E S	focusable inert -1 E S	focusable inert -1 E S	focusable inert -1 E S	focusable inert -1 E S	focusable inert -1 E S	focusable inert -1 E S	focusable inert -1 E S

Label Element
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`<label for="…"> with <input id="…">` 6	redirecting -1 T	redirecting -1 T	redirecting -1 T	redirecting -1 T	inert redirecting 0 7	inert redirecting 0 7	inert redirecting 0 7	inert redirecting 0 7	inert redirecting 0	redirecting -1 T	redirecting -1 T	redirecting -1 T	redirecting -1 T	redirecting -1 T	redirecting -1 T	redirecting -1 T
`<label> with nested <input>` 6	redirecting -1 T	redirecting -1 T	redirecting -1 T	redirecting -1 T	inert redirecting 0 7	inert redirecting 0 7	inert redirecting 0 7	inert redirecting 0 7	inert redirecting 0	redirecting -1 T	redirecting -1 T	redirecting -1 T	redirecting -1 T	redirecting -1 T	redirecting -1 T	redirecting -1 T

Editable Elements
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`<span style="user-modify: read-write">` 8	tabbable inert 0	tabbable inert 0	inert -1	inert -1	inert 0	inert 0	inert 0	tabbable inert 0	tabbable inert 0	tabbable inert 0	tabbable inert 0	tabbable inert 0	tabbable inert 0	tabbable inert 0	focusable inert 0	tabbable inert 0

Image Maps
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`<area> with <img usemap="#…">`	inert 0 R	inert 0 R	tabbable inert 0 R	tabbable inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R
`<area> with <img usemap="#…" tabindex="-1">`	inert 0 R	inert 0 R	tabbable inert 0 R 14	tabbable inert 0 R 14	focusable inert 0 S R	focusable inert 0 S R	focusable inert 0 S R	focusable inert 0 S R	focusable inert 0 S R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R
`<input> between <img usemap="#map"> and <img usemap="#map">` 45	tabbable 0	tabbable 0	focusable tabbable 0 44	focusable tabbable 0 44	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	focusable 0	tabbable 0
`<area> child of <map name="#…"> with <object type="image/png" usemap="#…">`	inert 0 R	inert 0 R	focusable inert 0 R	focusable inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R
`<area href="…"> <object type="image/png" usemap="#…" >`	inert 0 R	inert 0 R	focusable inert 0 R	focusable inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R	inert 0 R

Shadow DOM
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`::shadow` 18 19	inert host inert -1 C	inert host inert -1 C	inert -1	inert -1	inert 0	inert 0	inert 0	inert 0	inert 0	inert host inert -1 C	inert -1	inert -1	inert -1	inert -1	inert host inert -1 C	inert -1
`<input tabindex="-1"> within ::shadow` 18 20	focusable -1 T R	focusable -1 T R	focusable inert -1 R	focusable inert -1 R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable -1 T R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable -1 T R	inert null M 67
`<input tabindex="0"> within ::shadow` 18 20	tabbable 0 T R	tabbable 0 T R	tabbable inert 0 R	tabbable inert 0 R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	inert null M 67	tabbable 0 T R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable 0 T R	inert null M 67
`<input tabindex="2"> within ::shadow` 18 20	tabbable 2 T R	tabbable 2 T R	tabbable inert 2 R	tabbable inert 2 R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	inert null M 67	tabbable 2 T R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable 2 T R	inert null M 67
`<input tabindex="1"> within ::shadow within ::shadow` 18 20	tabbable 1 T R	tabbable 1 T R	tabbable inert 1 R	tabbable inert 1 R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	inert null M 67	tabbable 1 T R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable 1 T R	inert null M 67
`<input tabindex="-1"> within ::shadow[tabindex="-1"]` 18 20 51	focusable -1 T R	focusable -1 T R	focusable inert -1 R	focusable inert -1 R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable -1 T R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable -1 T R	inert null M 67
`<input tabindex="0"> within ::shadow[tabindex="-1"]` 18 20 51	tabbable 0 T R	tabbable 0 T R	tabbable inert 0 R	tabbable inert 0 R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	inert null M 67	tabbable 0 T R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable 0 T R	inert null M 67
`<input tabindex="2"> within ::shadow[tabindex="-1"]` 18 20 51	tabbable 2 T R	tabbable 2 T R	tabbable inert 2 R	tabbable inert 2 R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	inert null M 67	tabbable 2 T R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable 2 T R	inert null M 67
`<input tabindex="1"> within ::shadow within ::shadow[tabindex="-1"]` 18 20 51	tabbable 1 T R	tabbable 1 T R	tabbable inert 1 R	tabbable inert 1 R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	inert null M 67	tabbable 1 T R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable 1 T R	inert null M 67
`<input tabindex="-1"> within ::shadow[tabindex="0"]` 18 20	focusable -1 T R	focusable -1 T R	focusable inert -1 R	focusable inert -1 R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable -1 T R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable -1 T R	inert null M 67
`<input tabindex="0"> within ::shadow[tabindex="0"]` 18 20	tabbable 0 T R	tabbable 0 T R	tabbable inert 0 R	tabbable inert 0 R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	inert null M 67	tabbable 0 T R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable 0 T R	inert null M 67
`<input tabindex="2"> within ::shadow[tabindex="0"]` 18 20	tabbable 2 T R	tabbable 2 T R	tabbable inert 2 R	tabbable inert 2 R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	inert null M 67	tabbable 2 T R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable 2 T R	inert null M 67
`<input tabindex="1"> within ::shadow within ::shadow[tabindex="0"]` 18 20	tabbable 1 T R	tabbable 1 T R	tabbable inert 1 R	tabbable inert 1 R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	inert null M 67	tabbable 1 T R	inert null M 67	inert null M 67	inert null M 67	inert null M 67	focusable 1 T R	inert null M 67

Iframe Element
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`<iframe src="…"> without focusable content` 21 22	tabbable focusable 0 S	tabbable focusable 0 S	tabbable focusable 0 E S C	tabbable focusable 0 E S C	focusable 0 C	focusable 0 C	focusable 0 C	focusable 0	focusable 0	tabbable focusable 0 S	tabbable focusable 0 S	tabbable focusable 0 S	tabbable focusable 0 S	tabbable focusable 0 S	focusable 0 S	focusable 0 S
`<iframe src="…"> with SVG document` 21 22	focusable 0 S C	focusable 0 S C	tabbable focusable 0 E S	tabbable focusable 0 E S	focusable 0	focusable 0	focusable 0	focusable 0	focusable 0	focusable 0 S C	focusable 0 S C	focusable 0 S C	focusable 0 S C	focusable 0 S C	focusable 0 S C	focusable 0 S C
`content in <iframe>` 21 22	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M

Object Element
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`<object type="application/x-shockwave-flash" data="…">` 31	focusable 0	focusable 0	focusable -1	focusable -1	inert 0	focusable tabbable 0 32	tabbable 0	tabbable 0	tabbable 0	focusable 0	focusable 0	focusable 0	focusable 0	focusable 0	focusable 0	focusable 0
`<object type="application/x-shockwave-flash" data="…" tabindex="0">` 31	focusable 0	focusable 0	tabbable 0	tabbable 0	inert 0	focusable tabbable 0 32	tabbable 0	tabbable 0	tabbable 0	focusable 0	focusable 0	focusable 0	focusable 0	focusable 0	focusable 0	focusable 0

SVG Element
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`<rect onfocus="">` 33 35	tabbable inert 0 34	tabbable inert 0 34	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	tabbable inert 0 34	tabbable inert 0	tabbable inert 0	tabbable inert 0 34	tabbable inert 0 34	focusable inert 0 34	focusable inert 0 34

SVG Document in Iframe Element
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`content in <iframe>` 21 22	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M

SVG Document in Embed Element
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`content in <embed>` 23 24	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M

SVG Document in Object Element
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`content in <object>` 25 26	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M

Details Element
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`<summary> within <details>` 38	tabbable 0	tabbable 0	inert -1	inert -1	inert 0	inert 0	inert 0	inert 0	inert 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	focusable tabbable 0 39	focusable 0	focusable 0
`<summary> within <details tabindex="-1">` 38	tabbable 0	tabbable 0	inert -1	inert -1	inert 0	inert 0	inert 0	inert 0	inert 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	focusable tabbable 0 39	focusable 0	focusable 0
`<a href="…"> within <details open>` 38	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	focusable tabbable 0 39	focusable 0	focusable 0
`<summary> within <details open>` 38	tabbable 0	tabbable 0	inert -1	inert -1	inert 0	inert 0	inert 0	inert 0	inert 0	tabbable 0	tabbable 0	tabbable 0	tabbable 0	focusable tabbable 0 39	focusable 0	focusable 0

Scrollable Elements
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`<div> child of horizontally overflowing <div style="overflow: auto">`	inert -1	inert -1	inert -1	inert -1	focusable inert 0	focusable inert 0	focusable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`<div> child of overflowing <div style="overflow: hidden">`	inert -1	inert -1	inert -1	inert -1	focusable inert 0	focusable inert 0	focusable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`<div> child of overflowing <div style="overflow: scroll">`	inert -1	inert -1	inert -1	inert -1	focusable inert 0	focusable inert 0	focusable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`<div> child of overflowing <div style="overflow: visible">`	inert -1	inert -1	inert -1	inert -1	focusable inert 0	focusable inert 0	focusable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`<div> child of not overflowing <div style="overflow: scroll">`	inert -1	inert -1	inert -1	inert -1	focusable inert 0	focusable inert 0	focusable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`<div> child of not overflowing <div style="overflow: scroll">`	inert -1	inert -1	inert -1	inert -1	focusable inert 0	focusable inert 0	focusable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`horizontally overflowing <div style="overflow: auto">`	inert -1	inert -1	tabbable inert -1	tabbable inert -1	focusable inert 0	focusable inert 0	focusable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`overflowing <div style="overflow: hidden">`	inert -1	inert -1	inert -1	inert -1	focusable inert 0	focusable inert 0	focusable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`overflowing <div style="overflow: scroll">`	inert -1	inert -1	tabbable inert -1	tabbable inert -1	focusable inert 0	focusable inert 0	focusable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`overflowing <div style="overflow: visible">`	inert -1	inert -1	inert -1	inert -1	focusable inert 0	focusable inert 0	focusable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`not overflowing <div style="overflow: auto">`	inert -1	inert -1	tabbable inert -1	tabbable inert -1	focusable inert 0	focusable inert 0	focusable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`overflowing <section style="overflow: scroll">`	inert -1	inert -1	tabbable inert -1	tabbable inert -1	inert 0	inert 0 40	inert 0 40	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`<div> child of <div style="overflow: scroll" tabindex="-1">`	inert -1	inert -1	inert -1	inert -1	focusable inert 0	focusable inert 0	focusable inert 0	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1

Image Element Ismap Attribute
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`<img ismap src="…"> child of <a href="…">`	inert -1	inert -1	inert -1	inert -1	tabbable inert 0 41	tabbable inert 0 41	tabbable inert 0 41	tabbable inert 0 41	tabbable inert 0 41	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`<img ismap src="…"> child of <a href="…" tabindex="-1">`	inert -1	inert -1	inert -1	inert -1	tabbable inert 0 41	tabbable inert 0 41	tabbable inert 0 41	tabbable inert 0 41	tabbable inert 0 41	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1

CSS Flexbox Layout
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`<span> child of <a href="…" style="display: flex">`	inert -1	inert -1	inert -1	inert -1	inert 0	focusable inert 0 42	focusable inert 0 42	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`<span> child of <div tabindex="-1" style="display: flex">`	inert -1	inert -1	inert -1	inert -1	inert 0	focusable inert 0 42	focusable inert 0 42	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`<span style="display: flex">`	inert -1	inert -1	inert -1	inert -1	inert 0	focusable inert 0 42	focusable inert 0 42	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`<span> child of <span style="display: flex">`	inert -1	inert -1	inert -1	inert -1	inert 0	focusable inert 0 42	focusable inert 0 42	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1
`<span style="order: 1"> with focusable child`	inert -1	inert -1	inert -1	inert -1	inert 0	focusable inert 0 42	focusable inert 0 42	inert 0	inert 0	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1	inert -1

Questionable Elements
Element	Chrome		Firefox		IE					Opera	Safari			WebKit Nightly	Chrome Mobile (Android)	Safari (iOS)
Element	47.0	49.0	43.0	46.0	9.0	10.0	11.0	12.10240	13.11082	34.0	6.2	8.0	9.0	602.1	47.0	9.0
`<keygen …>` 47 48	inert null M	inert null M	inert null M 46	inert null M 46	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M	inert null M

Footnotes

The DOM Element Interface is missing the focus method.
The focus event is not emitted upon the element becoming the active element (document.activeElement).
The :focus CSS pseudo class is not set on the element when it is the active element (document.activeElement).
The element becomes the active element (document.activeElement) when an element of contentDocument or the shadowRoot has focus.
Note 1

Considering the <html> and <body> element focusable should have no benefit to a website (unless explicitly made focusable by adding the tabindex attribute), which is why ally.js considers the <html> and <body> element inert.
Note 2

The <html> element itself is not considered focusable, but some browsers may give it focus when focus is passed from browser UI to the document.
Note 3

The <body> element itself is not considered focusable, but it is has focus (i.e. is document.activeElement) if no other element has focus.
Note 6

The activation behavior of the <label> element is not defined beyond »… should match the platform's label behavior.«
Note 7

Internet Explorer redirects focus from <label> to the referenced form control element upon mouse click, but not on script focus via element.focus().
Note 8

The CSS property user-modify was proposed and dropped from CSS UI Level 3 and has thus not become a standard yet.
Note 14

If an <area> element doesn't have an href attribute, it's not a link (and should therefore not be interactive).
Note 18

Shadow DOM is currently only "properly" supported in Blink based browsers (Chrome, Opera). Firefox exposes the (considerably buggy) development state behind flags.

See Can I Use.
Note 19

Regardless of its own focusable state, an element hosting a Shadow DOM can become the activeElement if an element inside the ShadowRoot has focus. See Shadow DOM - Active Element
Note 20

The activeElement is scoped within the Shadow DOM, meaning the master documet does not know which shadowed content currently has focus. To indicate that a shadowed element has focus, the element hosting the shadowed content is made the activeElement regardless of its ability to receive focus otherwise.
Note 21

Technically the content of an iframe can be accessible to script.
Note 22

Because of the Same Origin Policy we can't reliably look inside <iframe>s to determine their content, which is why ally.js considers all <iframe> content inert
Note 23

There is no API to interact with the content document of an <embed> element
Note 24

Because there is no API to dive into the content document of an <embed> element, ally.js considers all <embed> content inert.
Note 25

Technically the content of an <object> element can be accessible to script.
Note 26

Because of the Same Origin Policy we can't reliably look inside <object>s to determine their content, which is why ally.js considers all <object> content inert.
Note 31

The behavior of the <object> element depends on the content it presents. The most common content types used with <object> are SVG and SWF.
Note 32

This element is actually tabbable (keyboard focusable).

But when tabbing to it, the <kbd>Tab</kbd> behavior for the entire document breaks, as focus remains stuck on the browser UI.

This might be related to Trident 1109008.
Note 33

SVG 1.1 does not specify much in respect to accessibility. SVG 2 will bring the tabindex attribute. SVG Tiny 1.2 knows the focusable attribute.
Note 34

By registering a focus event listener the element becomes focusable. Blink 445798, WebKit 140024.

This is undetectable because elements don't provide a list of their registered event handlers.
Note 35

Elements made focusable by way of adding a focus event listener cannot be identified by ally.js
Note 38

The <details> element is specified in HTML 5.1, but not implemented everywhere.
Note 39

This element should be keyboard focusable (tabbable), but is currently only focusable because of WebKit 151767
Note 40

Internet Explorer turns <div> and <span> elements focusable when they're scrollable, but does not do the same for other sectioning or block-level elements
Note 41

The ismap attribute makes the <img> focusable (in addition to the parent <a>)
Note 42

There is no indication that the focusability of an element can be inherited by its children, let alone triggered by flexbox layout.
Note 44

Firefox may hide elements from the document's tabbing sequence if they're enclosed by two images referencing the same image map - Gecko 1116126.
Note 45

This test is not about an element's focusable state, but about potentially content that's potentially hidden from the tabbing sequence.
Note 46

Firefox transforms <keygen> to <select _moz-type="-mozilla-keygen"> while parsing HTML.
Note 47

The <keygen> element is poorly supported, practically never used and has seen intent to deprecate
Note 48

Because the <keygen> element is poorly supported, ally considers all <keygen> elements focus-relevant but not focusable.
Note 51

The focusable state of content elements in Shadow DOM are not affected by tabindex="-1" on the shadow host, contrary to the behavior of browsing contexts (<iframe>, <object>, <element>).
Note 52

Focus is redirected to the labeled control.
Note 53

Focus is redirected to the nested labeled control.
Note 60

Whenever an element within a ShadowRoot has focus, the element hosting the ShadowRoot is considered the activeElement of the document, as per the active element adjustment algorithm.

Firefox' Shadow DOM implementation still has a few problems: Gecko 1117535, Gecko 1117544, Gecko 1117552.
Note 67

This element could not be tested in this browser.
Note 68

When this element is the activeElement, the reference element <img usemap="…"> has the following state:
- is not the activeElement in its context
- does not have the :focus CSS pseudo class applied
- does not receive a focus event
Note 69

When this element is the activeElement, the reference element <img usemap="…"> has the following state:
- is not the activeElement in its context
- does not have the :focus CSS pseudo class applied
- receives a focus event
Note 70

When this element is the activeElement, the reference element <img usemap="…"> has the following state:
- is not the activeElement in its context
- has the :focus CSS pseudo class applied
- receives a focus event
Note 78

When this element is the activeElement, the reference element <object usemap="…"> has the following state:
- is not the activeElement in its context
- does not have the :focus CSS pseudo class applied
- does not receive a focus event
Note 79

When this element is the activeElement, the reference element <object usemap="…"> has the following state:
- is not the activeElement in its context
- does not have the :focus CSS pseudo class applied
- receives a focus event
Note 85

When this element is the activeElement, the reference element ShadowHost has the following state:
- is the activeElement in its context
- does not have the :focus CSS pseudo class applied
- receives a focus event
Note 86

When this element is the activeElement, the reference element ShadowHost has the following state:
- is not the activeElement in its context
- does not have the :focus CSS pseudo class applied
- receives a focus event

Focusable Elements (Quick) - ally.js Compatibility Table

Footnotes

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