Web Accessibility Checker : Check Details

Element

img

Error Type

Potential

Guidelines

BITV 1.0 (Level 2)
Level 1
7.1 Until user agents allow users to control flickering, avoid causing the screen to flicker.
Section 508
J - avoid flicker
Stanca Act
Requirement 5: Flicker
WCAG 1.0 (Level A)
Priority 1
7.1 Until user agents allow users to control flickering, avoid causing the screen to flicker.
WCAG 1.0 (Level AA)
Priority 1
7.1 Until user agents allow users to control flickering, avoid causing the screen to flicker.
WCAG 1.0 (Level AAA)
Priority 1
7.1 Until user agents allow users to control flickering, avoid causing the screen to flicker.
WCAG 2.0 (Level A)
2.3 Seizures: Do not design content in a way that is known to cause seizures.
Success Criteria 2.3.1 Three Flashes or Below Threshold (A)
WCAG 2.0 (Level AA)
2.3 Seizures: Do not design content in a way that is known to cause seizures.
Success Criteria 2.3.1 Three Flashes or Below Threshold (A)
WCAG 2.0 (Level AAA)
2.3 Seizures: Do not design content in a way that is known to cause seizures.
Success Criteria 2.3.1 Three Flashes or Below Threshold (A)

Requirement

All img elements have associated images that do not flicker.

Error

Image (GIF) may flicker.

Short Description

This error is generated for all img elements that contain a src attribute value that ends with ".gif" (case insensitive). and have a width and height larger than 25.

Rationale

People with photosensitive epilepsy can have seizures triggered by flickering or flashing in the 4 to 59 flashes per second (Hertz) range with a peak sensitivity at 20 flashes per second as well as quick changes from dark to light (like strobe lights).

How To Determine

Question	Does this image flicker?
PASS	Image does not flicker.
FAIL	Image does flicker.

Steps To Check

Procedure

1. Check each img element that has a src attribute value ending in '.gif'.
2. View the associated image and determine if it flickers using the general flash threshold and red flash threshold.

Expected Result

1. All img elements have associated images that do not flicker.

Failed Result

1. Use another image that does not flicker.

Examples

Pass Examples

Image does not flicker.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/REC-html40/strict.dtd">
<html lang="en">
<head>
<title>ATRC Testfile - Check #10.2 - Negative</title>
</head>
<body>
<img src="rex.gif" alt="A brown and black cat named Rex."/>
</body>
</html>

Fail Examples

Image flickers.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/REC-html40/strict.dtd">
<html lang="en">
<head>
<title>ATRC Testfile - Check #10.1 - Positive</title>
</head>
<body>
<img src="eatatjoes.gif" alt="eat at Joes" width="200" height="200"/>
</body>
</html>