Testing for Three Flashes or Below Threshold

WCAG 2.0 SC 2.3.1 Level A requirement:

Web pages do not contain anything that flashes more than three times in any one second period, or the flash is below the general flash and red flash thresholds.

The following tests can be performed in any order, but have been listed according to the SC requirement. Passing any of these tests will meet SC 2.3.1:

• Test 1: if a flashing element has a frequency at or below 3 Hertz;
• Test 2: if a flashing component is smaller than the size threshold;
• Test 3: if a flashing component does not contain more than 3 general flashes or 3 red flashes in a second.

**These tests may not be safe for testers with sensitivity to flashing components.** These tests require extended viewing of flashing content. Testers are strongly encouraged to read the test descriptions and understand the warnings before performing any tests.

Test 1: The 3 Hertz Flasher

Determine if the frequency of the flashing component is 3 Hertz or below. If it is, then it meets the requirement.

**Warning: activating the bookmarklet will display flashing content on the screen.** Using this bookmarklet to test flashing content will result in multiple flashing elements on screen.

1. Add the 3Hz Flasher bookmarklet to your browser.
2. After the bookmarklet is installed, navigate to the web page to be tested.
3. Active the 3Hz Flasher bookmarklet to display an overlay with text that flashes at 3 Hz (3 times per second). This can be used as a reference to help determine whether something is flashing slower or faster than 3 Hz.
• If it is obviously flashing slower than the overlay text, then it is below the 3 hertz frequency requirement. It's conformant with SC 2.3.1. Further testing is not necessary.
• If page content is flashing faster than the overlay text, or it's close or too difficult to determine which is faster, continue to the next step for further testing.
4. To remove the flashing overlay text, refresh the page.

Test 2: Check the size of the flashing content

A flashing component must be either smaller than a size requirement or it must not contain a general flash or red flash. We will check the size requirement first since it's an easier test.

The flashing content meets the requirement if the combined area of flashes is smaller than a 341x256 pixel rectangle when the content is viewed at 1024 x 768 screen resolution.

1. Add the Flash Rectangle bookmarklet to your browser.
2. After the bookmarklet is installed, navigate to the web page to be tested.
3. Set your screen resolution to 1024 x 768.
4. Activate the Flash rectangle bookmarklet. Choose a vertical or horizontal orientation and drag the rectangle over the flashing content.
• If all of the combined flashing content can be covered by the rectangle, it is small enough and passes SC 2.3.1. Further testing is not necessary.
• If all of the combined flashing content can not be covered by the rectangle, continue to the next test.
5. To remove the flash rectangle, refresh the page.

Test 3: Check for a general flash or red flash

This final test step utilizes the values entered below (on this page) to compute the existence of a red or general flash. Obtain the RGB values of the component that flashes. This can be done by using the eye dropper tool of the Color Contrast Analyser (CCA) from the Paciello Group or a similar eye dropper tool.

**Warning: extended viewing of a flashing component is necessary to grab the colors with an eye dropper.**

1. Navigate to the page to be tested.
2. Open the eye dropper tool (CCA)
3. Select the Foreground eye dropper.
4. Place the eye dropper tool over the flashing element to select a color that is flashing. CCA will display the RGB values for that color. (If hex values are displayed, select "RGB" under the Options menu - Displayed color value.)
5. Use the Background eye dropper to select the opposing color of the flashing element.

Enter the RGB values for the two colors

Please enter RGB values for both colors. The range for each input is from 0 to 255, inclusive. Results will be provided in the next section.

Test Results for the entered color values: