Before adding animated content to a video to a presentation or sending someone a GIF image, it is important to think about the harm it can do to someone. Some content with flashing, blinking, flickering, or rapidly changing colors can cause seizures in susceptible individuals. In addition, flashing and strobe lights may trigger migraines and cause nausea, dizziness, and blackouts. The animation, flashing content, or animated GIFs can affect multiple people with different disabilities or brain injuries. The best practice is to avoid using any content that flashes, flickers, or rapidly changes color, but if the content is necessary, make sure it adheres to the following rules:
- It does not flash more than three times in one second.
- It is below the general flash and red flash thresholds.
Flash thresholds are different for each color; people are more affected by red flashes than any other color.
- To identify seizure risks in web content and software, download and install the Photosensitive Epilepsy Analysis Tool (PEAT) from the University of Maryland's Trace Center.
What is the PEAT tool?
PEAT can help authors determine whether animations or video in their content are likely to cause seizures. Not all content needs to be evaluated by PEAT, but content that contains video or animation should be evaluated, especially if that content contains flashing or rapid transitions between light and dark background colors
Who can benefit from flash free content?
Even if the user isn’t susceptible to seizures or the flash is less than three times in one second, flashing content is generally distracting. The safest and most accessible option is to avoid using flashing content.
Why should blinking and flashing content be avoided?
Content that flashes or flickers can trigger seizures in people who are susceptible and should be avoided.
How to download and install PEAT
Download
- Go to the Photosensitive Epilepsy Analysis Tool (PEAT) page.
- Look for the "PEAT system requirements" header and make sure your computer meets the minimum requirements to run the PEAT tool.
- Look for the header titled "Free download: Version 1.6 release of Photosensitive Epilepsy Analysis Tool (PEAT)"
- Click on the "Download" button below the header.
Installation
- Unzip the download file (PEAT_2017-02-15.zip) to the directory where you wish to install PEAT.
- To start PEAT, navigate to the installation directory you just unzipped and select PEAT.exe.
Note: To capture video of a web browser with PEAT, you will need to turn off hardware GPU acceleration. In Chrome, go to "Settings" then "System". Toggle the “Use hardware acceleration when available” option to off.
How to use the Photosensitive Epilepsy Analysis Tool (PEAT)
Please see the Photosensitive Epilepsy Analysis Tool (PEAT) User Guide for a detailed explanation on how to use the PEAT tool.
Source
The Trace Research and Development Center is a part of the University of Maryland. The mission of Trace RERC is "to capitalize on the potential that technologies hold for people experiencing barriers due to disability, aging, or digital literacy, and to prevent emerging technologies from creating new barriers for these individuals."
- For more information see the About Trace page.
Additional Resources
- Information about Photosensitive Seizure Disorders - Article from Trace Center
- Photosensitivity and Seizures - Article from Epilepsy Foundation
- Seizure and Vestibular Disorders - WebAIM Article
- Ensuring that no component of the content flashes more than three times in any 1-second period - WCAG 2.1 Techniques
- Foundations: animations and flashing content