2.3.1: Three Flashes or Below Threshold
Guideline 2.3.1 ensures that web content does 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. This is crucial for preventing seizures in individuals with photosensitive epilepsy.
Importance of 2.3.1: Three Flashes or Below Threshold Success Criterion
Flashing content can trigger seizures in individuals with photosensitive epilepsy, making it a significant accessibility concern. By adhering to this guideline, web developers can create safer web environments for all users, particularly those with this condition. Limiting flashing content not only helps prevent serious health risks but also enhances user comfort and overall accessibility, promoting a more inclusive web experience.
Primary Use Cases and Requirements Under Guideline 2.3.1: Three Flashes or Below Threshold (Level A)
Use Case 1: Flashing Advertisements
Example: A website contains an advertisement banner that flashes rapidly to attract attention.
Control: Ensure the advertisement does not flash more than three times per second.
How to Test: Use a tool like the Photosensitive Epilepsy Analysis Tool (PEAT) to analyze the advertisement. Check that the flashing frequency is within the safe threshold. Verify the content manually by watching the advertisement and counting the flashes in a one-second interval.
Use Case 2: Video Content with Flashing Lights
Example: A music video embedded on a webpage contains scenes with strobe lights.
Control: Edit the video to reduce the frequency of flashing lights to comply with the guideline.
How to Test: Utilize video editing software to monitor the flashing sequences. Confirm the frequency is three flashes or below per second. Use PEAT to analyze the video and ensure it meets accessibility standards.
Use Case 3: Interactive Games
Example: An online game includes visual effects that flash rapidly during gameplay.
Control: Modify the game design to limit the flash frequency.
How to Test: Play the game and observe the flashing effects. Manually count the flashes to ensure they do not exceed three per second. Employ PEAT or a similar tool to analyze the game's visual effects for compliance.
Use Case 4: Animations on Webpages
Example: A webpage features a background animation with flashing elements.
Control: Adjust the animation to reduce the flash rate or replace it with a non-flashing alternative.
How to Test: Observe the animation and count the flashes within a one-second period. Use automated testing tools like PEAT to verify the animation's compliance with the guideline.
Testing Steps:
1. Manual Observation: Watch the flashing content for several seconds. Count the flashes in a one-second interval to ensure they do not exceed three flashes.
2. Automated Tools: Use tools like the Photosensitive Epilepsy Analysis Tool (PEAT) to analyze the flashing content. Ensure the content passes the general flash and red flash thresholds set by the tool.
3. Video Editing and Analysis: For video content, use video editing software to check and adjust the flash sequences. Reanalyze the edited content with PEAT to confirm compliance.